CA1281227C - Emulsions and photographic elements containing silver halide grains having icositetrahedral crystal faces - Google Patents

Abstract

EMULSIONS AND PHOTOGRAPHIC ELEMENTS CONTAINING SILVER
HALIDE GRAINS HAVING ICOSITETRAHEDRAL CRYSTAL FACES
Abstract of the Disclosure Silver halide photographic emulsions are disclosed comprised of radiation sensitive silver halide grains of a cubic crystal lattice structure comprised of icositetrahedral crystal faces.

Description

EMULSIONS AND PHOTOGRAPHIC ELEMENTS CONTAINING SILVER
~ALIDE GRAINS HAVI~G ICOSITETRAHEDRAL CRYSTAL FACES
Field of the Invention This invention relates to photography. More specifically, this invention is directed to photographic emulsions containing silver halide grains and to photographic elements containing these emulsions.
Brief Description ~ the Drawing~
Figure 1 is an isometric view of a regular cubic silver halide grain;
Figure 2 is a æchematic diagram of the atomic arrangement at a silver bromide cubic crystal surface;
Figure 3 is an isometric view of a regular octahedral silver halide grain;
Figure 4 is a schematic diagram of the atomic arrangement at a silver bromide octahedral crystal surface;
Figure 5 is an isometric view of a re~ular rhombic dodecahedron;
Figure 6 is a schematic diagram of the atomic arrangement at a silver bromide rhombic dodecahedral crystal surface;
Figure 7 is an isometric view of a regular cubic silver halide grain, a regular octahedral silver halide grain, and intermediate cubo-octahedral silver halide grains.
Figures 8 and 9 are front and rear isometric views of a regular {211} icositetrahedron;
Figures 10 and 11 are schematic diagrams of theorized atomic arrangements at silver bromide icositetrahedral crystal surfaces of Miller indices of {211} and {533}, respectively;
Figures 12 through 27 and 31B are electron 35 micrographs of icositetrahedral silver halide grains;
Figures 28, 29B, 29C, 30C, 30D, and 31A are electron micrographæ of silver halide grains having 8~ 7 icositetrahedral protrusions on host grains;
Figures 29A, 30A, and 30B are electron mlcrographs of tabular grain emul6ions without icositetrahedral protrusions;
Figures 32A and 32B are plots of image density versus wavelength of exposure; and Figures 29A, 30A, and 30B are electron micrographs of tabular grain emulsions without icoæitetrahedral protrusions.
Ba~ground of ~h~ Invention Silver halide photography has been practiced for more than a century. The radiation sensitive silver halide compositions initially employed for imaging were termed emulsions, since it was not originally appreciated that a solid phase was present. The term "photographic emulsion" has remained in use, although it has long been known that the radiation sensitive component is present in the form of dispersed microcrystals, typically referred to as grains.
Over the years silver halide grains have been the eubject of intense investigation. Although high iodide silver halide grains, those containing at least 90 mole percent iodide, based on silver, are known and have been suggested for photographic applications, in practice photographic emulsions almost always contain silver halide grains comprised of bromide, chloride, or mixtures of chloride and bromide optionally containing minor amounts of iodide. Up to about 40 mole percent iodide, based on silver, can be accommodated in a silver bromide crystal structure without observation of a separate silver iodide phase. However, in practice silver halide emulsions rarely contain more than about 15 mole percent iodide, with iodide well below 10 mole percent being most common.

1~81'~'~7 All silver halide grains, except high iodide silver halide grains, exhibit cubic crystal lattice ~tructures. However, grains of cubic crystal lattice structures can differ markedly in ~ppearance.
In one form silver halide grains when microscopically observed are cubic in appearance. A
cubic grain 1 is shown in Figure 1. The cubic grain is bounded by six identical crystal faces. In the photographic literature these crystal faces are 10 usually referred to as {100} crystal faces, referring to the Miller index employed for designating crystal faces. While the ~100} crystal face designation is most commonly employed in connection with silver halide grains, these same crystal faces are sometimes also referred to as {200} crystal faces, the difference in designation resulting from a difference in the definition of the basic unit of the crystal structure. Although the cubic crystal shape is readily visually identified in regular grains, in irregular grains cubic crystal faces are not always square. In grains of more complex shapes the presence of cubic crystal faces can be verified by a combination of vi6ual inspection and the 90 angle of intersection formed by adjacent cubic crystal faces.
The practical importance of the {lO0}
crystal faces i8 that they present a unique surface arrangement of silver and halide ions, which in turn influences the grain surface reactions and adsorptions typically encountered in photographic applications.
This unique surface arrangement of ions as theore-tically hypothesized is schematically illustrated by Figure 2, wherein the smaller spheres 2 represent silver ions while the larger spheres 3 designate bromine ions. Although on an enlarged scale, the relative size and position of the silver and bromide ions is accurately represented. When chloride ions 1~31Z;~7 are substituted for bromide ions, the relative arrangement would remain the same, although the chloride ions are smaller than the bromide ionæ. It can be seen that a plurality of parallel rows, indicated by lineæ 4, are present, each formed by alternating silver and bromine ions. In Figure 2 a portion of the next tier of ions lying below the æurface tier is shown to illuætrate their relationship to the surface tier of ions.
In another form silver halide grains when microscopically observed are octahedral in appear-ance. An octahedral grain 5 is shown in Figure 3.
The octahedral grain is bounded by eight identical crystal faceæ. These crystal faces are referred to as ~111} crystal faces. Although the octahedral crystal shape is readily visually identified in regular grains, in irregular grains octahedral crystal faces are not always triangular. In grains of more complex shapes the presence of octahedral crystal faces can be verified by a combination of visual inspection and the 109.5 angle of intersection formed by adjacent octahedral crystal faces.
Ignoring possible ion adsorptions, octahedral crystal faces differ from cubic crystal faces in that the surface tier of ions can be theoretically hypothesized to consist entirely of silver ions or halide ions. Figure 4 i8 a schematic illustration of a {111} crystal face, analogous to Figure 2, wherein the smaller sp~ere~ 2 represent ~ilver ions while the larger spheres 3 designate bromine ions.
Although silver ions are shown at the surface in every available lattice position, it has been suggested that having silver ions in only every other available lattice position in the surface tier of atoms would be more compatible with surface charge neutrality.
Instead of a surface tier of silver ions, the surface . . ..

~ ~ 81~7 tier of ions could alternatively be bromide ions. The tier of ions immediately below the surface silver ions consists of bromide ions.
In comparing Figures 1 and 2 with Figures 3 and 4 it is important to bear in mind that both the cubic and octahedral grains ha~e e~actly the same cubic crystal lattice ~tructure and thus exactly the same internal relationship of silver and halide ions.
The two grains differ only in their surface crystal faces. Note that in the cubic cry~tal face of Figure 2 each surface silver ion lies immediately adjacent five halide ions, whereas in Figure 4 the silver ions at the octahedral crystal faces each lie immediately adjacent only three halide ions.
Much less common than either cubic or octrahedral silver halide grains are rhombic dodecahedral silver halide grains. A rhombic dodecahedral grain 7 is shown in Figure 5. The rhombic dodecahedral grain is bounded by twelve identical crystal faces. These crystal faces are referred to as {110} (or, less commonly in reference to silver halide grains, {220}) crystal faces. Although the rhombic dodecahedral crystal shape is readily vieually identified in regular grains, in irregular grains rhombic dodecahedral crystal faces can vary in shape. In grains of more complex shapes the presence of rhombic dodecahedral crystal faces can be verified by a combination of visual inspection and measurement of the angle of intersection formed by adjacent crystal faces.
Rhombic dodecahedral crystal faces can be theoretically hypothesized to consist of alternate rows of silver ions and halide ions. Figure 6 is a schematic illustration analogous to Figures 2 and 4, wherein it can be seen that the surface tier of ions is formed by repeating pairs of silver and bromide ion A

lX~ 7 parallel rows, indicated by lines 8a and 8b, respectively. In Figure S a portion of the ne~t tier of ions lying below the surface tier is æhown to illustrate their relationship to the surface tier of ions. Note that each surface silver ion lies immediately adjacent four halide ions.
Although photographic silver halide emulsions containing cubic crystal lattice structure grains are known which contain only regular cubic grains, such as the grain shown in Figure 1, regular octahedral grains, such as the grain shown in Figure 3, or, in rare instances, regular rhombic dodecahedral grains, such as the grain shown in Figure 5, in practice many other varied grain shapes are also observed. For example, silver halide grains can be cubo-octa-hedral -that is, formed of a combination of cubic and octahedral crystal faces. This is illustrated in Figure 7, wherein cubo-octahedral grains 9 and 10 are shown along with cubic grain 1 and octahedral grain 5. The cubo-octahedral grains have fourteen crystal faces, six cubic crystal faces and eight octahedral crystal faces. Analogous combinations of cubic and/or octahedral crystal faces and rhombic dodecahedral crystal faces are possible, though rarely encoun-tered. Other grain shapes, such as tabular grains androds, can be attributed to internal crystal irregularities, such as twin planes and ~crew dislocations. In most instances some corner or edge rounding due to solvent action is observed, and in some instances rounding is so pronounced that the grains are described as spherical.
It is known that for cubic crystal lattice structures crystal faces can take any one of seven possible distinct crystallographic forms. However, for cubic crystal lattice structure silver halides only grains having {100} (cubic), {lll}

~`~
~'~

(octahedral), or, rarely, {110} (rhombic dodecahedral) crystal faces, individually or in combination, have been identified.
It is thus apparent that the photographic art ha3 been limited in the crystal faces pre~ented by silver halide grains of cubic crystal lattice structure. As a result the art has been limited in modifying photographic properties to the choice of surface sensitizers and adsorbed addenda that are 10 workable with available crystal faces, in most instances cubic and octahedral crystal faces. This has placed restrictions on the combinations of materials that can be employed for optimum photo-graphic performance or dictated accepting less than optimum performance.

F. C. Phillips, An Int~oduction tQ
CrystallQgraphy, 4th Ed., John Wiley ~ Sons, 1971, is relied upon as authority for the basic precepts and terminology of crystallography herein presented.
James, The Theory of the Photographic Pr~cess, 4th Ed., Macmillan, New York, 1977, pp. 98 through 100, is corroborative of the background of the invention described above. In addition, James at page 98 in reference to silver halide grains states that high Miller index faces are not found.
Berry, "Surface Structure and Reactivity of AgBr Dodecahedra", ~LQ~ogra~hic Scie~ce a~
~gineering, Vol. 19, No. 3, May/June 1975, pp. 171 and 172, illustrates silver bromide emulsions containing {110} crystal faces.
Klein et al, "Formation of Twins of AgBr and AgCl Crystals in Photographic Emulsions", Photogr -phische Korrespondenz, Vol. 99, No. 7, pp. 99-102 (1963) describes a variety of singly and doubly twinned silver halide crystals having {100}

,.

~L~8~ 7 (cubic) and {lll} (octahedral) crystal faces.
Klein et al is of interest in illustrating the variety of shapes which twinned æilver halide grains can assume while still exhibiting only {111} or {100} crystal faces.
A. P. ~. Trivelli and S. E. Sheppard, The Silver Bromide Grain of Photo~raphic Emul~ions, Van Nostrand, Chapters VI and VIII, 1921, is cited for historical interest. Magnifications of 2500X and lower temper the value of these observations. Much higher resolutions of grain features are obtainable with modern electron microscopy.
W. Reinders, ~Studies of Photohalide Crystals~, Kolloid-Zeitschrift, Vol. 9, pp. 10-14 (1911); W. Reinders, ~Study of Photohalides III
Absorption of Dyes, Proteins and Other Organic Compounds in Crystalline Silver Chloride", Zeit~chrift ~ hy~ Li~hQ ~h~i~. Vol. 77, pp. 677-699 (1911~;
Hirata et al, "Crystal Habit of Photographic Emulsion 20 Grains~, 1 Photog. ~Q~. of Japan, Vol. 36, pp.
359-363 (1973); Locker U.S. Patent 4,183,756; and Locker et al U.S. Patent 4,225,666 illustrate teachings of modifying silver halide grain shapes through the presence of various materials present during silver halide grain formation.
~ummary of ~ Inven~LQ~
In one aspect this invention is directed to a silver halide photographic emulsion comprised of radiation sensitive silver halide grains of a cubic crystal lattice structure comprised of icositetra-hedral crystal faces.
In another aspect this invention is directed to a photographic element containing at least one emulsion of the type previously described.
The invention presents to the art for the first time the opportunity to realize the unique 1~:8~X7 _g_ surface configuration of icositetrahedral crystalfaces in photographic silver halide emulsions. The invention thereby renders accessible for the first time a new choice of crystal faces for modifying photographic characteristics and improving interac-tions with sensitizers and adsorbed photographic addenda.
Descri~tion of Preferred Embodiments The present invention relates to silver halide photographic emulsions comprised of radiation sensitive silver halide grains of a cubic crystal lattice structure comprised of icositetrahedral crystal faces and to photographic elements containing these emulsions.
In one form the silver halide grains can take the form of regular icositetrahedra. A regular icositetrahedron 11 ls shown in Figures 8 and 9, which are front and back views of the same regular icositetrahedron. An icositetrahedron has twenty-four identical faces. Al~hou~h any grouping of faces is entirely arbitrary, the icositetrahedron can be visualized as six separate clusters of crystal faces, each cluster containing four separate faces. In Figure 8 faces 12a, 12b, 12c, and 12d can be visualized as members of a first cluster of faces. In Figure 9 faces 13a, 13b, 13c, and 13d can be visualized as members of a second cluster of faces.
The remaining four clusters of faces each have two faces visible in Figure 8 and two faces visible in Figure 9. Faces 14a and 14b, shown in Figure 8, and faces 14c and 14d, shown in Figure 9, represent the four faces of a third cluster of four faces.
Similarly, faces 15a and 15b, shown in Figure 8, and faces 15c and 15d, shown in Figure 9, represent the four faces of a fourth cluster of four faces. Faces 16a and 16b, shown in Fi~ure 8, and faces 16c and 1;~81'~7 15d, shown :Ln Flgure 9, represent the four faces of a fifth cluster of four faces while 16a, 16b, and 16c, shown ln Flgure 8, snd face 16d, shown in Figure 9, complete a ~i.fth cluster of fsce.~ while face.n 17a and 17b, ~ho~n Ln Fi~ure 8, and fsces 17c and 17d, ~hown Ln Figure 9, repre~ent the four faces of a sixth cl.uster of four faces.
Looking at the icositetrahedron it can be seen th~t there Are four intersections of ad~ecent faces wLthin each cluster, and there are two face lntersections of eac}l cluster with each of the four clus~ers ad~&cent to lt for a tot~l of forty-eight face edge .LntersRction3. The relative angles formed by lnte~sect.Lng fRces have only two different values. Al.l i.ntersections of a face from one cluster wlth a face from another cluster sre identical, torming a fJ.rst relatlve angle. Looking at Figure 8, the relative anKle o adjecent fsces 12a and 14a, 12a and 15a, 12b and 15d, 12b and 17a, 12c and 16b, 12c and 17b, 12d snd 16a, and 12d and 14b are all at the Ldent1cal fi.rst relative angl.e. All adJacent face~
within each cluster intersect at the same relative angle, whi.ch is di~ferent from the relative angle of Lntersection of faces in d~fferent clusters. Looking at one cl.uster i.n wh1.ch all faces are fully vl~ible, the .intersecti.ons between faces 12a and 12b, 12b and 12c, 12c and 12d, and 12d and 12a sre all at the same relative angle, referred to as a second relative angle. Whlle the regular icositetrahedron has a distLnct.Lve appearance thst can be recogni~ed by visual lnspecti.on, tt shoul.d be appreciated that measurement of any one of the two relative angles provldeg A corroboratl.on o~ ad~acent hexoctahedral crystal faces.
In crystallography measurement of relative angles ol` adJacent crystal. faces is employed for posLtLve crystal face identification. Such tech-~ 8~ 7 nlques are de~crt.bed, for ex~mple, by Phillips, cited ahove. These technlques can be combined with technlques for the mlcroscoplc examination of silver halide grains to identLfy positively the icositetra-hedral crystQI. faces of ~ilver halide grain~.Technlques for preparing electron micrographs of ~il.ver halide grai.ns are ~enerally well known in the art, as lllustrated by B.M. Spinell and C.F. O~ter, "Photographic Materlals", The EncYcloPedia of MicroscoPv and M~crotechnique, P. Gray, ed., Van No~trand, N.Y., 1973, pp.427-434, note particularly the section dealing with carbon replica electron mlcro~copy on papJes 429 and 430. Employing tech-niques well known J.n el.ectron microscopy, carbon replicas of sllver halide p,rains are flrst prepared~
The carbon replicas reproduce the grain shRpe while avo.idi.ng shape alterlng sl.lver print-out th~t is known to result from empl.oytng the silver halide eralns wlthout carbon shel.ls. An electron scanning beam rather than llght is employed for imaging to permit hlgher ran~es of magnification to be realized than when l:leht ls employed. When the grains sre sufflciently spread apart thst adjacent grains are not lmpi.ngtng, the grai.n~ lie flat on one crystal face rather than on a co1.~n (i.e., a polnt)~ By tLlting the sample being viewed relative to the electron beam a selected grain can be oriented so th~t the l.ine of slght is sub~tantially parallel to both the line of lntersection of two ad~acent crystal faces, seen ~9 a point, and each of the two inter-sectlng crystal faces, seen as edges. When the grain faces are parallel to the i.msging electron beam, the two Go~re~pondine e~ges of the gr~in which they def:lne wlll appeer sharper than when the faces are merely close to belng parallel. Once the deqired graln orlentati.on wlth two intersectlng crystal faces present:lng a parallel edge to the electron be~m is 8~ 7 obt~ined, the angle of intersection can be measured from an electron micro~raph of the oriented grain.
In thls way adJacent lcosl.tetralledral crystal f~ce can be ldentlfi.ed. Relative ~ngles of icositetr~he-S dral and adJacent cryqt~ ces of other Millerindice~ can ~190 be determined in the ssme w~y.
Again, the unique relative angle allow3 a positive ldenttflcati.on of the cryAtal faceq. While relative angle measurements can ~e definitive, in many, if not most, ~nstances vLAual. lnspection of grains by electron microscopy a110ws immediate identification of Lco~itetrshedr~l crystal face~.
ReferrLng to the mutu~lly perpendiculsr x, y, Hnd z axes of a cubLc crystal lattice, it is well recognized ln the art that cubic crystal faces are parallel to two of the axes and intersect the third, thus tSle {100~ MLller lndex ssslgnment; octshe-dral crystal. faces intersect each of the three axes at an equal interv~l, thu~ the {111} Miller index ~ss~nment; and rhom~:i.c dodecahedral crystal faces I.ntersect two of the three sxes at sn equal interv~l and sre parallel to the third axis, thus the {110~ Mlller index ~slgnment. For a given deflnit{on of the baslc cryatal unit, there i8 one and only one Mlller lndex asslgnment for each of cublc, octahedral, and rhomhLc dodecshedral crystal f~ces.
IcosLtetrahedral crystal faces include a family of crystal f~ces that can have differing Miller index values. Ico~itetrahedral cryst~l faces ~re generical.ly des.lgnated as {hQQ} crystal faces, wherein h and Q sre different integers each greater th~n zero and h ls 8re~ter than ~. The regular i.co~Ltetrahedron 11 shown in Figures 8 ~nd 9 consist~ of ~ crystal faces, which corre-sponds to the lowe~t value th~t h and Q can each represent. A regulQr icosLtetrshedron having Z~

{311}, {322}, {411}, {433}, ~511}, {5~}, {533}, or {544} crystal faces would sppe~r simil~r to the lcositetrshedron , ll, but the h:l.gher Mlller indices would result in changes ln the ~ngles of intersection. Although there i9 no theoret.lc~l li.mit on the msximum values of the integers h snd Q, lcositetrshedrsl crystal ~sces havlng 8 v~lue of h of 5 or lesq are more essily genersted. For this ree30n, silver halide grsins hsvlng icos.ttetrahedral crystal fsces of the exemplary Mlller index vslue~ identified sbove sre preferred. Wlth practice one icositetrshedr~l crystal face csn often be distinguished visually from snother of a d:lfferent Mll.ler index value. Measure-ment of relstive sngles permits positive corrobors-tJ.on of the specific Mi.ller index value icositetrahe-dral cryst~l fsces present.
In one form the emulsions of this invention contain sllver hsllde grsins which sre bounded entLrely by icositetrshedrsJ. crystsl fsces, thereby formlng bssicslly ~ep,ulsr lcositetrahedra. In pract).ce slthoueh some edge roundinp, of the grsins is ususlly pre~ent., the unrounded residual flst icosltetrahedral. f.aces permlt pos~tive identifica-tlon, since a sharp intersecting ed8e i9 unnecessary to estsbllshlng the relative angle of ad~scent lcosltetr~hedral. cryst~l. faces. Sighting to orient the gralns is still possible employing the residual flat crystal face portlonq.
The radtation sensitive silver halide grains present ln the emulslons of this invention sre not confined to those ~n whlch the icositetr~hedrsl cryst~l fsce~ sre the only flst crystsl faceq present. Juqt ss cubo-octahedrsl silver halide grslns, such ss 9 and 10, exhibit both cubic snd octahedr~l crystal fsces and 8erry, cited sbove, reports grslns hRvJ.ng cublc, octshedrsl, ~nd rhombic ~28~X'~

dodecahedrsl crystal faces in a single grain, the rsdiation sensitive grains herein contemplated can be formed by icositetrahedrAl crystal faceQ in comb1na-tion with any one or combination of the other types of crystal faces po~sible with a silver halide cubic crystal lattice structure. For example, if conven-tional silver halide grains having cubic, octahedral, and/or rhombic dodecahedral crystal faces are employed as host grains for the preparation of silver halide grains having icositetrahedral crystal faces, stopping silver halide deposition onto the host grains before the original crystal faces have been entirely overgrown by silver halide under conditions favoring icositetrahedral crystal face formation results in both icositetrahedral crystal faces and residual crystal faces corresponding to those of the original host grain being present.
In another variant form deposition of silver halide onto host &rains under conditions which favor icositetrahedral crystal faces can initially result in ruffling of the grain surfaces. Under close examination it has been observed that the ruffles are provided by protrusions from the host grain ~urface.
Protrusions in the form of ridges have been observed, but protrusions, when present, are more typically in the form of pyramids. Pyramids pre~enting ico~ite-trahedral crystal f~ces on host grains initially presenting {lO0} crystal faces have four surface faces~ These correspond to the four faces of any one of the 12, 13, 14, 15, 16, or 17 series clusters described above in connection with the icositetrahe-dron 11. When the host grains initially present ~111) crystal faces, pyramids bounded by three surface faces are formed. Turning to F~gure 8, the apex of the pyramid correspond~2 to the coign formed faces 12b, 15d, and 17a. The protrusions, whether in ~81~;~7 the form of ridges or pyramids, can with~n a short time of initiating precipitation onto the host grains substan~ially cover the original host grain surface.
If silver halide deposition is continued after the S entire grain surface 1~ bounded by icositetrahedral crystal faces, the protrusions become progressively larger snd eventually the grains lose their ruffled appearsnce as they present larger and larger icositetrahedral crystal faces. It is possible to grow a regular icositetrahedron from a ruffled grain by continuing silver halide deposition.
Even when the grains are not ruffled and bounded entirely by icositetrahedral crystal faces, the grains can take overall shapes differing from regular icositetrahedrons. This can result, for example, from irregularities, such as twin planes, present in the host grains prior to growth of the icositetrahedral crystal faces or introduced during growth of the icositetrahedral crystal faces.
The important feature to note is that if any crystal face of a silver halide grain is an icosi-tetrahedral crystal face, the resulting grain presents a unique arrangement of surface silver and halide ions that differs from that presented by all other possible crystal faces for cubic crystal lattice structure silver halides. ThiQ unique surface arrangement of ions as theoretically hypothesized is schematically illustrated by Figure 10, wherein a {211) lcositetrahedral crystal face is shown formed by silver ions 2 and bromide ions 3.
Comparing Figure 10 with Figures 2, 4~ and 6, it is apparent that the surface positioning of silver and bromide ions in each figure is distinctive. The {211} icositetrahedral crystal face presents an ordered, but more varied arrangement of surface silver and bromide ions than is presented at the ~ 2~7 cubic, octahedral, or rhombic dodecahedral silver bromide crystal faces. This is the result of the tiering that occurs at the {211} icositetrahedral crystal fsce. Icositetrahedral crystal faces with differing Miller indices also exhlbit tiering. The differing Miller indices result in analogous, but nevertheless unique urface arrangements of silver snd halide ions. The difference between icositetra-hedral crystal faces of differing Miller indices is illustrated by comparing Figure 10, which is a hypothetical schematic diagram of a {211} crystal face, and Figure 11, which is a corresponding diagram of a {533} crystal face.
While Figures 2, 4, 6, 10, and 11 all contain bromide ions as the sole halide ions, it is appreciated that the same observations as to differences in the crystal faces obtain when each wholly or partially contains chloride ions instead.
Although chloride ions are substantially smaller in effective diameter than bromide ions, an icositetra-hedral crystal surface presented by silver chloride ions would be similar to the corresponding sllver and bromide ion surfaces.
The cubic crystal lattice structure silver halide grains containing icositetrahedral crystal faces can contain minor amounts of iodide ions, similarly ~IS conventional silver halide grai~s.
Iodide ions have an effective diameter substantially larger than that of bromide ions. As is well known in silver h~lide crystallography, this has a somewhat disruptive effect on the order of the crystal structure, which can be accommodated and actually employed photographically to advantage, provided the iodide ions are limited in concentration. Preferably iodide ion concentrstion~ below 15 mole percent and optimally below lO mole percent, based on silver, are 1;~8~7 employed in the practice of this invention. Iodide ion concentrations of up to 40 mole percent, based on silver, can be present in silver bromide cry~tals.
Since iodide ions as the sole halide ion~ in silver halide do not form a cubic crystal lattice structure, their use slone hss no applicability to this invention.
It is appreciated that the larger the proportion of the total silver halide grain surface area accounted for by icositetrahedral crystal faces the more distinctive the silver halide grains become. In most instances the icositetrahedral crystal faces account for at least 50 percent of the total surface area of the silver halide grains.
Where the grains are regular, the icositetrahedral crystal faces can account for all of the flat crystal faces observable, the only remaining grain surfaces being attributable to edge rounding. In other words t silver halide grains having icositetrahedral crystal faces accounting for at least 90 percent of the total grain sur~ace area are contemplated.
It is, however, appreciated that distinctive photogr~phic effects may be realized even when the icositetrahedral crystfll faces are limited in areal extent. For example, where in an emulsion cont~lnlng the silver hal~de grains a photographic addendum is present thut shows a marked adsorption preference for an icositetrahedral crystal face, only a limited percentage of the total grain surface may be required to produce a distinctive photographic effect.
Generally, if any icositetrahedral crystal f~ce is observable on a silver halide grain, it accounts for a sufficient proportion of the total surface area of the silver halide grain to be capable of influencing photographic performance. Stated another way, by the time an icositetrahedral crystal face becomes large 8 ~ ~7 enough to be identified by its relative angle to ad~acent crystal faces, it is already large enough to be capable of influencing photographic perfor~ance.
Thus, the min~mum proportion of total grain surface S area accounted for by icositetrahedrAl crystal faces is limited only by the observer's ability to detect the presence of icositetrahedral crystal faces.
The successful formation of icositetrahedral crystal faces on silver halide grains of a cubic crystal lattice structure depends on identifying silver halide grain growth conditions that retard the surface growth rate on icositetrahedral crystal planes. It is generslly recognized in silver halide crystallography that the predominant crystal faces of a silver halide grain are determined by choosing grain growth conditions that are least f&vorable for the growth of that crystal face. For example, regular cubic silver halide grains, such as grain 1, are produced under grain growth conditions that favor more rapid deposition of silver and halide ions on all other available crystal faces than on the cubic cry~tal faces. Referring to Figure 7, if an octahedral grain, such as regulsr octahedral grain 5 i8 sub~ected to growth under conditions that least favor deposltion of silver and halide ions onto cubic crystal faces, grain 5 during continued silver halide precipitation will progress through the intermediate cubo-octahedral grain forms 9 and 10 before reaching the final cubic grain configuration 1. Once only cubic crystal faces remain, then ~ilver and halide ions deposit isotropically on these surfaces. In other words, the grain shape remains cubic, and the cubic grains merely grow larger as additional silver and halide ions sre precipitated.
By analogy, grains having icositetrahedrsl crystal faces have been prepared by introducing into a silver halide precipit~tion reaction vessel host grains of conventional crystal faces, such as cubic gr~ins, while maintaining growth conditions to favor retarding silver hal~de deposition along lcositetr&-S hedral crystal face~. As silver halide precipitationcontinue~ icositetr~hedral crystal faces first become identifiable and then expand in area until eventual-lyt if precipitation is continued, they account for all of the crystal fsces of the silver halide grains being grown. Since icositetrahedral crystal faces accept additional silver halide deposition at a slow rate, renucleation can occur, creating a second grain population. Precipitation conditions can be ad~usted by techniques generslly known in the art to favor lS either continued grain growth or renucleation.
Failure of the art to observe icositetrahe-dral crystfll faces for silver halide grains over decades of intense inve~tigation as evidenced by published silver halide crystallographic studies suggests that there is not an extensive r~nge of conditions that favor the selective retarding of silver halide deposition slong icositetrahedral crystal faces. It has been discovered that growth modifiers can be employed to retard silver halide deposition ~electively at icositetrahedral crystal faces, thereby producing these ico~itetrahedral crystal faces a5 the external surface~ of the silver halide graLns being formed. The growth modifiers which have been identified are organlc compounds.
They are believed to be effective by reason ~f showing an adsorption preference for a icositetrahe-dral crystal face by reason of its unique arrangement of silver and halide ions. Growth modifiers that have been empirically proven to be effective in producing icositetrahedral crystal faces are described in the examples, below.

These ~rowth modifiers are effective under the conditions of their use in the examples. From empirical screening of a variety of candidate growth modifiers under differing conditions of sllver halide precipitation it has been concluded that mult~ple parameters must be satisfied to achieve lcositetrahe-dral crystal faces, including not only the proper choice of a growth modifier, but also proper choice of other precipitation parameters identified in the examples. Failures to achieve icositetrahedral crystal faces with compounds shown to be effective as growth modifiers for producing icositetrahedral crystal faces have been observed when accompanying conditions for silver halide precipitation have been varied. However, it is appreciated that having demonstrated success in the preparations of silver halide emulsions containing grains with icositetrahe-dral crystal faces, routine empirical studies systematically varying parameterq are likely to lead to additional useful preparation techniques.
Once silver halide grain growth conditions are satisfied that selectively retard silver halide deposition at icositetrahedral crystal faces, continued grsin growth usually results in icositetra-hedral crystal faces appearing on all the grainspresent in the silver halide precipitation reaction vessel. It does not follow, however, that all of the radiation sensitive silver halide grains in the emulsions of the present invention must have icositetrahedral crystal faces. For example, silver halide ~rains having icositetrahedral crystal faces can be blended with any other conventional silver halide grain population to produce the final emulsion. While silver halide emulsions containing any identifiable icositetrahedral crystal face grain surface are considered within the scope of this invention, in most applications the grains having at least one identifiable icositetrahedral crystal face sccount for at least 10 percent of the total grain population and usually these grains will account for greater than 50 percent of the total gre~n population.
The emulsions of this invention can be substituted for conventional emulsions to sstisfy known photographic applications. In addition, the emulsions of this invention can lead to unexpected photographic advantages.
For example, when a growth modifier is pre~ent adsorbed to the icositetrahedral crystal faces of the grains and has a known photographic utility that ~s enhanced by adsorption to a grain surface, either because of the more intimate assoclation with the grain surface or because of the reduced mobility of the growth modifier, improved photographic performance can be expected. The reason for this is that for the growth modifier to produce a icositetrahedral crystal face it must exhibit an adsorption preference for the icositetrahedral crystal face that is greater than that exhibited for any other possible crystal fffce. This can be appreciated by considering growth in the presence of an adsorbed growth modifier of a silver halide graln having both cublc and lco~itetrahedral crystal faces. If the growth modlfier shows an adsorption preference for the icositetrahedral crystal faces over the cubic crystal faces, deposition of silver and halide ions onto the icositetrahedral crystal faces is retarded to a greater extent than along the cubic crystal faces, and grain growth results in the elimination of the cubic crystal faces in favor of icositetrahedral crystal faces. From the foregoing it is apparent that growth modifiers which produce icositetrahedral crystal faces are more tightly ~ 7 adsorbed to these grain surfaces than to other silver halide grain surfaces during grsin growth, and this enhanced sdsorption carries over to the completed emulsion.
To provide an exemplery photographic application, Locker U.S. Patent 3,989,527 describes improving the speed of a photographic element by employing an emulsion containing radiation sensitive silver halide grains having a spectral sensitizing dye adsorbed to the grain surfaces in combination with silver halide grsins free of spectral sensitiz-ing dye having sn average dismeter chosen to maximize light scattering, typically in the 0.15 to 0.8 ~m range. Upon imagewise exposure radlation striking the undyed grains is scsttered rather than being absorbed. This results in an increased amount of exposing radiation striking the radiation sensitive imaging grains having a spectral sensitizing dye adsorbed to their surfaces.
A disadvantage encountered with this approach has been that spectral sensitizing dyes can migrate in the emulsion, so that to some extent the initially undyed grains adsorb spectral sensitizlng dye which has migrated from the initially spectrally sen~itized grains. To the extent that the initially spectrally senaitized grains were optimally sensi-tized, dye migration away from their surfaces reduces sensitization. At the same time, adsorption of dye on the grains intended to scatter imaging radiation reduces their scettering efficiency.
In the examples below it is to be noted that a specific spectral sensitizing dye has been identified as a growth modifier useful in forming ~ilver halide grains having icositetrahedral crystal faces. When radiation sensitive silver halide grains having icositetrahedral crystal faces and a growth ~ 7 modifier spectrsl sensitizing dye adsorbed to the icositetrahedral crystal fsces are substituted for the spectrslly sensitized silver halide grains employed by Locker, the diqadvantageous migration of dye from the icositetrahedral crystal faces to the silver halide grains intended to scstter light is reduced or eliminated. Thus, an improvement in photographic efficiency can be realizPd.
To illustrate another advantageous photo-graphic application, the layer structure of a multicolor photographic element which introduces dye image providing materials, such as couplers, during processing can be simplified. An emulsion intended to record green exposures can be prepared using a growth modifier that is a green spectral sensitizing dye while an emulsion intended to record red exposures can be prepared using a growth modifier that is a red spectral sensitizing dye. Since the growth modifiers are tightly adsorbed to the grains ~nd non-wandering, instead of coating the green and red emulsions in separate color forming layer units, as is conventional practice, the two emulsions can be blended and coated as a single color forming layer unit. The blue recording layer can take any conventional form, and a conventional yellow filter layer can be employed to protect the blended green and red recording emulsions from blue light expo-sure. Except for blending the green and red recording emulsions in a single layer or group of layers di~fering in speed in a single color forming layer unit, the structure and processing of the photographic element is unaltered. If silver chloride emulsions are employed, the approach described above can be extended to blending in a single color forming layer unit blue, green, and red recording emulsions, and the yellow filter layer can ~'~81~;~7 be elimi~ated. The advantage in either case is a reduction in the number of emuls~on layers required AS compared to a corresponding conventional multi-color photogrsphic element.
In more general applications, the substitu-tion of an emulsion according to the invention containing a growth modifier spectral sensitizing dye should produce A more invariant emulsion in term~ of spectral propertles than a corresponding emulsion conta~ning silver halide grains lacking icositetrahe-dral crystal faces. Where the growth modifier is capable of inhibiting fog, such as 2-methyl-5-nitro-l-H-benzimidazole, 2-mercaptoimidazole, or 7-ethoxy-carbonyl-6-methyl-2-methylthio-4-oxo-1,3,3a,7-tetra-azaindene, shown to be effective growth modifiers inthe exsmples, more effective fog inhibition flt lower concentrations may be expected. It is recognized that a variety of photographic effects, such as photographic sensitivity, minimum background density levels, latent imsge stability, nucleation, develop--ability, image tone, absorption, and reflectivity, are influenced by gr~in surface interactions with other components. By employing components, ~uch as peptizers, silver halide solvents, sensitizers or desensitizers, s~persensit$zers, halogen acceptors, dyes, antifoggants, stabilizers, latent image keeping agents, nucleatlng sgents, tone modifiers, develop-ment accelerators or inhibitors, development restrainers, developing agents, and other addenda that are uniquely matched to the icositetrahedrsl crystal surface, distinct advantages in photographic performance over that which can be realized with silver halide grains of differing crystal faces are possible.
~5 The silver halide grains having icositetra-hedral crystal faces can be varied in their proper-~81'~7 ties to satisfy varied known photographic applications as desired. Generally the techniques for producing surface latent image forming grains, internal latent image forming grains, internally fogged grains, surface fogged grains, and blends of differing grains described in Research Disclosure, Vol. 176, December 1978, Item 17643, Section I, can be applied to the preparation of emulsions according to this invention.
Research Disclosur~ is published by Kenneth Mason Publications, Ltd., Emsworth, Hampshire P010 7DD, England. The silver halide grains having hexocta-hedral crystal faces can have silver salt deposits on their surfaces, if desired. Selective site silver salt deposits on host silver halide grains are taught by Maskasky U.S. Patents 4,463,087 and 4,471,050.
The growth modifier used to form the hexoctahedral crystal faces of the silver halide grains can be retained in the emulsion, adsorbed to the grain faces or displaced from the grain faces.
For example, where, as noted above, the growth modifier is also capable of acting as a spectral sensitizing dye or performing some other useful function, it is advantageous to retain the growth modifier in the emulsion. Where the growth modifier is not relied upon to perform an additional useful photographic function, its presence in the emulsion can be reduced or eliminated, i~ desired, once its intended function is performed This approach is advantageous where the growth modifier is at all disadvantageous in the environment of use. The growth modifier can itself be modified by chemical interactions, such as oxidation, hydrolysis, or addition reactions, accomplished with reagents such as bromine water, base, or acid - e.g., nitric, hydrochloric, or sulfuric acid.

Apart from the novel ~r&in ~tructures identi~`ied ahove, the radiat{on ~ensitive silver halide emulsions and the photographic elements in which they are incorporated of thi~ invention csn take any convenient conventional form. The emulsions can be washed a~ described in Re~esrch Disclosure, Item l-/643, cl.ted above, Section II.
The radLatlon sensitlve ~ilver halide grsins of the emul~ions can be surface chemically ~ensi-t.lzed. Noble metal (e.g., gold), middle chalcogen(e.g., sulfur, selenlum, or tel.lurium), and reduction ~ensltlzer~, employed i.ndividually or in combination are speclficall.y contempl.ated. Typical chemical sensitizers are listed in Research Di~closure, Item 17643, clted above, Section III. From comparisons of surface halide and silver ion srran~ements in general the chemical ~ensitIzation response of silver halide RraLns havin~ tcositetrshedral crystal faces should be analogou~, but not identical, to that of cubic and octehedrel ~ilver halide grains. That ob~ervatlon can be extended to emulsion addenda generally which adsorb to 8rain ~urfaces.
The si.lver halide emulsion~ can be qpectral-ly sensitlzed with dyes from fl v~riety of cl~ses, includlnp, the polymethlne dye class, which includes the cysnlnes, merocyanlnes, complex cyanine~ and merocyanlne~ (i.e., tri-, tetra-, and polynuclear cyanl.nes and merocyanines), oxonols, hemioxonols, styryls, merostyryls, and ~treptocyanines. Illustra-tlve spectral sen~itl.zin~ dyes are disclosed in_searc}l _I.sclosure, Item 17643, cited above, Section IV.
The ~.llver halide emulsions AS well as'other layers of the photographic elements of thi~ invention can contain as vehicle~ hydrophilic colloids, employed alone or in combinstion with other polymeric materlals (e.g., latt.ices). Suitable hydrophilic ~.2~3~Z~7 materisls include both natur*lly occurring ubstances such as protelns, protein derivstives, cellulose derlvatives -e.g., cellulose esters, gelstin -e.g., alkali treated gelatin (cattle, bone, or hide eelatin) or acid treated gelatin (pigskin gelatin), gelQtin derivatives -e.g., acetylated gelstin, phth~lated gelatln, and the like, polysaccharides such as dextrsn, gum srablc, zein, ca~ein, pectin, collagen derJ.vatives, collodlon, sgar-sgar, arrow-root, and slbum:l.n. It ls speci.ficslly contemplatedto employ hydrop}ll.llc colloids whi.ch contain a low proportlon dlvalent sulfur atoms. The proportion of divalent sulfur stoms can be reduced by treatin8 the hydrophLl.ic colloid wlth a strong oxidizing agent, such as hydrogen peroxi.de. Among preferred hydrophil.lc col.lolds for u~e as peptizers for the emul.sions of thi.s lnvention sre gelatino-peptizers which contain less than 30 micromoles of methionine per gram. The vehicles can be hardened by conventional procedures. Further details of the vehicles and hardeners are provided in Research Dlsclosure, Item 1764~, cited above, Sections IX and X.
The sil.ver halide photo~raphic elements of thls invention csn contain other sddends conventional in the pht)togrsphic art. Useful addenda are descrJ.bed~ for example, In Research Disclosure, Item 17643, c:lted sbove. Other conventional useful addentia Include antifoggants and stabilizers, couplers (such ss dye forming couplers, masking couplers and DIR coupl.ers) DIR compounds, ant~-stain ~gents, lmage dye stabi.lizers, absorbing materials such as filter dyes and UV absorbers, light scatter-i.ng materlals, antistatic agents, coating sids, snd plasticizers ~nd lubricants.
The photographic elements of the present inventlon can be si.mpl.e black-and-white or monochrome ~a~

elements comprising B support bearing a layer of the silver halide emul~ion, or they csn be multil~yer and/or multicolor element~. The photographic elements produce lmagea r~nging from low contrQRt to very hig}l contra~t, such as those employed for producine half tone imsges ln grsphic arts, They can be de~lgned for proce~Ring with ~epar~te solutions or for in-camera proce~ing. In the latter instRnce the photographLc elemen~s can include conventional imsge tran~fer features, such as those illustrated by Research ~lRclosure, Item 17643, cited sbove, Section XXIII. Multi.color elements contain dye image forming unlts sen~:Ltlve to esch of the three primary regions of the spectrum. Each unit c~n be comprised of ~
single emulslon l~yer or of multiple emulsion layers sensltlve to a gLven re~i.on of the qpectrum. The layers ot' the element, lncl.uding the layers of the imap,e forming units, c~n be arranged in various orders as known in the a~t, In an alternative format, the emulsion or emulsions c~n be dispo~ed as one or more ~eemented layers, e.g., QS by the use of mi.crovessels or microcells, QS de~cribed in Whitmore U.S. Psten~ 4,387,154.
A preferred multicolor photo~r~phic element sccording to this invent10n containing incorporated dye imaRe provldi.ng m~teri.als comprlses a support be~r.lng ~t least one blue sensl.tlve sllver hallde emulsJ.on layer havlne associated therewlth ~ yellow dye formlng coupler, at lea~t one green sensitive sl.lver halLde emul.si.on layer havlng associated therewith a magenta dye formi.ng coupler, and &t least one red sensltlve sllver halide emulslon layer havlng assoclsted therewith a cyan dye forming coupler, at least one of the sllver halide emulsion lsyers contalning grains having icosLtetrahedral crystal faceR as previou~ly described, 8~ 7 The e].e~ents of the present invention can contsin sddltlonal layers conventional in photo-graphic elements, such as overco~t layers, spAcer layers, fllter layers, antihalation layers, and scavenger layers. The support can be any suitable support used wlth photograph~c elements. Typ~cal supports 3.nclude polymerlc films, paper (including polymer-coated paper), glass, and metsl supports.
Details re~srdi.n~ supports and other layers of the photo~raphic elements of this invention are contained in Rese rch Dlsclosure, Item 17643, cited ~bove, Section XVII.
The photoF,raphic elements can be im&gewise exposed wi.th var:Lous forms of energy, which encompass the ultravlolet, vlslble, and infra~ed re~ions of the el.ectromap,netlc spectrum as weJ.l as electron beam and beta rAdlat:lon, gamma ray, X rsy, alpha particle, neutron rsdiati.on, and other forms of corpuscular and wave-like radiant ener~y in either noncoherent (random phase) forms or coherent (in phase) forms, as produced by lasers. When the photographic elements are intended to be exposed by X rays, they can include ~eatures found in conventional radiogr~phic elements, ~uch ~s those illustrated by Research Dlsclosure, Vol 184, Au~ust 1979, Item 18431.
Processing of the imagewise exposed photo~rsphlc el~ments can be ~ccomplished in any convenient conventional manner. Processing proced-ures, developirlg a~ents, and development modifiers sre lllustrated by Research Dlsclosure, Item 17643, cLted ahove, Secti.ons XIX, XX, and XXI, respectively.
ExamPles The :I.nventlon c~n be better appreciated by reference to the foll.owine specific examples. In each of the examples the term "percent" means percent by weJ.F,ht, unless otherwise indicated, and all solutlons, unl.ess otherwise indicated, are aqueous ~'~ 8 solut1Ons. Dllute nitric acid or dilute sodlum hydroxlde was employed for pH ad~ustment, ~9 required.
ExamPle This example illustr~tes the preparation of an icositetrshedral ~5.1.ver bromide emulsion having the Mlller tndex {21.1), beginning with a cubic host emulsion and usLng as erowth modifier Compound I.
~3=~ T - CH2CH
\-=-/ \S--~
c~3 S
Compound I
To a resction vessel. supplied with a stlrrer wss sdded 0.05 mole of a cublc ~ilver bromide emulsl.on of mean p,r~.n size 0.8~m, containing Rbout 10 g/Ag mole of gelstln. Wster was edded to mske the total we:L~ht 50 8- To the emulsi.on st 40C was added 2.0 mill1mole/Ln1tL~l Ae mol.e o~ compound I dissolved in 2 mL. of methanol and 2 drops of triethylamine.
The emuls~.on wss then held for lS min. ~t 40C. The pH was adJusted to 6.0 at 40C. The temperature W8S
rsi.sed to 60C, snd the PAe sdJusted to 8.5 at 60C
wLth KBr and mslntslned st thst value during the preclpttstLon. A 2.5M sol.ution of AgNO~ wa~
lntroduced at a constant rste over R period of 125 mtn. wh.lle a 2.5M sol.utlon of KBr wss sdded 8S needed to ho1.d the pA~ constsnt. A total of 0.0625 mole Ag WQS added.
A csrbon replS.cs el.ectron microgr~ph (Figure 12) shows Emulsion l to have 5.cos~tetrshedral faces.
The Mill.er lndex of the lcosttetrahedral faces was determi.ned by measurement of the relative angle between two sdJacent Lcosltetr~hedral crystal faces.
From th:l.s snp,le, the suppJ.ement of the relstive angle, whlch is the angle between their respective crysta].lographic vectors, ~, coul.d be obtained, ~nd the Mlller index of the sdjscent icositetrshedral ~8~ 7 crystal f~ces was ldentlfied by comparison of this sngle ~ wlth the theoretical intersecting angle between [hlQlQl~ and rh2Q2Q23 vectors. The sngle ~ W8S cslculsted as described by Phlllips, clted above, at psges 218 and 219.
To obtsin the sngle ~, a carbon replics of the crystal qsmple WR4 rotated on the stsge of ~n electron microscope until, for ~ chosen cryst~l, the angle of observation ws4 directly slong the line of intersectLon of the two sd~acent crystal faces of lnterest. An e1ectron mi.crogrsph was then msde, ~nd the relst:lve angle was me~sured on the microgrQph wtth a protr~ctor. The supplement of the measured relstive sngle was the angle ~ between vectors.
Compsrl40n of ~ wlth ~ enabled the crystal fAces to be asslgned. If the experiment~lly determined sngle wa~ nearl.y mid-w~y between two theoretical sngles, the one sssocl.ated wlth the lower Miller ~ndex was used for the assi~nment. The re~ults for Emulslon 1 sre summarized i.n Table I. The number of measurements msde ls given in psrentheses. Theoreti-cal vsl.ues for vectors up to {544} were considered.
ExsmPle 2 Ttli4 example il.lustrAtes the prep~r~tion of sn ico~itetrahedrsl silver bromide emulsion hsving the Mller lndex ~211}, beginning wlth a cubic host emulsion, and usin~ Compound II ss a growth modifier.
H2~ T--Et CH~
Compound II
Th:ls emuls10n was prepared ss described for Exsmple 1, except that the growth modifier w~s 2.0 ~2~7 ml.lllmole/Ag mole of Compound II, dls~olved in 3 mL.
N,N-dlmethylformamlde. The preci.pitstion was carried out for 100 mLn., consumine 0.05 moles Ag. An electron mlcro~raph of the resulting ico~tetrshedral S emulston gralns ~s shown In Figure 13. The Miller Index was determS.ned to be j211} by the me~Qure~
ment~ ted ln ~able I, using the method described for Example l.
ExsmPle 3 Thi.s example Lllustrates the preparation of sn icositetrshedrsl sllver bromide emulsion having the Miller index {211}, beginning with a cubic host emu1.s~on and using 4-hydroxy-6-methyl-2-methyl-mercapto-1,3,3a,/-tetrazaindene (Compound III) a5 a growth modifier.
To a resctlon vessel. supplied with a stirrer wsq sdded 0.4 g of de.lonized bone gelatin dissolved in 24 g o~` water. To thi~ was added 0.04 mole of a cublc si.lver bromlde emuls3.on of mean grain size 0.8~m, containlng 10 e/Ag mole gelatin and having a total weight of 15.7 e. The mixture was heated to 40C, and 6 millLmoles/Ag mole of Compound III were added, dissolved in 3 ml,. water and 3 drops triethyl-amine. The resultlng mtxture was held for 15 min. st 40C. The pl~ wss ad~usted to 6.0 at 40C. The emulsion wa9 then heated to 60C, the pAB sd~usted to 8.S at 60DC with KBr, and maintained at that value durlng the preciplt~ton. A 2M solution of AgN03 was lntroduced over a perlod of 100 min. at a constant rste, whlle a 2M solution of KBr wss added as needed to hold the PAR con~tant. A total of 0.04 mol.e Ag wa~ added.
An elect~on m.l.crograph of the resultin~
Lcositetrahedra1. emulsion gralns is shown in Figure J.4. The Mlller index was determined to be {2111 by v:i.Qus1. comparl~on with an accurate model of a {211} lcositetrshedron.

8 ~ 7 ExamPle 4 Thl~ exsmple .I.I.lust~te~ the prepar~tlon of an Lco~ltetr~hedrsl ai.lver bromIde emulAion hsving the M.Lller index {211~, beglnning with a cubic host emut~ton and u~ing Compoun~ IV as 8 growth modifier.

i~ \[/ \ ~ CH2CH2503H

Compound IV
The emulsLon was prepsred ss de~cribed for Exsmple 1, except thst the growth modifier was 2.0 mllllmole/Ag mol.e of Compound IV, di~solved in 6 mL.
ot` N,N - dimethylformsmlde, 1.5 mL. of wster, ~nd 3 drops of trlethylsmlne. The precipitstion was carried out for 100 mi.n., consuming 0.05 mole Ag.
An electron mlcrogrsph of the re~ultin~
lcosltetrahedrsl emulsion 8rsins is 3hown in Figure lS. The Miller :Index wa~ determined to be ~211~
by the me~urements lI~ted ln Tsble I, using the methods descri.bed for Example 1.
ExamPle 5 Thls example lll.ustrste~ the prepsr~tion of an icosltetrshedral. si.lver bromlde emulsion hsving the Mlller lndex ~211~, beginning with a cubic ho~t emulsion, snd usi.ng Compound V as a growth modifier.
.~ \./S \ ~ -Et I! /'=-\ !

Et Compound V
Emul~ion Exsmple S w~ prepared aq de~cribed for Exsmple 1, except for the following changes: The .~81ZZ7 growth modifier was 2.0 mi.llimole/Ag mole of Compound V, dissolved in 3 ml.. of N,N-dimethylform~mlde. The prec.LpitstLon was carried out usLng 2.OM AgN03 and 2.0M KBr, :In two stages. In the first stage, the AgN03 sol.utl.on w~s sdded over 8 period of 75 min., consumi.ng 0.03 mole Ag. In the second stsge the AgN03 addltlon rate wss hslved, so thRt Rn Rddltional 0.01 mole Ag was added over a period of 50 min. The pAg was maintRined at 8.5 throughout by addi~ion of the KBr solutlon as described for Ex~mple 1.
An electron micrograph of the resulting icositetrRhedral emul.sion gralns is shown in Figure 16. The Mtller ~ndex W8S determined to be {2ll~
by the measurements 11.sted in Table I, using the method described for Example l.
Exsmple 6 Th.Is example illustrates the preparation of an .i.cosltetrshedral sil.ver bromide emul~ion having t}~e Mi3.1er index {21l~, be8inning with ~n octahed~al host emulslon and using 2-methyl-5-nitro-lH-ben~imldazole (Compound VI) as the growth modifier.
The emulsIon was ~repared as described for Example l, except ~or the fol.lowing changes: The host emu].s1.on was 0.05 mole of an oct~hedral silver bromlde emulsion of mean grQl.n slze O.8~m. The growth modifler was 6.0 millimole/initial Ag mole of Compound VI disso1.ved in 3 mL. methanol. The precipitatton was over a period of lOO minutes consuming 0.05 moles Ag.
An electron microgr~ph of the resulting icosltetrahedral emulsion grains is shown in Figure l~. The Miller 1.ndex W8S determined to be ~2ll) by tSIe measurements ].isted in Table I, using the metS1od described for Example l.
Example 7 This example il.lustrates the preparation of an i.cosItetrahedral sllver bromide emulsion having 1'~81'~7 the Miller index {211~, beginning wi~h a cubic ho~t emul.si.on, using a~ growth modifier Compound VII, and wlth ammoni.~ pre~ent durLng the shell precipi-tstion.
0 ,H

H03SCH2--C112~ \C6H5 Compound VlI
To a reactlon ves~el supplled with a stirrer wa~ added 1.0 g of deionlzed bone gelatin dissolved in 27 S g of wster. To this w~s ~dded 0.05 mole of a cubic sllver bromlde emulsion of mesn grsin size 0.8~m, containing sbout 10 g/Ag mole of gelstin snd having A totsl weight of 21.6 8- The emulsion was hested to 40C, snd 2.0 mlllimole/initisl A8 mole of Compound VII were sdded, di~solved in a 2.5 mL.
portion of a 301vent prepsred from 18 mL. N,N-di-methylformamLde, 2 ml. wster ~nd 1 drop of triethyl-~mlne. The mlxture wss hel.d st 40C for 15 min.
Just prior to begi.nning the precipitstion3.'~ mllllmoles of sn AqueOU3 (NH4)2SO4 qolution (1.0 ml.), contslninP~ ~lso 0.25 mlllimoles of KBr, was added, followed hy 25.9 millimoles of ammonlum hydroxlde (~..0 mL). The PAe wss messured ss 9.2 st 40~C, and was ms.Lntsined through the precipi-tst:l.on. At 40C a ~..5M solutlon of AgN03 was sdded st a constsnt flow rste slonp, with 8 2.5M solution of KBr 8~ necesssry to msintsin the pAg. THe precipit~-tion consumed 0.05 mole A~ over 8 period of 100 min.The pH WAS then slowly AdJusted to 5.5.
An electron micro~rsph of the resulting icositetrahedrsl emulsion grains i~ ~hown in Figure 18. The Mil.ler index wa~ determined to be ~211}
by the measurement~ liqted in Tsble I, u~ing the method de~cribed for Exsmple 1.

~;~ 8~

ExamPle 8 This example Lllustrates the preparation of an ico~itetr~hed~al silver bromide emulsion using a cubic host emul~ion ~nd Compound VII 89 growth modifier, as in Example ~, but in the sbsence of ammoni.s durtng the preclpitstion of the outer portion (l.e,, shell) of the grai.ns. The resulting grains showed 8 M.Lller lndex of {311} 8S compared to the {211~ .Lndex of the grains prepared in the presence of ammonia.
To a resctlon ve~sel supplied with Q stirrer wss sdded 0.04 mol.e of a cubic silver bromide emu1.sion of mean graln slze 1.8~m, contsining ~bout lOg/Ag mole gelatin. The emulsion wss diluted with distlJ.led wster to a tota1. weight of 40 grams. KBr solutlon (0.5 ml.) wss sdded to bring the bromide concentrstion of the emulsion tn the resction vessel to 5 x 10 M. The emul.sion W8S heated to 40C, snd l.5 millimoles/Ag mole of Compound VII were sdded, dlsso1ved in 1 mL. of a solvent prepared from l3 mL.
N,N-dimethylformamide, 2 mL. wster, and 2 drops of trlethylamine. The mixture was held for 15 min. at 40C. The pH W8S ad~usted to 6.0 st 40C. The emulsion was then heated to 60C. The pAg was sdJusted to 8.5 at 60C with KBr and msintained at thst v~1ue durlnp, the prec1.pitatlon. A 2M solution of AgN03 wss lntroduced over a period of 123 min.
at a constsnt ~ste, while 8 2M solution of KBr WRS
added as needed to hold the pAg constant. A totsl of 0.02 mole Ag was added.
Two scsnnlng electron microgrsphY of the resultlng icositetrshedr~l emulslon grains are shown in Fi.gures 19A snd l9B. The Miller index was determined to be {311~ by the measurements listed in Tsble I, uslng the method described for Exsmple 1.
_8mP 1 e 9 Thi.s emulsion illustrates the preparstion of sn icositetrahedra1. silver bromide emulsion having the Mil1.er index l311}. beginning with a cubic lloRt emulsion, using Compound VIII R~ the growth mod.Lfier, ~nd w~th ~mmoni~ present during the preclpitstlon of the outer portion of the grain.
Th IQ emu].si.on w~s prepared a3 described for Example 7, but with the followi.ng differences: The deionlzed bone gel~tin w~s omitted from the starting solution. The growth modifler was 3.0 millimole/Ag mole of Compound VIII dl~qolved i.n 3 mL methsnol and 2 drops of triethyl~mine. The pAg prior to the preclp.ltat~.on was messured as 9.4 ~t 40C end ma.i.nt~lned ~t thst vRlue durl.ng the precipitation.
~-\ /O \ ~ CH-co2H
I ll =CH-CH= \S T
~./ \ ~ ~S 3 Compound VIII
An electron m~crogr~ph of the resulting LcositetrQhedr~l emul.qion gr~ins is shown in Figure 20. By visu~1. comp~rison of the mlcrogrsphs with ~n sccur~te model, the Miller index was determined to be {311}.
Example lO
~hls ex~mple i.1.1uQtr~tes the prep~r~tion of ~n lcosltetrshed~l silver bromide emulsion h~ving the Mlller lndex {311}, begi.nning with a cubic host emulslon and using Compound IX ~s the growth modifier.
`? S T

Compound IX
Thls emulsion W8S prepared ~s described for Ex~mple 1, but using 2.0 millimole/A~ mole of Compound IX as ~ growth modifier, dissolved in 3 mL.
N,N-~lmethyl.form~mide. The precipitation time was l00 min., consuming 0.05 mole Ag.
An electron micrograph of the resulting ico~itetrahedral. emu1.sion grains is shown in Figure 21. The Mil.ler index W8S determined to be ~3ll~
by the messurement~ listed in Table I, using the method descr~bed for Example l.
Example ll This emulsion illu~trates the prepsrQtion of silver bromide icositetr~hedral emulsion hAving a {311~ Mll1.er index by the Ostwald ripening of ~
~msll ersl.n slze AgBr emu1.sion onto a mixture of cubic snd octahedrsl host gralns in the presence of Compound X actlng ag a growth modifier.

~C I 5 ~ i/ \ ~ \ -SCH

Compound X
To a reaction vessel were added 32.5 8 (7-5 millimole) of a fre~hly prepsred AgBr Llppmann emul.slon of mean grain size 6pproxim~tely 0.02~m contalnlng 167 g/Ae mole of gelatin. At 35C, 0.09 milJ.imole of Compound X wa9 added, dissolved in l mL
methanol ~nd l mlJ N,N-dtmethylformsmide. Then 3.0 ml., 7.5 ml1.llmo1.e of AgBr consistlng of a m1xture of two emulsLons cont~lning approximately equal numbers 3 ol: cubes (0.8llm mean grain size; l0 gtAg mole ~elat.l.n) snd octahedrs (0.81lm mean grain size; l0 g/A~ mole gelstin) were added. The pH was ~d~usted to 6.0 at 40C, and the pAg to 9.3 with KBr solu-tion. The mlxture was then he~ted to 60C, ~nd ~llowed to stir ~t thst temperature for l9 hrs.
Figure 22 ls an el.ectron micrograph of the resulting emulsion, show.5.ng the cryst~ls to have an 8~Z'~7 icositR~rahedr~l. habit. The Miller index W8S
determined to be ~311] by vi~ual comp~ri~on with an accurate model of a regular {311} ico~i-tetrahedron.
S ExamPle 12 Thl~ example lllustrates the preparation of a ~ilver bromide icositetrahedral emulsion having {533~ Miller index crystal. faces, using a cubic host emul3lon and Compound XI, 2-mercsptoimidazole as 0 8 growth modifier.
The emul.si.on was prepared 85 described for Example l, but using 6.0 mllllmolelAg mole of Compoun~ XI as growth modtfier, dissolved in 3 mL.
methanol. The preclpltatlon time was 100 min., consumlnR O.OS mole Ag.
An electron micrograph of the resulting icosi.tetrahedral emuls:lon grains iq shown in Figure 23. The Miller J.ndex was determined to be ~533}
by the measurement~ llsted in Tsble I, using the method de~cribed for Example 1.
ExamPle 13 This example lllustrate~ the preparation of an icosltetrahedral silver chloride emulsion having {21l~ Mil.ler lndex c~ystal faces, using a cubic si.lver chloride host emulsion and Compound VI as the growth modi.~ier. It is to be noted that the same Mi.ll.er lndex c~ystal faces were obtained when this p~rowth modlfier was used to prepare the silver bromi.de emulsion of Exsmple 6.
To a reaction vessel qupplied with a stirrer wsq added 0.05 mole of a cubic silver chloride emulslon of mean g~ai.n si7e 0.65~m contsining 40 g/Ag mole gelatin. Water was added to make the total weJ.ght 48 g. To the emulsion at 40C were added 6.0 milll.mole/Ag mole of Compound VI dlssolved in 3 mL.
methanol. The emulsion wa~ held 15 min. at 40C.
The temperature was then raised to 50C. The pH w~s adJu~ted to 5.93 at 50~C and m&lntained ~t sbout thi~
value dur.lnK the precipitation. The pAg wa~ ad~usted to 7.7 at 50C wittl NaCl ~olut$on and m~intained at that v~lue dur.l.ng the precipitation. A 2.5M solution S of AgNO3 ws~ Introduced at a constsnt rate over a period of 125 min., whlle a 2.7M ~olution of NaCl was added as needed to hold the pAg constant. A total of 0.0625 mole Ag was added.
An electron micrograph of the resulting ico~itetrahedra1. emulsion grains is shown in Figure 24. The Mll.ler index was determined to be {211}
by the meQsurements ll.~ted ln Table I, using the method descri.bed for Example 1.
ExamPle 14 This example ill.ustrates the preparation of an .Lcosltetrahedral sllver chl.oride emul9ion havin8 the Mlller lndex {522}, making use of Compound I
a9 the g~owth mod:l.f.ler. It Is noted that the use of Compound I ~esulted ~n an index of {211} in the c&se of the ~llver hromide emulsion of ~xample 1.
The emulsi.on was prepared by a procedure simllar to that descrlbed in Example 13, but with the following change~: The 8rowth modifier was 2.0 mllli.moles/Ae mole of Compound I, dissolved in 2 mL.
methanol and 2 drops of trLethylamine. The pH was mai.ntained at 5.92 at 50C, and the pAg was main-ta~ned ~t 7.9 during the precipitation.
An electron mlcrograph of the resulting icositetrAhedral emulsion grains is ~hown in Figure 25. The Mll~.er index was determined to be 1522}
by the measurement3 l~ted in Table I, using the method described for Example 1.
ExamPle 15 Thls example tllustrates the preparation of an lcos1tetr~hedrsl ~ilver bromoi.odide (3 mole I.odi.de~ emulsion havl.ng the Ml.ller index {211~, employLne a cubic ABB~I host emulsion and Compound VI
as growth modifier.

l ~lZ'~7 To a reactlon ve~el supplied with a stirrer was added 0.05 mole (50 B) of a cubic ilver bromoiodlde emulsion, of mean grain 3ize 0.6~m, cont,alnLng 3 mole % lodide and 30g/Ag mole gelatin.
To the emulsion at ~0C were added 6.0 millimole~/Ag mole of Compound VI dissolved in 3 mL. methanol, The emul~lon was held 15 min. at 40C. The temperature was then raised to 60C. The pH was ad~u ted to 6.0 at 60C and malntained at that value. The pAg was adJusted to ~.5 wit,h K~r and maintsined st 8.5 throughout the ~recipitation. A 2.5M solution of AgNO3 W8S Lntroduced at a constant rate over a period of 250 min., while 8 solutlon which was 2.43M
In KBr and 0.0/M in KI W89 sdded as needed to hold the pAg constant. A total of 0.0625 mole Ag was added.
An electron mlcrograph of the resulting Icositetrahedral emul31On 8rain~ i~ shown in Figure 26. The Mlller Lndex W8S determined to be {211}
by visual compsrI30n w~th an accurate model of a reRular {211~ icositetrahedron.
Example 16 This example illustrates the preparation of an icositetrahedral sIlver bromoiodide (3 mole %
lodlde) emu1sion having the Miller index {211~, employlne a cublc Ae8rI host emulsion and Compound I
a9 a growth modifier.
This emu1sLon was prepared by the procedure described for Example 15, but using 3.0 millimoles/Ag mole o~ Compound I as a growth modifier, dissolved in 3 mL. methanol and 3 drops of triethylamine. The pH
was maintained at 5.87 at 60C.
An elect~on micrograph of the resulting icosltetrahedral emul~ion grains is shown in Figure 2/. The Miller Index was determined to be {211}
by comparlson with an sccurate model of a regular {2111 lcositetrahedron.

8~ 7 TABLE I
An~le Measurement Data Type An~le Between Vectors Theoretlc~l ~211~ 33.6 48.2 " {311~ 50.5 35.1 " {322l 19.~ 58.0 " {411) 60.0 27.3 " {433} 13.9 61.9 " {511} ~6.0~ 22.2 ~ {522~ 43 3 40.8 " {533~ 24.9~ 54.5 " {544~ 10.8 64.0 TABLE I (cont'd) AnKle Mes~urement Data 15 Exam~ rowth Angle TY~e ~lide Modl~ier Between Vectors 1 {211} AgB~ I29.2~1.0(3) 51.3+0.8(3) 2 1211} AgBr II33.7~1.3(7) 48.5+0.8(8) 3 {211}* AgBr III

4 {2~} AgBr IV47.4+1.1(5) {211~ A~Br V50.0+1.4(4) 6 {211} ARBr VI31.0~0.8(4) 49.5+2.6(6) / {211~ AgBr VII34.8+1.9(6) 47.2+1.3(9) 8 (3117 ARBr VII48.2+3.5(4) 35.4+1.3(8) 25 9 {3Jl}* AgBr VIII
{311} AgBr IX49.6~0.5(5) 36.0+0.9(8) 11 t3117~ AgBr X - -t2 {s33? AgBr XI24.0+2.0(4) 53.8+1.8(8) 13 {2111 AeCl VI34.8+1.3(4) 47.2+0.9(6) 30 14 {5227 AgCl I45.8+2.7(5) 38.3+2.4(6) {21l7* A~BrI VI
16 {211~* AgBrI
* Determinefl by visual comparison with an sccur~te model of ~ regular icositetrahe~ron of the same Mlller index ExsmPle 17 Thlq example llluqtr~tes addition~l growth modifiers capsble of producing icositetrahedrsl c~y~tal fRces and llsts potential growth modifiers :i.nvestiKat0d, but not obse~ved to produce icositetrs-hedral crystal faces.
The graln growth procedure~ employed were of three different types:
A. The fi.~st grain growth procedure was 8S
follows: To a reactlon vessel supplied with a sti.rrer was added 0.5 g of bone gelatin dissolved in 28.5 g of water. To this was added 0.05 mole of silver bromide host graln emulsion of mean 8rain ~ize 0.8~m, contalning about lOg/Ag mole gelatin, and hav.1.ng a total. wetght of 21.6 g. The emulsion was heated to 40C, ~nd 6.0 millimoles/Ag mole of dissolved growth modifier were sdded. The mixture W8S hel.d for 15 min. at 40C. The pH w~s ad~uqted to 6.0 at 40C. The emulsion wa~ then heated to 60C, and the pAg was ad~usted to 8.5 at 60C with KBr and maintained at th~t value during the precipi-tst.lon. The pH, which shifted to 5.92 at 60C, was held At th~t value thereafter. A 2.5M solution of AaNO3 and a 2.5M solution of KBr were then introduced w.lth 8 constant sll.ver addition rate over a perlod of 125 min., consumtne 0.0625 mole Ag.
B. The second grain growth procedure was as followq: To 8 reaction vessel supplied with a stlrrer wes added 27.5 mL of water. To this was add~d 0.05 mole of a si.lver bromide host grain emulslon of mean graln size 0.8 ~m, containing about 10 g/Ag mole of gel~tin and having a totsl weight o~ 21.6 g. The emulsion was heated to 40C, and 3.0 mil~.imole/initial Ag mole of dis~olved growth modifter was added. The mixture wa~ held at 40C for 15 mi.n. Just prlor to beginninB the precipitation 3.4 mll.limoles of an a~ueous (NH4)2SO4 ~olution :

8~ ~7 (1.0 mL), contslning ~lso 0.25 millimole of KBr, w~s ~dded, followed by 25.9 mill.imoles of smmonium hydroxlde (2.0 ml.). The pAg was messured as 9.3 st 40C and was mal.ntalned ~t that level throughout the precipLtatlon. At ~0C a 2.5M solution of AgN03 was added at R constsnt flow r~te Rlon~ with ~ 2.5M
so1.ution of KBr, the latter being added at the rate necesssry to ma.lntaln the pAg. The preclpit~tion con~umed 0.05 mole Ae over 8 perlod of lO0 min. The pH wa~ then ~lowly ad~u~ted to 5.5.
In the first snd second procedures cubic or octshedral host graIns were employed hS noted in Table I. Smsl1. samples of emulsion were withdrawn st intervsls durlnp, the precipitation for electron mlcroscope examination, sny tetrAhexAhedrsl crystal faces revealed ln such ssmp1.es are reported in Tsble I.
C. The third grain growth procedure employed 7.5 mi.111moles of ~ freshly prepared very fine graln (approxJ.mately 0.02 ~m) A8Br emulsion to which was added 0.09 mllll.mo1.e of growth modifier.
In this process the~e very fine AgBr grains were d:lssolved and repreclpitated onto the host grains.
The host grsln emulsion contsined 0.8 ~m AgBr grains. A 7.5 mill.lmole porti.on o~ the host grain emu1.slon W~9 ~dded to the very eine grRln emulsion.
pH of 6.0 snd pAg of 9.3 st 40 C was employed.
The mlxture was stirred st 60 C for sbout 19 hours.
The crysts1. fsces presented by the host grslns are as noted i.n Table I. Where both octahe-drsl and cubic host erains are! noted using the same growth mod.lfier, a mixture of 5.0 millimoles cubic gralns of 0.8 llm and 2.5 millimoles of octahedral grglns of 0.3 llm wss employed giving approximately the same number of cublc and octahedral host grsins.
In looki.ng st the grsi.ns produced by ripening, those produced by ripening onto the cubic grsins were 8~2'~7 resdlly visua11y dl~tinguished, since they were 1arger. Thus, it was pos31b1e in one ripen1ng process to determine the cryst~1 faces produced using both cubic and octahedra1 host grain~.
Differences 1.n i.ndtvidual procedure~ ~re lndlcated by footnote. The {hQQ~ surface column of Tsb1e II refers to those surface~ which sstisfy the def:l.nltion above for icositetr~hedr~1 crysts1 faces.

.

1.2~ 7 T A B L E II
lhQ~ Host Growth Modifier Surfaces Grains Method 1 5-Nitro-o-phenyl-eneguanidine nitrate None cublc C
2 Citrlc acid, tri-sodium salt None cubic C
3 5-Nitroindazole None cubic C
None oct~hedral C
4 1-Phenyl-5-mercap-totetrazoleNone octahedrsl (1)(2) A

5 5-Bromo-1,2,3-ben- None cubic A
zotriazole None octahedral C

6 6-Chloro-4-nitro-1,2,3-benzo- None cubic C
triazole None octahedral C

7 5-Chloro-1,2,3-ben- None cubic C
zotriazole None octahedral C

8 5-Chloro-6-nitro-1,Z,3-benzo-triazole None cub~c C

9 3-Methyl-1,3-benzo-thla.zolium ~-toluene3ul- None cubic C
fonate None oct~hedral C

10 4-Hydroxy-6--methyl-1,3,3a,7-tetra-azaindene, sodlum salt None octahedral C

11 4-Hydroxy-6-methyl-2-methylmercapto-1,3,3a,7-tetra-azaindene 1211} cubic A

~81~27 T A B L E II (continued) {hQQ) Host Growth Modifier Surfaces Grains Method 12 2,6,8-Trichloro- None cubic C
purine None octahedral C

13 2-Mercapto-l-phenyl- None cubic C
benzimidazole None octahedral C

14 3,6-Dimethyl-4-hy-droxy-1,2,3a,7- None cubic C
tetraazaindene None octahedral C

15 5-Csrboxy-4-hydroxy-1,3,3s,7-tetra- None cubic C
azaindene None octahedral C

16 5-Cflrbethoxy-4-hy-droxy-1,3,3a,7-tetraazaindene None cubic A

17 5-Imlno-3-thiour- None cubic C
azole None octahedral C

18 2-Formamidinothio-methyl-4-hydroxy-6-methyl-1,3,3a,7- None cubic C
tetraazaindene None octahedral C

19 4-~ydroxy-2-B-hy-droxyethyl-6-methyl-1,3,3a,7- None cubic C
tetraazaindene None octahedral C

20 6-Methyl-4-phenyl-mercapto 1,3,3a,7- None cubic C
tetraazaindene None octahedral C
30 21 2-Mercapto-5-phenyl- None cubic C
1,3,4-oxadiazole None octahedral C
22 l,10-Dithia-4,7,13,16-tetra- None cubic C
oxacyclooctadecane None octahedral C
23 2-Mercapto-1,3- None cublc C
benzothiazole None octahedral C
24 6-Nitrobenzimidazole None cubic (3) A

~X8~2Z'7 T A B L E II ~continued) {hQQ} Host Growth ModifierSurfsce~ Grains Method 25 5-Methyl-1,2,3- None cubic C
benzotriazoleNone octahedral C
26 Vrazole None cubic C
None octahedral C
27 4,5-Dicarboxy-1,2,3-triazole,None cubic C
monopotassium salt None octahedral C
28 3-Mercapto-1,2,4- None cubic C
triazole None octahedral C
29 2-Mercapto-1,3- None cubic C
benzoxazole None octahedral C
6,7-Dihydro-4-methyl-6-oxo-1,3,3a,7-tetra-None cubic C
azaindene None oct&hedral C
31 1,8-Dihydroxy-3,6- None cubic C
dithiaoctane None octahedral C
32 5-Ethyl-5-methyl-4-thiohydantoinNone cubic A
33 EthylenethioureaNone cubic A
None octahedral A
25 34 2-Carboxy-4-hydroXY-6-met;hyl-1,3,3a,7-~ None cublc C
tetraazaindeneNone octahedral C
35 Dithi.ourazole None cubic C
None octahedral C
36 2-Mercaptoimidazole {533} cubic A
37 5-Carbethoxy-3-(3-carboxypropyl)-4-methyl-4-thia- None cubic C
zoline-2-thioneNone octahedral C
38 Dithiourazole-methyl vinyl None cubic C
ketone monoadduct None octahedral C

28~ 7 T A B L E II (continued) {hQ~} Host Growth Modifier Surface~ Gr~ins Method 39 1,3,4-Thiadiazoli- None cubic C
5dine-2,5-dithione None octahedral C
40 4-Carboxymethyl-4-thiazoline- None cublc C
2-thione None octahedr~l C
41 1-Phenyl-5-selenol-tetrszole, octahedral pota~sium salt None (1)(2) A
42 1-Carboxymethyl-5H-4-thiocyclopenta- None octahedral C
(d~uracil None cubic C
43 5-Bromo-4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene None cubic A
44 2-Carboxymethyl-thio-4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene None cubic C
45 1-(3-Acetamido-phenyl)-5-mercap-totetrazole, ~odium salt None octahedral C
46 5-Carboxy-6-hydroxy-4-methyl-2-methyl-thio--1,3,3a,7-tetraazaindene None octahedral C
47 5-Carboxy-4-hy-droxy-6-methyl-2-methylthio-1,3,3a,7-tetraazaindene None cubic A
35 48 -Thiocaprolactam None cubic (1) A

~2 8~7 T A B L E II (continued) {hQQ} Ho~t Growth Modifier Surfsces Grains Method 49 4-Hydroxy-2-methyl-thio-1,3,3a,7-tetraszaindene None cubic A
50 4-Hydroxy-2,6-di-methyl-1,3,3a,7- octahedral tetraazsindene None ~4) A
10 51 Pyridine-2-thiol None octahedral (8) A
52 4-Hydroxy-6-methyl-1,2,3a,7-tetrs- octahedral azaindene None (4) A
15 53 7-Ethoxycarbonyl-6-methyl-2-meth-ylthio-4-oxo-1,3,3a,7-tetra-azaindene 1311} cubic C
54 1-(4-Nitrophenyl) -5- octahedral mercaptotetrazole None (1)(2) A
55 4-Hydroxy-1,3,3a,7- octahedral tetraazaindene None (4) A
56 2-Methyl-5-nitro-lH-benz:lmidazole {211} octahedral A
57 Benzenethiol None octahedral (1)(8) A
58 Melamine None cubic C
None octahedral C
3059 1-(3-Nitrophenyl)-5- None cubic C
mercaptotetrazole None octahedral C
60 Pyridine-4-thiol None octahedral (1) A
61 4-Hydroxy-6-methyl-3-methylthio-1,2,3a,7-tetra-azaindene None cubic A

8~ 7 T A B L E II (continued3 {hQQ} Host Growth Modi~ierSurfaces Grains Method 62 4-Methoxy-6-methyl-1,3,3a,7-tetra-az~indene None octahedral A
63 4-Amino-6-methyl-1,3,3a,7-tetr~
azaindene None octahedral A
64 4-Methoxy-6-methyl-2-methylthio-1,3,3a,7-tetra-azaindene None cubic A
65 4-Hydroxy-6-methyl-1,2,3,3a,7-penta-azaindene None octahedral A
66 3-Carboxymethyl-rhodanine None cubic (1) A
67 lH-Benzimidazole None octahedral A
68 4-Nitro-lH-benz-imidazole None octshedral A
69 3-Ethyl-5-[(3-ethyl-2-benzoxszolinyli-dene)ethylidene]-4-phenyl-2-thioxo-3-thlazoliniumNone cubic C
iodicle None octahedral C

30 i ll \ =CH-CH= / ~ Ie / \N/ \S/ ~S
Et lX~

T A B L E II (continued) {hQQ} Host Growth Modlfier Sur~aces Grains Method 70 3-Ethyl-5-(4-methyl-2-thioxo-3-thia-zolin-5-ylidene- None cubic C
methyl)rhod~nine None oct~hedr~l C
0 Me Et- ~ S/

71 3-I~opropyl-[~3-ethyl-2-benzothi~-zolidinylidene)-ethylidene]rho-dsnine None cubic B
o I~ il ~ =CH-CH=-/ ~ -C

Et 72 3,3'-D:Lethylthia-cyanine P-tolllene sulfonate None cubic (5) A

I il ~ -CH=-/ Ij ~1 Et Et pts9 73 3-Ethyl-5-(3-ethyl-2-benzothi~zolin-ylidene)rhodanine {211} cubic (5) A
o S ll .~ \./ \ / \~-Et ~-/ \N/ \S/ ~S

Et ~ 7 T A B L E II (continued) {hQQ} Host Growth ModifierSurfaces Grains Method 74 3-Ethyl-5-(3-ethyl-2-benzothiazo-linylidene)-2-thio-2,4-oxazoli-dinedione None cubic (5) A
o îf \il/S\.=. / ~ -Et Et 15 75 5-(3-Ethyl-2-benzo-thiazollnylidene)--1,3-diphenyl-2- None cubic C
thiohydantoin None octahedr~l C
o i~/il/\N/-=-~

Et 25 76 3-Ethyl-5-(3-ethyl-2-benzoxazollnyl-idene)rhodanine None cublc (5) A
o I~ 'D' \.=./ ~ - Et La~ 7 ~54~
T A B L E II (continued) ~hQQ~ Host Growth Modifier Surfaces Grains Method 77 3-Methyl-4-[~1,3,3-trimethyl-l(H~-2-indolylidene)-ethylidene]-l-phenyl-2-pyrazo- None cubic C
lin-5-one None octahedral C

Me Me 78 5-(1,3-Dithiolan-2-ylidene)-3-ethyl--rhodanine 1322} cubic (5) A
o ~2 1 \.=~/ ~ Et 79 5-(5-Methyl-3-pro-pyl-2-thiazolinyl-idene)-3-propyl-rhodanine {311} cubic (5) A

o M~./ \ / \y- CH2-CH2-Me ~ \ S/ ~S
C~H2 C~H2 Me T A B L E II (continued) .
{hQQ} Host Growth Modifier Surfaces Gr~ins Method 80 3-Carboxymethyl-5-[(3-ethyl-2-benz-oxazolinylidene)-ethylidene]rhoda- None cubic C
nine None octahedral C
o 10 o ii t~ / \ =cH_cH=~/ Y CH2 C 2 ~ / \N/ \S/ ~S
Et 15 81 5-(3-Ethyl-2-benzo-thi~zolinylidene)-3-B-sulfoethyl-rhodanine {211~ cubic (5) A
o Et 82 5-Anllinomethylene-3-(2-sulfoethyl)-rhodanine {311~ cubic (6) A
O

30 HS03-CH2-CH2- ~ \ =CH-S~ \S

T A B L E II ~continued) {h~Q} Host Growth ModifierSurface~ Grains Method 83 3~ Carboxyethyl)-5-[(3-ethyl-2-benzox~zolinyli-dene3ethylidene]-rhodanine {311} cubic B
o 0 ll CH-Me I ll ~ =CH-CH=-\ ~ C02H

Et 5 84 3-(1-Carboxyethyl)-5-[(3-ethyl-2-ben-zothiazolinyli-dene)ethylidene]-rhodanine None cubic B

.~ \./S\ /l! ~ CH-Me !~ I! ~ =CH CH \ /.~ C02H

Et 3-(3-C~lrboxypropyl)-5-[(3-ethyl-2-ben--zoxazol~nylidene)-ethylidene]rhoda-nine Yeq cubic B
o ~ ,o l!
T il . =CH-CH=./ Y CH2-CH2-CH2-CO2H
~/\~ \S/~S

Et ~81~27 T A B L E II (continued) {hQQ} Host Growth ModifierSurfaces Gr~ins Method 86 3-(2-Carboxyethyl)-5-[(3-ethyl-2-ben-zothiazolinyli-dene)ethylidene]- None cublc C
rhodanine None octahedr~l C
o t~ \./ \ / \~ -CH -CH C0 H
I! ,-=CH-CH=-~ 2 2 2 / W ~S/ ~S
Et 87 3-Csrboxymekhyl-5-[(3-methyl-2-thia-zolidinylidene)-isopropylidene]-rhodanine None cubic B
O

~~ H22-1 ~ =CH-C-. \ ~ CHZCO2H

Me 88 3-C~rboxymethyl-5-[(3-methyl-2-thi-azolidinylidene)-ethylidene]rhoda- ~
nine None cubic B
o S
H2--' \ -CH CH- / ~ CH2C2 H-! - - _.

Me T A B L E II (continued) {hQQ} Host Growth ModifierSurfaces Grain~ Method 89 3-Carboxymethyl-5-{[3-(2-carboxy-ethyl)-2 th~azoli-dinylidene]ethyl-idene~rhodanineNone cubic B
o H2_i ~ =CH-CH=- / ~- CH2C2H

( CH2 ) 2C02H
3-(-Carboxy-benzyl)-5-[(3-ethyl-2-benzoxazo-linylidene)ethyl-idene]rhodanine None cubic B
O

t 11 =CH-CH=-/ ~-CHC02H
~ / \~ \S/ ~S
I

Et 91 3-(-Carboxyben-zyl)--5-[(3-methyl-2-thiazolidinyli-dene)ethylidene]-rhodanine None cubic B
O q>

HH2_1 ~ =CH-C=- / ~ CHC02H

Me . , -5~ -T A B L E _ II (continued) ~hQQ} Host Growth Modifier Surf~ces Grains Method 92 1-Ethyl-4-(1-ethyl-4-pyridinylidene~-3-phenyl-2-thio- None cubic C
hydantoin None octahedr~l C
o o Et--N/ \.=. / \~--Et \ N/ ~S

93 Anhydro-3-ethyl-9-methyl-3'-(3-sul-fobutyl)-thia-carbocyanlne None cubic C
hydroxide None octahedral C
Me ~ ll +\ -CH=C-CH=./ It t / \ ~ \ N/ \.
Et cHH22 Me 94 3-Ethyl-5-[1-(4-sul-fobutyl)-4-pyri-dinylidene]rhoda-nine, piperidine ~one cubic C
~alt None octahedral C
o 3 2 4 N~ _ / \ / -I + I
H~ ~H

8~ ~7 T a B L E II (continued) {hQQ} Host Growth Modifier Surfaces Grains Method 95 5-(3-Ethyl-2-benzo-5thiazolinylidene)-l-methoxycarbonyl-methyl-3-phenyl- None cubic 2-thiohydantoin None octahedral C
o 10 ~Ss\5~

Et CH2 C=O

96 1,1',3,3'-Tetraeth-ylimidazo(4,5-b)-quinoxalinocar-bocyanine ~-tolu-enesulfonateNone cubic B
Et Et N \ ~ \ 4 t il i =CH-CH=CH - + ~
25 ~./ \ ~ \ ~ ~ ~N/ \-f Et pt~Et 97 3-(2-Carboxyethyl)-5-(1-ethyl~4-pyridinylidene)- cubic rhodanine ~311} (1)(2) A
o Et- ~ CH2-cH2co2H

T A B L E II (continued) {hQ~] Host Growth ModifierSurfaces Grains Method 98 3-Carboxymethyl-5-{[3-(3-sulfopro-pyl)-2-thiazoli-dinylidene]ethyl-idene}rhoda-nine, sodium salt None cubic (1) A
o Il H2-l\ ~ =CH-CH=./ ~ _CH2-C02H

(CH2)3Soe Na+
99 3--(1-Carboxyethyl)-5-{[3-(3-s~lfo-propyl)-2-thiazol-idinylidene]ethyl-idene~rhoda-nine, ~odium salt None cubic B
1l CH3 H2_i ~ =CH-CH=.~ ; ~- CH-co2H

e (CH2)3S03 Na T A B L E II (continued) {hQQ} Host Growth ModifierSurfaces Grains Method 100 3-(3-C~rboxypropyl)-5-{[3-(3- ulfo-propyl)-2-thiazol-idinylidene}ethyl-idene}rhoda-nine, sodium selt None cubic l7) A
o Il H2_i\ ~ =CH-CH= \ ; ~ CH2)3C2H

(CH2)3S0~ Na 101 3-(2-Carboxyethyl)-5-~[3-(3-~ulfo--propyl)-2-thi~zol-idinylidene~ethyl-idene}rhoda- None cubic C
nine, sodium salt None octahedral C
o s l!
H2-i =CH-CH=./ ~- CH2-CH2C02H
2 \N/ \ S/ ~S
(CH2)31503 Na ~281~7 T A B L E II (continued~
{hQQ} Host Growth ModifierSurfaces Grains Method 102 3-Carboxymethyl-5-(2-pyrrolino-1-cyclopenten-l-yl-methylene)rhoda-nine, sodium salt {211} octahedral A

~ \ =CH- I~ \
15 103 3-Ethyl-5-(3-methyl-2-thiazolidinyli-dene)rhodanine {2111 cubic (5) A

o H2-j/ \ _./ \~- Et H - /

Me 104 5-(4-Sulfophenyl-azo)--2-thiobarbi-turic acid, None cubic C
sodium salt None octahedral C
o o3S--f ~.-N=N-./ \yH
N + ~ S
a H

~X81~27 T A B L E II ~continued) {hQQ} Host Growth Modifler Surfaces_ Gra~ns Method 105 3-Carboxymethyl-5-(2,6-dimethyl-4(H)-pyran-4-yli-dene)rhodanine {211} cubic (5) A
o 10 ~< \, = . / \~1--CH2 C02H

106 Anhydro-1,3'-bis(3-~ulfopropyl)naph-tho[l,2-d]-thia-zolothiacyanine hydroxide, tri-ethylamine salt None cubic (5) A

(CH2)3 S03~ S03e HNEt3 107 3-Ethyl-5-[3-(3-sul-fopropyl)-2-benzo-thiazolinylidene]-rhodanine, trieth-ylemine salt {211} cubic (5) A

~ /S\ / ~ _ Et ~-/ \N/ \S/ ~S
(CH2)3 SOe HNEt3 T A B L E II (continued) ~hQQ} Host Growth Modifi.er Surf~ces Gr~ins Method 108 3-Ethyl-5-[3-(3-sul-fopropyl)-2-benz-oxazolinylidene]-rhodanlne, potss- None cubic C
slum salt None octahedral C
o T~ \tl/ \.=./ \9J-- Et ~ / ~ \S/ ~S
(CH2)3S33 K+

(l) 3 mmoles of growth modifier/Ag mole of host gr~i.n emulsion was employed (2) a pBr of 1.6 was employed (3) 9 mmoles of erowth modifier/Ag mole of ho~t g~fiin emulsi.on was employed, added in two portions (4) 50C was emp].oyed ir.stead of 60~C
(5) 2 mmoles of growth modifier/Ag mole of host eraln emulsion was employed (6) l.5 mmole~ of growth modifier/Ag mole of host grain emulsion was employed (/) 4 mmol.es of growth modifier/A~ mole of host ~rstn emulsion was employed (8) a p~r of 2.3 w~s employed ComP~rstive Example 18 The purpose of thi~ comparative example is to report, the result of sdding 6-nitrobenzimid~zole to a re~ction vessel prior to the precipit~tion of ~i.lver bromide, as su~eested by Wulff et al U.S.
Patent l,696,830.
A rescti.on vessel. equipped with a 3tirr~r waa charged wlth 0,75 g of delonized bone ~elatin made up to 50 ~ wi.th water. 6-Nttrobenzimid~zole, z~

16.2 mg (0.3 wei~ht % hased on the Ag used), di3solved in lmL of methanol, wa~ sdded, followed by 0.055 mole of KBr. At 70~C 0.05 mole of a 2M
sol.ution o~ A~NO3 wa~ added at ~ uniform rate over 5 8 period of 25 mi.n. The grai.ns formed were relative-ly thi.ck tabtets 3howing {111} crystal fsces.
There was no indicati.on of the novel icositetrahedral crystsl faces of the invention.
Comparative Example 19 The purpo~e of this comparative example i5 to report the result of employing 4-hydroxy-6-methyl-1,3,3a,7-tetr~azai.ndene, sodium salt during grain precipitati.on, as suggested by Smith Particle Growth and SusPension, clted above.
To 100 mL of a 3% bone gelatin solution were added sl.mul.taneousl.y 10 mL of 1.96 M AgNO3 and lOmL
of 1..96 M KBr at 50DC with stirring over a period of about 20 sec. The A~r di.spersion was aged for 1 min at 50C, then dl1.uted to 500 mL. The dispersion was ad~usted to p~r 3 with KBr.
_amples 19a and l9b.
To 80mL of lX10 M KBr containing 0.4 mmole/Q of 4-hydroxy-6-methyl-1,3,3a,7-tetraaza-~.ndene, sodi.um salt and 0.6 mmole/Q of l-dodecyl-qui.nol.ini.um bromide was ~dded 20 mL of the ~bovedtsper~ion, whi.ch was then stirred at 23~C. Samples were removed ~fter 15 min (Sample l9a) and 60 min (Sample l9b).
SamPles l9c and l9d SQmples 19c and l9d were prepared similarly as Samples 19a and 19b, respectively, except that 0.8 mmole/Q of 4-hydroxy-6-methyl-1,3,3a,7-tetrQazain-dene and 0.6 mmol.e/Q of l-dodecylquinolinium bromide were used.
~xaml.nation of the grains of each of thP
samples revealed rounded cublc grains. No icosi-tetrsheArsl. crysta1. faces were observed.

lX~ 27 Exam2le 20 Emulsi.on ~xample 20 illu~trates the preparation of ~ ruffled tsbul.ar grsin silver bromide emulsion us1.ng ~9 a growth modlfler Compound 81, 5-~3-ethyl-2-benzothi.azolinylidene)-3-~-sulfo-ethyl rhodanl.ne, which is known to be useful as a blue spectral sensitizing dye.
To a reactlon vessel suppl~ed with a stirrer was added 0.04 mole of a thln and high aspect ratio tsbular grain AB~r emul.~ion of mean grain 3ize 5.6 ~m, thicknes~ 0.10 ~m containin~ about 20 g/Ag moJ.e gelati.n. Water was ~dded to make the total we.i.ght 40 g. To the emul.sion at 40~C was sdded 4 mill.i.mole/i.nl.tial. Ae mole of Compound 81 dissolved in 7mL of N,N-dimethy1.formam5.de, 3mL water, and 2 drops of triethy~.amlne. The emulsion was then held for 15 min at 40C. The pH was sd~usted to 6.0 at 40C.
The temperature W8S raised to 60C, snd the pAg ad~u~ted to 8.5 at 60C with KBr and msintained at that value during the preci.pitation. A 2.OM solution of AgN03 was introduced at a constant rste over a pe~lod of 2.0 min whi.le a ~M soluti.on of KBr was &dded es needed to hold the pA~ constant. A total of 0.02 mole Ag wss added.
An electron ml.crograph of the resulting emulsion grain~ i.s shown in F.tgure 28. The grsin faces were uni.forml.y covered with closely arranged, sharp, small pyrami.dal ruffles. This was consi~tent w.l.th the [2.11~ icositetrahedral cry~tal faces expected from i.nvesti.~ation of the same growth modi.fier empl.oyin~ a nontabular host grain emulsion.
Example 21 Example 21. illustrates the preparation of ruffled tabulsr ~rain silver bromoiodide emulsions us1.n~ Compound 81 a~ the growth modifier. Example 21A i.s a control showing that no ruffles are formed i.f t;he growth modi.fier is added following, rather than preceding, the silYer halide precipitat~on on the host emulslon.
To a reaction ves~el ~upplied with 8 gtirrer WAS added 0.05 mole of a thin and high aspect ratio tabul&r grain sllver bromoiodide emul~ion (6 mole I) of mean 8rain size 5.3 ~m, thickness 0.07 ~m, and containi.ng about 40 g/Ag mole gelatin. Water was added to make the total weight 50 g. To the emulsion at 40C prepared accordinp, to the lnvention was added Compound 81 d5.ssolved i.n 12mL of N,N'-dimethyl-formamlde-water-triethylQmJ.ne mixture similar to that de~cri.bed i.n the previous example. In the control the introducti.on of Compound 81 was delayed until after preci.pitation. The emulsion was then held for 15 mtn. at 40~C. The pH was ad~usted to 6.0 at 40C. The temperature was raised to 60C, and the pAg ad~usted to 8.5 at 60~C with KBr and maintained at that vsl.ue during the precipitation. A 2.OM
so~.ution of AF~N03 was i.ntroduced at a constant rste over a peri.od of 74 mi.n. while a ~olution that was 1.88M J.n KBr and 0.12M i.n KI was added a9 needed to hold the pA~ constant. A total of 0.015 mole Ag W8S
added. The deta5.1s of the three experiments are shown in Table III.
TABLE III
Exam~l.e 21 PreclPitatlons Cpd. 81 Figure mmole/
Example No Ap~ mole Comments 21A 29A 3.0 Control - Cpd. 81 added after precipitation 21.B 29B 3.0 Invention 21C 29C 4.5 Invention Fi.gures 29A, B, and C show electron mJ.crogr~phs of the resultin~ grAins. In Example 21A, aAdlti.on of the growth modi.fier after the precipita-ti.on resulted .Ln no growth of ruffle~ on the host emulsion grslns. Ex~mple 21B, with the same amount of growth modi.fi.er added prior to the precipitstion, produced uniform, closely ~rrsnged, smsll ruffles.
Exsmple 21C, with a hi.gher level of growth modifier, produced a si.mllsr re~ul.t, but with slightly better defined ruffles (pyrsmids).
Measurement was msde of the interf~cisl snele o 8 ruffle on an electron micrograph of ExPmple 6C l.n order to determine the crystsllogr~phic form. The ~ngle between the f~ce vectors w~s found to be 35. The theoreticsl. sngle between [211]
vectorq i.s 33.6. The form wss therefore {211}
I.cosltetrshedral. Thi.s is consistent with other observsti.ons of {211~ icositetrshedrs being formed st~rtl.ng wlth nontsbul~r host grsins ~nd employi.ng Compound 81 as a growth modifier.
Example 22 Example 22 sgai.n illustrstes the preparation of ruffled tabul.sr grsin silver bromoiodide emulsions using Compound 81 (Exsmpl.e 20) a5 the growth mod:l.fler, but shows the dependence of the result on the level of growth modifier added.
The host emulqion (0.05 mole for esch expe~Lment) snd the precipltsti.on conditions were 8S
descrlbed ln Example 21.. The detsils oE the experiments sre shown in Tsble IV.
TABLE IV
ExamPle 22 PreciPit~tions Flgure Cpd. 81 30Exame~e No mmolelA~ mole 22~ 30B 0.75 .2C 30C 1.5 22D 30D 3.0 Figures 30A, B, C, and D are electron microgrsphs of the resultlng emulsion grains.
Exsmple 22A, wlthout growth modifier, ~nd 22B, with 0.75 ml.llimol.e/Ag mole, showed no ruffles. At 1.5 mil.limole, relati.vely large truncated pyrsm~ds sppeared, ~s ~hown in Figure 30C. At 3.0 millimoles Example 22D producPd uni.form, closely srranged, small ruffJ.es. The pyramidsl cry~tal fsce3 were consistent wlth the ~211} cryst~l faces expected from u~ing Compound 81 as ~ growth modifi.er in the previou3 examples.
ExsmPle 23 Example 23 .I.llustrates the preparation of ruffled cubi.c sllver bromide grsln~ using Compound 36, 2-merc~pto.i.mi.dszole, ss e growth modifier.
Cont.Lnued erowth results I.n icositetrahedr~l gr~ins.
To a reaction vessel supplied with a stirrer was sdded 0.05 mole of 8 cubic regular gr~in silver bromide emul.sion of mesn grsin flize 0.8~m, contsining about 10 ~/Ag mole gelatin. Water was sdded to make the total weight 50 g. To the emulsion st 40C wss sdded :3.0 mil.li.moletAg mole of Compound 36 ~J.ssolved in 3mL methanol. The emulsion was then hel.d for 15 m~n at 40C. The pH was sd~usted to 6.0 st 40~C. The tempersture was rsised to 60C, snd the pAg ~dJusted to R.5 st 60C with KBr snd maintsined st thst value durin~ the precipit~tion. A 2.5M
~olution of AgNO3 wss ~dded ~t a constsnt rate over a per:lod of ~5 min whi.le ~ ~.SM solution of KBr wss added ss needed to hold ~he pAg constAnt~ A totsl of 0.0125 mol.e Ae, WQS sdded to form Ex~mple 23A. For Ex~mple 23~ the preci.pltatlon wss continued for a total of 1~5 ml.n, using a total of 0.0875 mole Ag.
An sddltlon~l 3 mi.].l.imole/i.nitial Ag mole of Compound 36 wss ~dded sfter lO0 min of precipitation time.
Fl~ures 31A snd 31~ ~re electron microgr~phs of the resulting emulslon grsins produced by Examples 23A and 23~, respecti.vely. Figure 31A shows 8 p~ttern of growths covering the crystal fsces.
Fi.gure 31~ .illustrstes the formstion of ~533}

1~ 8~ 7 ico3itetr~hedral Rra.ins with continued precipltation.
Example 24 Thi.~ example i.llustr~te~ the modificstion of a growth modtfter ad~orbed to lcositetr~hedral grain 5 gurfaces~
The emul~lon empl.oyed was a ~ilver bromo-iodlde (6 mole percent iodi.de) emulsion containing .J.cositetrahedral grains, the emulsion being prepared by a procedure ~imi.1ar to that of Example 9, except t,hat the host emul.slon was a 0.7~m silver bromo-lod:ide (6 mole percent, i.odlde) ootahedral grain emulslon and the over~rowth ~hase consisted of silver hromolodi.de (6 mole percent iodide) obtained by havinp, an app~opriate amount of NaI in the NaBr salt sol.utlon. The amount of overerowth precipitated was 3.13 times the number of moles of host emulsion used.
The resultlnR icositetrahedrfll 8rain emulsion had 8 pink color due to the adsorption of Compound VIII, a dye employed as the growth modifier, ont,o the gra.i.n's surfaces. The addition of bromine water resulted i.n the complete disappearance of the pink color, lndi.cating destruction of the dye, leaving a yellow color havlng a slight brownish tlnt. The yellow color i9 that expected for AgIBr and the brownish tlnt ts attributed to the reaction products formed i.n destroylng Compound VIII.
Example_25 Thi.s examp~.e illustrates the preparation of an i.cosltetrahedrst silver bromide emulsion having the Mlller lndex {211), beglnning wlth an octahedral core emulslon, and using Compound 102 from Tahle II ag a erowth modl.fi.er. This example further lllustrfltes that the growth modifier can be rendered tnactive hy treatment wtth bromtne water, and a new spectral sensttizing dye can then be used.
The emulsl.on for this example W8~ prepared a9 described for Example 1, except for the following 1~81~Z~

changes: The erowth modifler W89 2eO millimol2~Ag mole of Compound ].0~, di~solved in 8 mL methanol, 5 drops triethylami.ne and 8 ml. distilled water. The starting emulsLon was 0.4 mole of a O.7 ~m ARBr oct~hedrsl emul.si.on containing 16g of gelatin and a total volume of 400g. The AgN03 solution WRS ~dded at a constant rate for 140 min, resulting in 0.70 moles of addit.Lonal AgBr being precipitated. The NaBr sol.ution was twlce as concentrated (5.0M) as the AgN03 solutlon and was added as needed to hold the pAg constant.
Carbon repl.lca electron micrographs showed that well formed {~].1} i.cosi.tetrahedra resulted.
The resultinR emuls:lon W8Q divided in half.
Portlon A. Thls hslf was gently centrifuged and the solld portion resuspended in 300g of 3.7 bone gelRtin solution.
Porti.on B. To this half at 40C, bromine wster was slowl.y added with good stirring until the pink color caused by the adsorbed growth modifier had di.sappeared as determi.ned by dissolving small samples ~nd exami.nl.ng them in white llght. Note: 42g of broml.ne water had been added in 13 min. After the pink color had di~appeared, an additional lOg of bromine water wss slowly sdded. The resulting emu1.slon was gentl.y centrlfuged and the solid AgBr phase WflS resuspended in 300g of 3.7% bone gelatin solution.
Porti.ons A and B were further trested as I.lsted below and costed on acet~te ~upport at 1.08 g Ag/m , 4~31R hone Rel.sti.n/m , and 0.81 g/m of a d:LAper~lon o~ the coupler 2 benzamido-5-[2-(4-butane~ulfonyl.am~dophenoxy)tetradecanamido]-4-chlorophenol, 0.1'~ saponi.n/m as ~preading agent, and 1.8mg hls(vinylQulfonyl.methyl)ether/g gelstin as hardener.

~ ~ 81~7 Emulsion ~. Portion A
2 Port.i.on A + 0.26 mmole/mole Dye A
3 Portion A heated 15 min at 70C with 1.2 mg/mole sodt.um thlosulfate and 0.4 mglmole potassium chloroaurate 4 Portion B + 0.26 mmole/mole Dye A
Portion ~ heated 15 min at 70~C with 3,6 mg/mole so~ium thiosulfate and 1.2 mg~mole potassium chloroaurste 6 Portton B heated 15 min at 70C with 3,6 mg/mole sodium th~.osulfste and 1.2 mg/mole potassium chl.oroaurate + 0.26 mmole/mole Dye A
Dye A ls fl red spectral sensitt.zing dye having the formula:
~ -\ /s\ /s~
!~ U ~ --C~--cl--CH~,i!~ i!

(CH2)3S03 (CH2)3S03 Anhydro-5,5'-dichloro-9-ethyl-3,3'-di(3-sulfo-propyL)thiacar~ocyan3.ne hydroxide, sodium salt These coati.np,s were exposed to a regulated light source whl.ch progressively increased in wavel.enet,h i.n one dlrection and progressively i.ncreased i.n denslty i.n a second direction normsl to t,he fl.rst~ The coati.ngs were then processed in the Kodak C-41~ Color Negative Process (with develop-ment for 3 mi.n 15 9 at 38C) which formed a cyant.maRe showing the s~ectral response of each coating.
Thls l.mage was scanned by a densitometer, and corrected for var:t.sble lamp energy to produce the t,races of constant lma~,e density shown in Figures 32A
and 32B. In Flgure 32A the curves 1, 2, and 4 lndt.cste results for the correspondingly numbered coatln~s, whi.ch were not chemically sensitized, ~..X81~7 Sim.Llarly, ln F~gure 32~ the curves 3, 5, and 6 i.ndl.cate results for the correspondingly numbered coatings, where were chemically sensitized.
By comp&ring curves 1 and 2 in Figure 32A it 5 can be seen that the addLtion of red sensitizing dye A 3.ncreased the sensitivity of the emulsion somewhat, but did not functi.on to shLft the spectral response of the emulsi.on. This is because growth modifier Compound 102, whlch i9 itself a green ~pectral sens3.tlzlng dye, WQ~ already sdsorbed to the icositetrahedrRl grAin surfaces. Curve 4 shows the spectral. re~ponse obtained when the green spectrsl sensLtizlng dye, Compound 102, is destroyed as 8 dye prlor to addl.tlon of Dye A. As can be seen from curve 4, the emuls3.on exhibits no measursble senslt:lvlty ~.n the 470 to 510 nm region of the spectrum, but exhi.hLts a marked increase in spectral sensl.tJ.vi.:lty heyond 650 nm. The curves demonstrate that the spectral. sen~lti.vity lmparted by the growth modlf~er can be destroyed to 8110w spectral senqiti-zatlon of the icositetrahedral emulsions according to the inventlon to a differing portlon of the visible spectrum, if desired.
Looki.ne at Figure 32B, it can be seen from curve 3 that the chemically sensitized icositetra-hedral. emuls3.on exhi.bi.ts measurable ~ensitivity out to about 650 nm aq i.nLti.ally prepared. Sensitivlty ln the 8reen portion of the spectrum is attributable to the green senslti.zation provided by the growth modi.fier, Compound 102. Curve 5 shows the native sensltJ.v:lty remaLni.ng when the spectral sensitizatiLon provided by Compound 102 is destroyed by treating the emulsion wJ.th bromine water. Curve 6 shows the response obtai.ned when the red spectral sensitizing dye, Dye A, i.s thereafter added to the emulsion.
Cumulati.vely Flgure 32A and 32~ show the spectral sensiti.zat.l.on et`fect~ to be achievable independently of chemJ.cal sens3.tlzat3.on of the emulsions.

~ 8~ 7 ExamPle 26 Thls example i.l].ustrates the selective site ep.l.taxlsl depos:Ltlon of 8 silveF salt onto icosi-tetrshedral. gralns of an emulsion sstisfying the requirement~ of thi~ invention.
To a ~eaction vessel supplied with a stirrer was added 0.~ mole of & 0.7~m sllver bromoiodide (6 mole percent i.odide) octahedral emulsion containing ~8g bone gelst~.n/Ag mole. Distilled water W8~
sdded so that the contentR of the kettle weighed 400g. The emulsi.on wsR heated to 40C, and 6.0 mmol.es/Ag mole of 2-methyl-5-nitro-lH-benzimidazole dLssolved in 25ml of methanol was added. The mixture W8S held for 15 mln st 40~C. The pH was sd~usted to lS 6.0 st 60C snd the pAg sd~usted to 8.5 st 60C and mslntalned st these vslueR durtng the precipitation.
A 2.5M solutJ.on of A~NO3 was added &t a constant rate over a psrl.od of 200 mLn consuming Q.5 moles of Ag. Concurrently, a ~oluti.on of 4.95M in NsBr snd 0.3M ln NsI was added st e rste necessary to msintsin a constant pA~ of 8.5 st 60C. The resulting emul.slon wss centri.fuged and the solid silver halide phsse wss resuspended Ln 200ml of 3% bone ~elatin solution. C~rbon replic& electron microgrsphs showed this emulsion to consist of well formed ico~i-tetrshedrs.
Two epl.tsxlal emulsions were prepared. One w~ made ln the presence of the epitaxial qite director, Compound I, the other wss not.

i ~ 81~ 7 ompound I

~cH-c-c~l-. ~ ll ll CH~C~l2CH-CH3 CH2CH2CH-CH3 S03Na S03 Anhydro-9-ethyl-5,5'-diphenyl-3,3'-dJ.(3-sulfobutyl)oxacarbocyanine hydroxlde, monosodium salt To p~epare Emu1Aion A, to a reaction ve~el supplied with 8 st.l.rrer was added 0.05 mole of the a~ove irosLtetrahedrsl host emulsion. Distilled water was added to mske a totsl contents weight of SOg. The contents were heated to 40~C &nd 0.92 mmole of NaCl W8s sdded. An 0.50M solution of AgN03 and R 0. 52M soluti.on of NsCl was then introduced with a const~nt ~l1ver Rddition rate over a period of 10 min, con~umine 2.5 mmol.e of sLlver. During the precLpltation, the pAg was hel.d con~tsnt at 7.5 and the temperature held con~tant at 40C.
To prepare Emulsi.on B, a qimilar procedure was loll.owed 8S ln the precipitat3.on of Emul~ion A, but wLth the followln~, excepti.ons: Before the start of the AgC:l preclpi.tQtlon, 0.64 mmole of Compound I
(&9 ~hown a~ove)/host A~ mole .l.n 2 ml methsnol was Qdded.
Both Emul~i.on A and Emulsion B showed discrete epLtaxial deposits. In the ca~e of Emulsion B, wh3.ch was preci.p3.t~ted 3.n the presence of the site d.l.rector, the cubic {100~ crystal fsces on the ep3.taxy were quite dl.~tinct. Thls exsmple demon-strates that no addLtional site director, ~uch as Compound I, i.s es~enti.al to achieving selective site ep3.taxy, hut ~n adsorbed site director can be Advantaeeous in achi.ev.Lng better definition of cry~tal faces.

~ 7 ExamPle 27 This example i.llustrates 3elected site ep~taxy on ~n i.cositetrahedrsl host emul~lon.
The host emulsion for ~,hi~ example wa.~ that emp~.oyed i`or Example 25. To a reaction vessel supplled with a st.l.rrer was added 0~05 mole of the host emulslon, 0.52 mmole l,l'-diethyl-2,2'-cyanine p-toluenesulfonate i.n 2ml of methanol and distilled water to make a totsl wei.ght of contents of 50g, The contents were heated to 40C and 0.92 mmole of NaCl was added. A O.~OM so].ut1.on of AgNo3 and a 0.52M
soluti.on of NaCl. were then introduced with a constant siJ.ver addi.ti.on rate over a period of lO min consumlng 2,5 mmoles of sil.ver. During the precipi-tation, the pAg wa~ held constant at 7.5, and thetempersture held constant at 40~C.
A 20,000X carbon replica electron micrograph of the resulti.ng emu].sion which has discrete epitaxl~l. growths alonQ the edges ~oining coigns formed by the 5.ntersections of four crystal faces, but no epitaxy along the edBes intersecting st coigns formed by t,he intersecti.ons of three crystal faces.
Thus, there were three well defined, mutually perpendicular rlnes of epltaxy around each icosi-tetr~hedral grain.
The .Invention has heen described in detailwith partlcular reference to preferred embodiments thereof, but i.t wll.l be understood th~t variations and modi.flcations can be effected within the splrit and scope of the invention.

Claims (11)

1. A silver halide photographic emulsion comprised of radiation sensitive silver halide grains of a cubic crystal lattice structure comprised of icositetrahedral crystal faces.

2. A silver halide photographic emulsion according to claim 1 wherein said silver halide grains comprised of icositetrahedral crystal faces are silver bromide grains.

3. A silver halide photographic emulsion according to claim 1 wherein said silver halide grains comprised of icositetrahedral crystal faces are silver chloride grains.

4. A silver halide photographic emulsion according to claim 1 wherein said silver halide grains comprised of icositetrahedral crystal faces contain at least one of bromide and chloride ions and optionally contain a minor proportion of iodide ions based on total silver.

5. A silver halide photographic emulsion according to claim 1 wherein said silver halide grains are additionally comprised of at least one of cubic and octahedrel crystal faces.

6. A silver halide photographic emulsion according claim 1 wherein said silver halide grains are regular icositetrahedral grains

7. A silver halide photographic emulsion according to claim 1 wherein a grain growth modifier is adsorbed to said icositetrahedral crystal faces.

8. A silver halide photographic emulsion according to claim 1 wherein said icositetrahedral crystal faces satisfy the Miller index assignment {h??}, wherein h and ? are integers greater than zero, h is greater than ?, and h is no greater than 5.

9. A silver halide photographic emulsion according to claim 8 wherein said icositetrahedral crystal faces exhibit a {211}, {311}, {322}, {522}, or {533} Miller index.

10. A silver halide photographic emulsion according to claim 9 wherein a grain growth modifier is present in said emulsion chosen from the class consisting of a 4-hydroxy-6-methyl-1,3,3a,7-tetra-azaindene, sodium salt; 2-mercaptoimidazole;
4-hydroxy-6-methyl-2-methylmercapto-1,3,3a,7-tetra-azaindene; 7-ethoxycarbonyl-6-methyl-2-methylthio-4-oxo-1,3,3a,7-tetraazaindene; 2-methyl-5-nitro-1-H-benzimidazole; 3-ethyl-5-(3-ethyl-2-benzothiazolin-ytidene)rhodanine; 5-(1,3-dithiolan-2-ylidene)-3-ethylrhodanine; 5-(3-ethyl-2-benzothiazolinylidene)-3-.beta.-sulfoethylrhodanine; 5-anilinomethylene-3-(2-sulfoethyl)rhodanine; 3-(1-carboxyethyl)-5-[(3-ethyl-2-benzoxazolinylidene)ethylidene]rhodanine;
3-(3-carboxypropyl)-5-[(3-ethyl-2-benzoxazolinyli-dene)ethylidene]rhodanine; 3-(2-carboxyethyl)-5-(1-ethyl-4-pyridinylidene)rhodanine; 3-carboxymethyl-5-(2-pyrrolino-1-cyclopenten-1-ylmethylene) rhodanine, sodium salt; 3-ethyl-5-(3-methyl-2-thi-azolidinylidene)rhodanine; 3-carboxymethyl-5-(2,6-di-methyl-4(H)-pyran4-ylidene)rhodanine; 5-(5-methyl-3-propyl-2-thiazolanylidene)-3-propylrhodanine, and 3-ethyl-5-[3-(3-sulfopropyl)2-benzothiazolinylidene]-rhodanine, triethylamine salt.

11. A photographic element containing an emulsion according to claim 1.