CA1281226C - Emulsions and photographic elements containing silver halide grains having tetrahexahedral crystal faces - Google Patents

Abstract

EMULSIONS AND PHOTOGRAPHIC ELEMENTS CONTAINING SILVER
HALIDE GRAINS HAVING TETRAHEXAHEDRAL 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 tetrahexahedral crystal faces.

Description

EMULSIONS AND PHOTOGRAPHIC ELEMENTS CONTAINING SILVER
HALIDE GRAINS HAVING TETRAHEXAHEDRAL CRYSTAL FACES
Field of the _v ntion 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 Descri~tion of thQ Drawin~s Figure 1 is an isometric view of a regular cubic silver halide grain;
Figure 2 is a schematic 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 regular 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 ~ilver halide grain, and intermediate cubo-octahedral silver halide grains.
Figures 8 and 9 are front and rear isometric views of a regular {210} tetrahexahedron;
Figures lO and 11 are schematic diagrams of the atomic arrangement at silver bromide tetrahexa-hedral crystal surfaces having Miller indices of {210} and {410}, respectively; and Figures 12 through 17 are electron 35 micrographs of tetrahexahedral silver halide grains.
Background of thQ Inventi_n Silver halide photography has been practiced for more than a century. The radiation sensitive r~
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-2-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 subject 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 20 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.
All silver halide grains, except high iodide silver halide grains, exhibit cubic crystal lattice structures. However, grains of cubic crystal lattice structures can differ markedly in appearance.
In one form silver halide grains when microscopically observed are cubic in appearance. A
cubic grain l is shown in Figure 1. The cubic grain is bounded by six identical crystal faces. In the photographic literature these c:rystal faces are 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 ~81~6

-3-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 visual inspection and the 90 angle of intersection formed by adjacent cubic crystal faces.
The practical importance of the {100}
crystal faces is 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 theoreti-cally 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 are substituted for bromide ions, the relative arrangement would remain the same, although the chloride ions are smaller than the bromide ions. It can be seen that a plurality of parallel rows, indicated by lines 4, axe present, each formed by alternating silver and bromine ions. In Figure 2 a portion of the next tier of ions lying below the - surface tier is shown to illustrate 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 faces. These crystal faces are referred to ~.

1~8~2;~6 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 is a schematic illustration of a {111} crystal face, analogous to Figure 2, wherein the smaller spheres 2 represent silver 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 tier of ions could alternatively be bromide ions. The tier of ions immediately below the surface silver ions consists of bromide ions.
~ n comparing Figures 1 and 2 with Figures 3 and 4 it i9 important to bear in mind that both the cubic and octahedral grains have exactly the same cubic crystal lattice structure 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 crystal 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.

,'~1 Much less common than either cubic or octahedral 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 visually 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 parallel rows, indicated by lines 8a and 8b, respectively. In Figure 6 a portion of the next tier of ions lying below the surface tier is shown 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-~'~ 8~ 6 octahedral- 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 screw 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 can take any one of seven possible distinct crystallographic forms. However, for cubic crystal lattice structure silver halides only grains having {100} (cubic), {111} (octahedral), or, rarely, {110} (rhombic dodecahedral) crystal faces, individually or in combination, have been identified.
It is thus apparent that the photographic art has been limited in the crystal faces presented 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 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.

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2f~6 Relevant Art F. C. Phillips, An Introduction to Crystallography, 4th Ed., John Wiley & Sons, 1971, is relied upon as authority for the basic precepts and terminology of crystallography herein presented.
James, The Theo~y of the Photographic Process, 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, I'Surface Structure and Reactivity of AgBr Dodecahedra", hotographic ~ ence and ~ ~g, 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", Photo-graphische Korrespondenz, Vol. 99, No. 7, pp. 99-102 (1963) describes a variety of singly and doubly twinned silver halide crystals having {100}
(cubic) and {111} (octahedral) crystal faces.
Klein et al is of interest in illustrating the variety of shapes which twinned silver halide grains can assume while still exhibiting only {111} or {100} crystal faces.
A. P. H. Trivelli and S. E. Sheppard, ~he~
Silve~ BrQm;ldQ 1a.i~ .Qf _ho~ogra~kic E~siQns, 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-Ze_tschrift, Vol. 9, pp. 10-14 (1911); W. Reinders, "Study of Photohalides III
Absorption of Dyes, Proteins and Other Organic Compounds in Crystalline Silver Chloride", Zeitschrift fur Physikalische Chemie, Vol. 77, pp. 677-699 ~1911);
Hirata et al, ~'Crystal Habit of Photographic ~mulsion Grains", J. Photog. ~. of laE~an. 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.
Summary of thQ Inven~on 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 tetrahexahedral 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 surface configuration of tetrahexahedral crystal faces in photo~raphic sil~er 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.
~e~riptio~ ~f. P~Qf~ mbQd~me~s The present invention relates to silver halide photographic emulsions comprised of radiation sensitive silver halide grains of a cubic crystal lattice structure comprised of tetrahexahedral crystal faces and to photographic elements containing these emulsions.
In one form the silver halide grains can take the form of regular tetrahexahedra. A regular s~

tetrahe~ahedron ll is shown in Figures 8 and 9, which sre front and back views of the same regular tetrahexahedron. A tetrahexahedron has twenty-four identical faces. Although any grouping of faces is entirely arbitrary, the tetrahexahedron 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. A
second clu~ter of faces is represented by faces 13a, 13b, and 13c. The fourth face of the cluster, 13d, is shown 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, 16b, and 16c, shown in Figure 8, and face 16d, shown in Figure 9, complete a fifth cluster of faces. Faces 17a, 17b, 17c, and 17d in Figure 9 complete the sixth cluster of faces.
Looking at the tetrahexahedron it can be seen that there are four intersections of adjacent faces within each cluster, and there is one face intersection of each cluster with each of the four clusters ad~acent to it for a total of thirty-six face edge lntersections. The relative angles formed by interseting faces have only two different values. All intersections of a face from one cluster with a face from another cluster are identical, forming a first relative angle. Looking at Figure 8, the relative angle of ad~acent faces 12a and 14a, 12b and 13b, 12c and 15a, and 12d and 16d are all at the identical first relative angle. All ad~acent faces within each cluster intersect at the same relative angle, which is different from the relative angle of intersection of faces in different clusters. Looking ~,2~ 6 ~t one cluster in which all faces are fully visible, the intersections between faces 12a and 12b, 12b and 12c, 12c and 12d, and 12d and 12a are all at the same relat~ve angle, referred to as a second relative angle. While the regular tetrahexahedron hes a distinctive appearance that can be recognized by v~su81 inspection, it should be appreciated thst me~surement of any one of the two relstive angles provides 8 corroboration of adjacent tetrahexahedral crystsl feces.
In crystallography measurement of relative angles of ad~acent crystal faces is employed for positive crystal face identification. Such tech-niques are described, for example, by Phillips, cited above. These techniques can be combined with techniques for the microscopic examination of silver halide grains to identify positively the tetrahexahe-dral crystal faces of silver hslide grains.
Techniques for preparing electron micrographs of silver halide grains are generally well known in the art, as illustrated by B.M. Splnell and C.F. Oster, "Photographic Materiels", The EncYcloPedis of Microsc~pY and Microtechnique, P. Gray, ed., Van Nostrand, N.Y., 1973, pp.427-434, note particularly the section dealing with carbon replicfl electron micro~copy on pages 429 ~nd 430. Employing tech-niques well known in electron microscopy, carbon replicas of silver halide grains are first prepared.
The carbon replicas reproduce the grain shape while avoiding shape altering silver print-out that is known to result from employing the silver halide grains without carbon shells. An electron scanning beam rather than light is employed for imaging to permit higher ranges of magnification to be realized than when light is employed. When the grains are sufficiently spread apart that ad~acent grains are not impinging, the grains lie flat on one crystsl X8~ v ~6 face rather than on a coign (i.e., a point). By tilting the sample being viewed relative to the electron beam a selected grain can be oriented so that the line of sight is substantially parallel to both the line of intersection of two ad~acent crystal faces, seen as a point, and each of the two inter-secting crystal faces, seen as edges. W~en the grain faces are parallel to the imaging electron beam, the two corresponding edges of the grain which they define will appear sharper than when the faces are merely close to being parsllel. Once the desired grain orientation with two intersecting crystal faces presenting a parallel edge to the electron beam is obtained, the angle of intersection can be measured from an electron micrograph of the oriented grain.
In this way ad~acent tetrahexahedral crystal faces can be identified. Relative angles of tetrshexahe-dral and ad~acent crystal faces of other Miller indices can also be determined in the same way.
Again, the unique relative angle allows a positive identification of the crystal faces. While relative angle measurements can be definitive, in many, if not most, instances visual inspection of grains by electron microscopy allows immediate identification of tetrahexahedral crystal faces.
Referring to the mutually perpendicular x, y, and z axes of a cubic crystal lattice, it i3 well recognized in the art that cubic crystal faces are parallel to two of the axes and intersect the third, thus the {100} Miller index assignment; octahe-dral crystal faces intersect each of the three axes at an equal interval, thus the ~111} Miller index assignment; and rhombic dodecahedral crystal faces intersect two of the three axes at an equal interval and are parallel to the third axis, thus the {110} Miller index assignment. For a given definition of the basic crystal unit, there is one ~8~ 6 snd only one Miller index Rsslgnment for e~ch of cubic, octahedral, and rhombic dodecahedral crystal fsces.
Tetrahexahedral cryst~l faces include a family of crystal faces that can have differing Miller index values. Tetrahexahedral crystal faces are generically designated as {hkO} crystal faces, wherein h and k are different integers e~ch greater th~n 0, which is zero and not to be confused with the letter 0. The regular tetrahexahedron 11 shown in Figures 8 and 9 consists of {2103 crystal faces, which corresponds to the lowest value that h, k, snd 0 can each represent. A regul~r tetrahexahedron hsving {310), {320}, {410~, {430}, {510}, {520}, {530}, or {540} crystal faces would appear similar to the tetrahexahedron 11, but the higher Miller indices would result ln changes in the ~ngles of intersection. Although there is no theoretical limit on the maximum values of the integers h and k, tetrshexahedral cryst~l faces hsving a value of h or k of 5 or less are more e~sily generated. For this reason, silver halide grains having tetrahex~hedrsl crystal faces of the exemplary Miller index values identified above are preferred. With practice one tetrshexahedral crystal face can often be distin-guished visually from another of a different Miller index value. Measurement of relative angles permits positive corroboration of the specific Miller index value tetr~hexahedr~l crystal faces present.
In one form the emulsions of this invention contain silver halide grains which are bounded entirely by tetrshexahedral crystal faces, thereby forming basically regular tetrahexahedra. In practice although some edge rounding of the grains is usually present, the unrounded residual flst tetrahexahedral fsces permit positive identification, since a sharp intersecting edge is unnecessary to establishing the relative angle of ad~acent tetra--hexahedral crystal faces. Sighting to orient the grsins is still possible employing the residual flat crystal face portions.
The radiation sensitive silver halide grains present in the emulsions of this invention are not confined tn those in which the tetrahexahedral crystal faces are the only flat crystal faces present. Just as cubo-octshedral silver halide grains, such as 9 and lO, exhibit both cubic and octehedral crystal faces and Berry, cited above, reports grain~ having cubic, octahedral, and rhombic dodecahedral crystal faces in a single grain, the radiation sensitive grains herein contemplated can be formed by tetrahexahedral crystal faces in combina-tion with any one or combination of the other types of crystsl faces possible with a silver halide cubic crystal lattice structure. For example, if conven-tional silver halide grains having cubic, octahedral,and/or rhombic dodecahedral crystsl faces are employed as host grains for the preparation of silver halide grains having tetrahexahedral crystal faces, stopping silver halide deposition onto the host grains before the original crystal faces have been entirely overgrown by silver hallde under conditions favoring tetrahexahedral crystal face formation results in both tetrahexahedral crystal faces and residual crystal faces corresponding to those of the original host grain being present.
In another variant form depositlon of silver halide onto host grains under conditions which favor tetrahexahedral 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 surface.
Protrusions in the form of ridges have been observed, ~'~ 8~X~ 6 but protrusions, when present, are more typically in the form of pyramids. Pyramids presenting tetrahexs-hedral crystal faces on host grains initially presenting {100} 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 cluster described above in connection with the tetrahexahe-dron 11. When the host grains initially present {111} crystal faces, pyramids bounded by 5iX
surface faces are formed. Turning to Figure 8, the apex of the pyramid corresponds to the coign formed faces 12a, 12b, 13a, 13b, 14a, and 14b. The protrusions~ whether in the form of ridges or pyramids, can within a short time of initiating precipitation onto the host 8rains substantially co~er the original host grain surface. If silver halide deposition is continued after the entire grain surface is bounded by tetrahexahedral crystal faces, the protrusions become progressively larger and eventually the grains lose their ruffled appearance as they present larger and larger tetrahexahedral crystal faces. It is possible to grow a regular tetrahexahedron from a ruffled grain by continuing silver halLde deposition.
Even when the grains are not ruffled and bounded entirely by tetrahexahedral crystal faces, the gralns can take overall shapes differing from regular tetrahexahedrons. Thls can result, for example, from irregularities, such as twin planes, present in the host grains prior to growth of the tetrahexahedral crystal faces or introduced during growth of the hexoctahedral crystal faces.
The important feature to note i5 that if any crystal face of a silver halide grain is a tetrahexa-hedral crystal face, the resulting grain presents aunique arrangement of surface silver and halide ions - that differs from that presented by all other ~'~8~,'Z,'f~6 possible crystal faces for cubic crystal lattice structure silver halides. This unique ~urface arrangement of ions as theoretically hypothesi~ed is schematicslly illustrated by Figure 10, wherein A
{210} tetrahexahedral crystsl 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 {210~ tetrahexahedral crystal face presents an ordered, but more varied arrangement of surface silver and bromide ions than is presented at the cubic, octahedral, or rhombic dodecahedral ilver bromide crystal faces. This is the result of the tiering that occurs at the 1210} tetrahexahedral crystal face. Tetrahexahedral crystal faces with differing Miller indices also exhibit tiering. The differing Miller indices result ln analogous, but nevertheless unique surface arrangements of silver and halide ions. The difference between tetrahexahe-dral crystal faces of differing Miller indices is illustrated by comparing Figure 10, which is a hypothetical schematic diagram of a {210~ crystal face, and Figure 11, which is a corresponding diagram of a ~410} crystal face.
While Flgures 2, 4, 6, 10, and 11 all contaln bromide ions as the sole hallde ion~, it is appreciated that the same observations as to differences in the crystal faces obtsin when each wholly or partially contains chloride ions instead.
Although chloride ions are substantially smaller in effectlve diameter than bromide ions, a tetrahexahe-dral crystal surface presented by silver chloride ions would be similar to the corresponding silver and bromide ion surfaces.
The cubic crystal lattice structure silver halide grains containing tetrahexahedral crystal faces can contain minor amounts of iodide ions, similarly as conventional silver halide grains.
Iodide ions have an effective diameter substantially larger than that of bromide ions. As is well known S in silver halide crystallogrsphy, this has a somewhat disruptive effect on the order of the crystal qtructure, which can be accommodated and actually employed photogr&phically to advantsge, provided the iodide ions are limited in concentration. Preferably iodide ion concentrations below 15 mole percent and optimally below 10 mole percent, based on silver, are employed in the practice of this invention. Iodide ion concentration~ of up to 40 mole percent, based on silver, can be present in silver bromide crystals.
Since iodide ions as the sole halide ions in silver halide do not form a cubic crystal lattice structure, their use alone has no applicability to this invention.
It is &ppreciated that the larger the proportion of the total silver halide grain surface area sccounted for by tetrahexahedral crystal faces the more distinctive the silver halide grains become. In most instances the tetrahexahedral crystal faces account for at least 50 percent of the total surface area of the silver halide grains.
Where the grains are regular, the tetrahexahedral 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, silver halide grains having tetrahexahedral crystal faces accounting for at least 90 percent of the total grain surface area are contemplated.
It is, however, sppreciated that distinctive photographic effects may be realized even when the tetrahexahedral crystal faces are limited in areal extent. For example, where in an emulsion containing the silver halide grains a photographic addendum is present that shows a marked adsorption preference for a tetrahexahedral crystal face, only a li~ited percentage of the totsl grain surf~ce m~y be required to produce a distinctive photographic eff~ct.
Generally, if ~ny tetrahexahedral crystdl face is observable on a silver halide grain, it sccounts 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 a tetrshexahedral crystal face becomes large enough to be identified by it~ relative angle to ad~scent crystal faces, it is already large enough to be capable of influencing photographic performance.
Thus, the minimum proportion of total grain surface area accounted for by tetrahexahedral crystal faces is limited only by the observer's ability to detect the presence of tetrahexahedral crystal faces.
The successful formation of tetrahexahedral crystal faces on silver halide grains of a cublc 2~ crystal lattice structure depends on identifying 3ilver halide grain growth conditions that retard the surface growth rate on tetrahexahedral crystal planes. It is generally recognized in silver halide crystellography thst the predominant crystal faces of a silver halide grain are determined by choosing grain growth conditions that are least favorable for the growth of that crystal face. For example, regular cubic silver hslide grains, such as grain 1, are produced under grain growth conditions that favor more rapid deposition of silver end halide ions on all other svailable crystal faces than on the cubic crystal faces. Referring to Figure 7, if an octahedral grain, such as regular octahedrfll graln 5 is sub~ected to growth under conditions that least favor deposition of silver and halide ions onto cubic crystal faces, grain 5 during continued silver halide precipitation will progress through the intermediate -~8-cubo-octahedral grain forms 9 ~nd 10 before reaching the final cubic grain configuration 1. Once only cubic crystal feces remain, then silver and halide ions deposit isotropicslly on these ~urfaces. In other words, the grain shape remains cubic, and the cubic grains merely grow larger A5 additional silver and halide ions are precipitated.
By analogy, grains having tetrahexahedral crystal faces have been prepared by introducing into a silver halide precipitation reaction vessel host grains of conventional crystal faces, such as cubic grains, while maintaining growth conditions to favor retardin8 silver halide deposition along tetrahexahe-dral crystal fsces. As silver halide precipitation continues tetrahexahedral crystal faces first become identifiable and then expand in area until eventual-ly, if precipitation is continued, they account for all of the crystal faces of the silver halide grains being grown. Since tetrahexahedral 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 generally known in the art to favor either continued grain growth or renucleation.
Failure of the art to observe tetrahexahe-dral crystal faces for sllver halide grains over decades of intense investigation as evidenced by published silver halide crystallographic studies suggests that there is not an extensive range of conditions that favor the selective retarding of silver halide deposition along tetrahexahedral crystal faces. It has been discovered that growth modifiers can be employed to retard silver halide deposition selectively at tetrahexahedral crystal faces, thereby producing these tetrahexahedral crystal faces as the external surfaces of the silver halide grains being formed. The growth modifiers ~.28~ 6 which hsve been identified are organic compounds.
They are believed to ~e effective by reason of showing an adsorption preference for a tetrahexahe-dral crystal face by reason of its unique arrangement S of silver snd halide ions. Growth modifiers that have been empirically proven to be effective in producing tetrshexshedrsl crystal faces are described in the examples, below.
These growth modifiers are effective under the conditions of their use in the examples. From empirical screening of a variety of cand~dste growth modifiers under differing conditions of silver halide precipitation it has been concluded that multiple parameters must be ~atisfied to schieve tetrahexehe-dral crystal faces, including not only the properchoice of a growth modifier, but also proper choice of other precipitation parameters identified in the examples. Failures to achieve tetrahexahedral crystal faceq with compounds shown to be effective as growth modifiers for producing tetrahexahedral crystal faces have been observed when accompanying conditions for silver halide precipitation hsve been varied. However, it ia appreciated that having demonstrated success in the preparations of silver halide emulsions containing grains with tetrahexahe-dral crystfll faces, roùtine empirical ~tudies systematically varying parameters are likely to lead to additional useful preparation techniques.
Once silver halide grain growth conditions are satisfied that selectively retard ~ilver halide deposition at tetrahexahedral crystal fsces, continued grain growth usually results in tetrahexa-hedral crystal faces ~ppearing on all the grains present 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 tetrshexahedral crystal faces. For example, silver halide grains having tetrahexahedral 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 tetrahexahedral crystal face grain surface are considered within the scope of this invention, in most applications the grains having at least one identifiable tetrahexahedral crystal face account for at lea~t 10 percent of the total grain population and usually these grains will account for 8reater than 50 percent of the total grain population.
The emulsions of this invention can be substituted for conventional emulsions to satisfy known photographic applications. In addition, the emulsions of this invention can lead to unexpected photographic advantages.
For example, when a growth modifier is present adsorbed to the tetrahexahedral crystal faces of the grains and has a known photographic utility that is enhanced by adsorption to a grain surface, either because of the more intimate association 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 tetrahexa-hedral crystal face it must exhibit an adsorption preference for the tetrahexahedral crystal face that is greater than that exhibited for any other possible crystal face. This can be appreciated by considering growth in the presence of an adsorbed growth modifier of a silver halide ~rain having both cubic and tetrahexahedral crystal face3. If the growth modifier shows an adsorption preference for the tetrahexahedral crystal faces over the cubic crystal face~, deposition of silver and halide ions onto the tetrahexahedral crystal faces is retarded to a 3L'~ 8~

greater extent than along the cubic crystfll faces, and gr~in growth results in the elimination of the cubic crystsl faces in favor of tetrahexahedral crystal faces. From the foregoing it i5 sppsrent S that growth modlfiers which produce tetrahexahedral cryst~l faces are more tightly sdqorbed to these gr~in surfaces than to other silver halide grain surfaces during grain growth, and this enhanced adsorption carries over to the completed emulsion.
To provide an exemplary photographic application, ~ocker U.S. Pstent 3,989,527 describes improving the speed of a photographic element by employing an emulsion containing radiation sensitive silver halide grsins having a pectral sensitizing dye adsorbed to the grain surfaces in combination with silver halide grains free of spectrsl sensitiz-ing dye having an average dlameter chosen to maximize light scattering, typic~lly in the 0.15 to 0.8 ~m range. Upon im~gewise exposure radiation striking the undyed grains is scattered rather th~n 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 disadvantsge encountered with this approach has been that spectral sen~itlzing dyes can migrate in the emulsion, so that to some extent the initially undyed grains sdsorb spectral sensitizing dye which has migrated from the initially spectrally sensitized grains. To the extent that the initially spectrally sensitized grains were optimally sensi-tized, dye migration away from their surfaces reduces 3ensitizstion. At the same time, adsorption of dye on the grains intended to sc~tter imaging radiation reduces their scattering efficiency.
In the examples below it is to be noted that specific spectral sensitizing dye hss been 3L'~ 8~ 6 -2~-identified as a growth modifier useful in forming silver h~lide grains having tetrahexahedral crystal faces. When radiation sensitive silver halide grains h~ving tetrahexahedr~l crystal faces and 8 growth modifier ~pectral sensitizing dye adsorbed to the tetrahexahedrsl crystal fsces are substituted for the spectrslly sensitized silver halide grains employed by Locker, the disedvant3geous migration of dye from the tetrahexahedral crystal faces to the silver halide grains intended to scatter light is reduced or eliminated. Thus, an improvement in photographic efficiency can be realized.
To illustrate another fldvantageous photo-graphic application, the layer structure of a multicolor photographic element which introduces dye lmage providing materials, such AS couplers, during processlng can be simpllfied. 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 i5 a red spectral sensitizing dye. Since the growth modifiers ~re tightly adsorbed to the grains and non-wandering, instead of coating the green and red emulsions in sepsrate color forming layer units, as is conventional practice, the two emulsions can be blended and coated as a single color forming lsyer 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 snd red recording emulsions in a single layer or group of layers differing 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 csn be extended to blending in a ~ingle color forming layer unit blue, green, and red recording emulcions~ and the yellow filter layer can be eliminated. The sdvantage ~n either case is a reduction in the number of emulsion layers required as compared to 8 corresponding conventional multi-color photographic element.
In more general spplications, the substitu-tion of an emulsion according to the invention containing a growth modifier spectral sensitizing dye should produce a more invariant emulsion in terms of spectral properties than a corresponding emulsion containing silver halide grains lacking tetrahexahe-dral crystal faces. Where the growth modlfier is capable of spectral sensitization, quch as the dyes shown to be effective growth modifiers in the examples, more effective spPctral sensitization at lower concentrations may be expected. It is recognized that a variety of photographic effects, such as photographic sensitivity, minimum background density levels, latent image stability, nucleation, developability, image tone, absorption, and reflec-tivity, are influenced by grain surface interactions with other components. By employing components, such as peptizers, silver halide solvents, sensitizers or desensitizers, aupersensitlzers, halogen acceptors, dyes, antifoggants, stabilizers, latent image keeping agents, nucleating agentc, tone modifiers, develop-ment acceleratorc or inhibitors, development restrainers, developing agents, and other addenda that are uniquely matched to the tetrahexahedral crystal surface, distinct advantages in photographic per~ormance over that which can be realized with silver halide grains of differing crystal faces are possible.
The silver halide grains having tetrahexahe-dral cry~tal faces can be varied in their properties ~L~ 8 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 Disclo ure, Vol. 176, December lg78, Item 17643, Section I, can be applied to the preparation of emulsions according to this invention.
Res_arch Disclosure is published by Kenneth Mason Publications, Ltd., Emsworth, Hampshire P010 7DD, England. The silver halide grains having tetrahexa-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 4,4~3,087 and 4,471,050.
The growth modifier used to form the tetrahexahedral crystal faces of the silver halide grains can be retained in the emulsion, adsorbed to the grain faces, displaced from the grain faces or destroyed entirely. For example, where, as noted above, the growth modifier is also capable of acting as a spectral sensitizing dye or performing some other usefu~ function, it i8 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, if 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.

A~1 ~8~

Apart from the novel grain structures identlfied above, the rsdistion sen~itive silver hsltde emulslons and the photographic element~ in which they sre incorporated of this invention can take any convenient conven~lonal form. The emulsion~
can be wsshed a5 described in Re3esrch Disclo~ure, Item 17643, cited above, Section II.
The radiation sensitive silver h~lide grains of the emul~Lons can be surfsce chemically ~ensi-tlzed. Noble metal (e.g., gold), middle chalcogen(e.e., sulfur, selenium, or t.ellurium), and reduction sensitizers, employed Individually or in combinstion are specifLcslly contemplated. Typical chemicsl en~Ltlzers sre listed in Resesrch Disclo~ure, Item t~643, clted Above, Section III. From comparisons of surface halide and silver ion arrangements in genersl the chemical sensltlzatlon re~ponse of silver halide grains hsvLng tetrahexahedral crystal faces should be analo~ous, but not ldentical, to that of cubic and octahedral silver halide grains. That ob~ervation can be extended to emulslon addenda generally which adsorb to 8rain surfaces.
The ~ilver hslide emulaionQ can be ~pectral-ly sensitized with dyes from a variety of clas~es, includin~ the polymethine dye class, which includes the cyanlnes, merocyanlnes, complex cyanines and merocyanines (l.e., trl-, tetra-, and polynuclesr cyQnines and merocyanines), oxonols, hemioxonols, styryl~, merostyryls, and streptocy~nine~. Illustra-tLve spectral sensitizinp, dyes are disclosed lnResearch Disclosure, Item 17643, cited above, Section IV.
The silver halIde emulsions a9 well as other layer~ o~` the photographic elements of this lnvention can contaLn as vehicles hydrophilic colloids, employed alone or in combination wLth other polymeric m~te~lal~ (e.p,., l~tices). Suitsble hydrophilic msterl~ nclude both naturslly occurring substances such ~s protelns, protein d2rlvetive~, cellulo~e der:lvst~ve~ -e.&., cel.lulose esters, gelatin -e.g., alkali tre~ted gel~tin ~cattle, bone, or hide gelatln) or acld treated gelatin (pig~kin gelstin), gelatLn deriv~tlves -e.g., ~cetylsted gelatin, phthslRted gelRtin, snd the like, polysaccharides such ~s dextr~n, gum arabic, zein, casein, pectin, collagen derivstives, collodion, agar-agsr, ~rrow-root, and albumin. It is specificRlly contemplRtedto employ hydrophi.llc colloid~ which contRin 8 low proportion div~lent sulfur atoms. The proportion of divslent sulfur atoms csn be reduced by treating the hydrophilic colloid with A strong oxidizing agent, such ss hydrogen peroxlde. Among p-referred hydroph:llic colloids for use 89 peptizers for the emulsions of this Lnvention are gelstino peptizers whlch contal.n less than 30 micromole~ of methionine per ~ram. The vehicles can be hardened by ~0 conventlonal procedures. Further detsils of the vehicles and hsrdeners Rre provided in Rese~rch Disc~osure, Item 17643, cited above, Sectlons IX and X.
The silver halide photogrsphic elements of this inventton csn contsln other sddends conventionsl ln the pht)togrsphic art. Useful addends are descrlbed, for example, in Research Disclosure, Item 17643, cil:ed above. Other conventionsl useful sddends lnclude sntlfoF,gsnt~ Rnd stsbilizers, couplers (such as dye forming couplers, masking couplers and DIR couplers) DIR compounds, anti-stain sgents, imagP. dye stabilizers, absorbing materials such 8S fi.lter dyes Rnd UV Qbsorbers, light scatter-in~ materlals, antistatic agents, coating sids, snd plssticizers and lubricant~.
The photogrRphLc element~ of the preqent .Inventlon cRn be ALmple blsck-and-whlte or monochrome ~,~8~6 elements compris~ng a ~upport bearing R layer of the silver hsllde emulslon, or they can be multilayer ~nd/or multicolor elements. The photogr&phic elements produce lma~es ranging from low contrast to very hlgh contrest, such as tho~e employed for producing hQIf tone im~ges in graphic arts. They can be designed for processing w~th ep~rate solutions or for ~n-camera processin~. In the latter instance the photogrAphic elements c~n include conventional im~ge transfer features, quch ss those illustrated by Research Disclosure, Item 17643, cited above, Section XXIII. Multicolor elements contain dye imsge forming unlts sensltlve to each of the three primsry regions of the spectrum. E~ch unit csn be comprised of a lS single emuls~on layer or of multiple emulsion lsyers sensltlve to a given reglon of the spectrum. The layers of the element, lncluding the layer3 of the lmsge formlng units, csn be ~rrsnged in various order~ as known in the srt. In sn alternQtive format, the emulsion or emulsions can be disposed ss one or more seemented lsyers, e.e., as by the use of microvessels or microcells, as described in Whitmore .S. Pstent 4,387,154.
A preferred multicolor photogrsphic element accordln~, to this Lnvention containing incorporated dye image providing materials compriseQ R support bearlnR at least one blue sen~itive ~ilver halide emul.slon layer hsving sssocisted therewith a yellow dye forming coupler, at lesst one green sensitive sl.lver halide emulsion layer hsving a~sociated therewith a mep,ents dye forming coupler, and st lesst one red sensi.tive sl.lver hAlide emulsion layer having assoclQted therewith a cyan dye forming coupler, at lesst one of the silver halide emulsion layers contsinLnR grains h~vLng tetrahexahedral crystal fsces a~ previously described.

~.~81'~ 6 The elements o~ the pre~ent invention can cont~ln ~ddltlonal layer~ conventional in photo-gr~phic elements, such ~s overcoat layer3, spacer layers, ftlter layer~, antihalation lsyer~, and sc~venger l~yers. The ~qupport csn be sny suit~ble support u~ed with photop,raphLc elements. Typicsl supports include polymer~c ~llms, paper (including polymer-coated paper), glass, snd metal supports.
Detail~ regarding supports and other layers of the photoKraphic elements of this invention are contsined in Research Disclosure, Item 17643, cited sbove, Section XVII.
The photogr~phic elements can be imagewise exposed with varlous forms o~ energy, which encompass the ultrsviolet, vlslble, and infrsred regions of the electroma~netlc spectrum ~5 well Q9 electron beam and bets radiation, gsmms ray, X rsy, slpha particle, neutron radi~tion, and other forms of corpuscular snd wave-llke rsdiant energy in either noncoherent (random pha~e) forms or coherent (io phase) form~, as produced by lsser~. When the photo~raphic elements sre intended to be expo~ed by X rays, they can include festures found ~n conventionsl rsdiographic element~, such ss those illustrated by Research Dlsclosure, Vol. 184, Aup,ust 1979, Item 18431.
Proce~slnp, of the im~gewise expo~ed photographic elements csn be accompllshed in any convenient conventional m~nner. Processing procedures, developing agents, snd development modlflers sre illustrated by Research Disclosure, Item 17643, ctted above, Sections XIX, XX, snd XXI, respectively.
Examples The invention can be better appreci~ted by reference to the following ~pecific examples. In each of the examples the term "percent" means percent by weight, unless otherwlse indicated, snd all ~olutLons, unless otherwi~e indicated, are a4ueous solutions. Dilute nitric acid or dilute Rodium hydroxide was employed for pH ad~ustment, ~s required.
Ex~mPle 1 Thls ex~mple illustrate,~ the prep~ration in the presence of ammoni~ of a tetrahexahedrsl ~ilver bromide emulslon having the Miller index 121Q}, beginnin~ wlth 8 cubic host emulsion.
To a re~ctlon vessel ~upplied with a stirrer was added 0.5 g. o deionized bone ~elatin dissolved in 28.5 ~. of water. To this was added 0.05 mole of a cubic sllver bromide emulsion of mesn grain ~ize 0.8~m containing ~bout lO g/Ag mole of gelatin snd havinF, a total wei~ht of 21.6 g. The emulsion was heated to 40C, and 3.0 mlllimoles~Ag mole of Dye I
dissolved in 2.5 mL. water was ~dded. The mixture WRS held at 40C for 15 min.
Dye ICIH3 / \ -N-cH-co2H
li =CH-~H=./ \ =S
\ / \S/
(C~l2)3sO3N~
.Just prior to beglnning the precipitation, 25 3.4 mlllimoles of an aqueous (NH4)2S04 solution (l.0 mL) W~9 added, followed by 25.9 millimoles of ammonium hydroxide (1.'75 mL) and 0.25 millimoles of KBr ~olution (0.5 m~). The pA~ was measured as 9.3 at 40C, and was maintained through the precipit~-30 tlon. At 40C Q 2.5M solution of AgNO3 was added at a constant flow rate along with a 2.5M solution of KBr, which W8S ~dded as necessary to maintain the pAp~. The preclpltation consumed 0.0175 mole Ag in 35 min. The pH was then slowly ad~usted to 5.5.
A carbon replica electron micrograph (Figure 12) shows Emulsion l to have tetrshexahedral faces.
The Mltler Index of the tetrahexahedral faces was ~8"1'~6 determined by measurement of the relative ~ngle between two ad~Rcent tetrahexahedral cryst~l faces.
From this an~le, the ~upplement of the rel~tive angle, which lg the angle between their respective crystsllographic vector~, ~, could be obtained, and the Miller index of the ad~acent tetrahexshedrsl crystal faces W9S ldentlfied by comparison of thi~
angle ~ wlth the theoretical Intersecting Angle e between ~hlk101] and [h2k202]
The sngle ~ waq calculated as described by Phlllips, cited sbove, ~t pages 218 and 219.
To obt~in the angle ~, a carbon replic~ of the crystal ssmple was rotated on the ~tage of sn electron microscope until, for a chosen crystal, the anele of observatlon was directly along the line of Intersectlon of the two sd~acent crystal faces of lnterert. An electron micrograph was then made, snd the relative angle wa~ measured on the micrograph with a protrsctor. The supplement of the meaqured relatlve angle was the an~le ~ between vectors.
Compsrison of ~ with ~ enabled the crystal faces to be s~signed. If the experimentslly determined anKle was nearly mid-way between two theoretic~l angles, the one associated wlth the lower Miller ~ndex was used for the sssip,nment. The re~ults for Emulslon l were ~9 follows. The number of measure--ments m~de ls p,lven ln parentheses. Theoretical values for vectors up to {5407 were considered.
Theoretical Anp~le Between Vectors {210) 35.9 ~3107 53.1 {3207 22.6 {410~ 61.9 {4307 16.3 Measured 39.3+1.3(11) Emulsion 1 is thus compo~ed of regular tetr~hex~hedra showing {210} faces.

8~ 6 Exs~ple 2 Thls example illustr~teq the prep~r~tion under non-ammoniacal condi~ions of a 4ilver bromide emulslon havlng ~raln~ with Miller index {410}
cryst&l faces be~inning with A cubic host emulsion.
To 8 resction veqsel 3upplied with a stirrer waq ad~ed 0.05 mole of the s~me host emul~ion as u~ed ln Ex~mple I (about 10 g/Ag mole ~el~tin) made up to S0 g. wlth w~ter. To thl~ was added 2 millimoles/Ag mole of Dye II dlssolved in 2 ml. of N,N-dimethyl-formamide.
Dye II ~ \ ~S

~ ~ \ ~ CH3C6H4S3-Et Et The mixture wa~ held at 40C for 15 min.
The pH was ad~usted to 6.0 at 40C, ~nd the emulsion W8~ heated ~o 60C. The pAg wa~ ad~usted to 8.5 at 60C with KBr and m~intained at that v~lue during the precipitation. A 2.0 M solution of AgNO3 ~nd ~ 2.0 M ~olutlon of KBr were then s~multsneou~ly added over a period of 50 mln. The A~NO3 solution wa~ ~dded at a conYtant r~te and 0.01 mole~ Ag were ~dded.
F1gure 13 is an electron micrograph of the re~ultlnp, emulslon, showin~ the crystals to have regular tetrahexA}ledral hab~t. The Miller index, dP,terml.ned ~9 descrLbed ~or Example 1, W~9 found to be {410}.
An~ Between Vectors Theoretical 1410} 28.1 Measured 29.4~1.3~5) Example 3 Thls example 111ustrates the preparation of snother tetrahex~hedral emulslon having a ~410}
Miller lndex, but usin~ a different growth modifier.
The emulsion was prepsred ~s described for Example 2, but for Dye II wes subs~ltuted Dye III, 4 milli-mole~/A~ mole, dissolved in 3 mL. wster. The preclpltstion W8S carried out for 50 min. ~t a rste consumlng 0.02 mole Ag.
Dye III 0 li ~ =C}~-CH=~ (CH2)3c2H

(CH2)3SO3 Na Fi~ure 14 ls sn electron mlcrogrsph of Emulsion 3 3howing the crystsls to hQve a regulsr tetrahexahe-drsl hablt. The Miller index wa~ determined ~Q
descrlbed in Example l and found to be ~410}.
An~le Between Vectors Theoretical {410} 28.1 61.~
Me~sured 25.5+0.5(2) 64.4il.4~(9) ExsmPle 4 Example 4 illustrates the preparation of a ~ilver bromLde tetrahexahedral emulsion having a ~4101 Miller index by the Ostwald ripening of a Lippm~nn emulslon onto a mixture of cubic ~nd octahedral host ~rslns ln the presence of a growth modifier.
To a reaction vessel wss ~dded 32.5 g. (7.5 milllmole) of a freqhly prepsred AgBr Llppmsnn emulslon of mean prain slze 0.02~1m snd containing 167 p,/Ap, mole o~ gelstin. At 35~C, 0.09 millimole of Dye IV ln 2 ml, of methsnol containing 2 drops of triethylamine was added.
Dye IV 0 Il ~ =C~-CH= \ ; ~-CH2cH2c2H

(CH2)3S03 N~+

~ ~ 8 Then 3.0 ml, 7.5 mill~moles of AgBr consisting of mixture of two emulsion~ containing &pproximately equal numbers of cubes (0.8~m mean size; 10 g/Ag mole gelatin) snd octahedra ~0.8~m mesn size; 10 S g/Ag mole ~elatln) W8S added. The pH wss ~djusted to 6.0 at 40C, and the pAg to 9.3 with KBr solution.
The mixture was then heated to 60C ~nd ~tirred st that temperature for 19 hrR.
Fieure 15 is ~n electron micro8raph of the resultin~ emulsion, ~howlng the crystals to have a regular tetrahexahedral habit. The Miller index was determined to be {410~.
Anp~le Between Vectors Measured 2~.0*l.4(5) 64.0il.0(3) Theoretical ~410} 28.1 61.9 Example 5 Example 5 illustrates the preparetion of a silver bromlde tetr~hexahedral emul~ion by Ostwald ripening, but u~ing Dye III instead of Dye IV 8 Browth modlfier.
The emulsion of Example 5 was prep~red as described for Example 4, but using as growth modifier 0.09 millimole of Dye III dlssolved in 3 mL of methanol, 1 mJJ of N,N-dimethylformamide, and 2 drops of tri.ethylamlne. An electron micrograph of the resultin~ emulsion ts shown in Figure 16. The hAbit ls ~ regular tetrahexahedron, with {410} faces.
ExamPle 6 Thi~ example illustrates the preparation of a tetrahexadral si.lver chloride emulsion having the Mi.ller index ~410}.
To a reaction vessel supplied with a stirrer was added 0.05 mole of 8 cubic silver chloride emulsion of mean ~,r~ln ~l~e 0.65 ~m and containing 40 g/Ag mole geletln. Water was added to mAke the total weight 48 p~. To the emulsion at 40C was added 2.0 mill~mole/Ag mole of Dye III dis~olved in 2 mL of w~ter. The emulsion W~5 then held for 15 min. at 40G. The temp~,rsture ws~ then r~i~ed to 50C. The pH ws~ ~dJu~ted to 5.9~ ~t 50C And maintained st this v~lue dur~ng the precipitstion by NsOH sddi-S tion, The pAg WS3 ~d~usted to 7,9 ~t 50C with NsCl~olution snd msintained during, the precipitatlon. A
1.5M solution of AP~NO3 w~s introduced at A con~tant r~te over s pertod of 500 min., while 8 2.7M solution of NsC] W8S sdded ss needed to hold the pAg constsnt. A totsl of 0.075 mole Ag wss added.
An electron micro~raph of the resulting tetrshex~hedral emulsion 8r~ins is shown in Figure 17. The h~blt W8S a regulsr tetr~hexahedron, snd the Miller index w~s determined to be {410).
An~.le Between Vectors Me~sured 25.9il.3(8) 64.0il.6(10) Theoreticsl {410~ 29.1 61.9 Exsmple 7 Thls exsmple illustrstes sdditional growth modl~iers cgp~ble of producing tetr~hex~hedr~l crystsl ~`aces and lists potenti~l growth modifiers inve~tig~ted, but not observed to produce tetrshex~-hedrsl cryst~l fsces.
The 8rsin growth procedures employed were of three different types:
A. The fir~t ersin growth procedure was BS
follows: To 8 resction vessel supplied with 8 stlrrer w~s 8dded 0.5 ~ of bone 8elstin dissolved ln 28.5 ~ of wste~. To thls w~s Qdded 0.05 mole of sllver bromide host 8rsin emulsion of mesn grsin size 0.8llm, contslninR ~bout IOg/A~ mole gelstin, snd having 8 totsl welght of 21.6 g. The emul~ion W89 hested to 40C, ~nd 6.0 millimoles/Ag mole of dissolved growth modlfie~ were ~dded. The mixture W8S held for 15 mln, ~t /tOC. The pH ws~ ~d~usted to 6.0 ~t 40C. The emulsion w~s then hested to 60C, snd the pAg wss sd~usted to 8,5 st 60C with ~ X ~6 KBr and ma1nts1ned at that value during the precipi-tat1On. The pH, which shifted to 5.92 ~t 60C, wa~
held at that value thereafter. A 2.5M solution of ARNO3 and a 2.5M ~olution of KBr were then introduced w~th A con~tRnt gilver addition rate over a perLod of 125 min., consuming 0.0625 mole Ag.
B~ The second p~rain growth procedure was a9 follow~: To a react1On vessel supplied with a ~tirrer was added 27.5 mL of water. To this W8 added 0.05 mole of 8 silver bromide host grain emulsLon of mean grain ~ize 0.8 ~m, conta~ning about lO g/Ag mole of p,elatin and havin~ a total weip,ht of 21.6 ~,. The emul~ion was heated to 40C, and 3.0 mLllimole/in1t1al A~ mole of dissolved growth modlfier waq added. The mlxture W~5 held at 40C for 15 mln. Just prior to beginning the precipitation .4 millLmoles of an aqueous (NH4)2S04 80lut~0n (l.0 mL), contaLnLng also 0.25 millimole of KBr, wa5 added, followed by 25.9 millimole~ of ammonium hydrox1de (2.0 mL). The pA~ wa~ meesured a~ 9.3 at 40~C and was maintained at that level throu8hout the preclpitation. At 40C a 2.5M solution of AgNO3 wa~ added at a constant flow rate along with a 2.5M
solutlon of KBr, the latter being added at the rate nece~sary to maintain the pAp~. The precipitatlon consumed 0.05 mole Ap, over a period of lO0 min. The pH was t}~en slowly ad~usted to 5.5.
In the fir~t and second procedure~ cubic or octalledraL hoAt gra1ns were employed as noted in Table I. Small ~smples of emulsion were withdrswn at intervals durln~ the precipitation for electron microscope examLnstLon, any tetrahexahedral crystal face~ revealed in such samples are reported in Table I.
C. The third grain growth procedure employed 7.5 millimoles of a fre~hly prepared very flne ~raln (approxlm~tely 0.02 ~m) AgBr emulsion to ~Z81 whlch W8S ~dded 0~09 millimole of growth modifier.
In thi~ proces~ these very fine AgBr grsins were dis~olved and reprecipitsted onto the ho~t gra~ns.
The ho9t gr~ln emulsion contaLned 0.8 ~m AgBr gr~lns. A 7.5 mlll~mole portion of the host gr~in emulsion w~s added to the very fine gr~in emulsion.
A pll of 6.0 snd pAg of 9.3 at 40 C was employed.
The mixture was stlrred at 60 C for about 19 hours.
The cry4tal fsces presented by the host grQlns are as noted in T~ble I. Where both octahe-drsl and cubic host gralns sre noted using the same growth modlfler, ~ mlxture of 5.0 millimoles cubic grslns of 0.8 l~ snd 2.5 millimoles of oct~hedr~l gralns of 0.8 ~m was employed giving approximately the same number of cubic and octshedral host grains.
In looklng at the grains produced by ripening, those produced by rlpenlng onto the cubic grains were resdily vLsu~lly distinguished, since they were larger. Thus, it WQS possible in one ripening process to determine the crystsl fsces produced using both cublc and octahedrsl host grains.
Dlfferences in individu~l procedures are indic~ted by footnote. The {hkO~ surface column of Table I refers to those surfaces which satisfy the definitlon ~bove for tetrahexahedr~l cryst~l faces.

~ 6 T A B_L E
{hkO) Host Growth Modifier Surfaces Grains Method 1 5-Nitro-o-phenyl-eneguanidine nitrate None cubic C
2 Citric acid, tri-.~odium salt None cubic C
3 5-Nitroindazole None cubic C
None octahedral C

4 1-Phenyl-5-mercap-totetr~zole None octahedral (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-1,2,3-benzo-triazole None cubic C

9 3-Methyl-1,3-benzo-thiazolium ~-toluenesul- None cubic C
fonate None octahedral C

10 4-Hydroxy-6-methyl-1,3,3a,7-tetra-azaindene~
sodium salt None octshedral C

11 4-Hydroxy-6-methyl-2-methylmercapto-1,3~3a,7-tetrfl-azaindene None cubic A

12 2,6,8-Trichloro- None cubic C
purine None octahedral C

T A B L E I (Cont'd) {hkO} Host Growth Modifier Surfaces Grains Method

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

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

15 5-Carboxy-4-hydroxy-1,3,3a,7-tetra- None cubic C
azaindene None octahedral C

16 5-Carbethoxy-4-hy-droxy-1,3,3a,7-tetraazaindene None cubic A
15 17 5-Imino-3-thiour- None cubic C
azole None octahedral C
18 2-~ormamidinothio-methyl-4-hydroxy-6-methyl-1,3,3a,7- None cubic C
20tetraazaindene None octahedral C
19 4-Hydroxy-2-~-hy-droxyethyl-6-methyl-1,3,3a,7- None cubic C
tetraazaindene None octahedral C
6-Methyl-4-phenyl-mercapto-1,3,3a,7- None cubic C
tetraazaindene None octahedral C
21 2-Mercaptc-5-phenyl- None cubic C
1,3,4-oxadiazole None octahedral C
3~ 22 l,10-Dithia-4,7,13,16-tetra- None cubic C
oxacyclooctadecane None octahedral C
23 2-Mercapto-1,3- None cubic C
benzothiazole None octahedral C
35 24 6-Nitrobenzim~dazole None cubic (3) A
25 5-Methyl-1,2,3- None cubic C
benzotriazole None octahedral C

~xal-~z~
-3~-T A B L E I (Cont'd) {hkO} Host Growth Modifier Surface~ Grsins Method 26 Urazole None cubic C
None octahedral C
27 4,5-Dicarboxy-1,2,3-triazole, None cubic C
monopota~sium 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
30 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-thiohydantoin None cubic A
33 Ethylenethiourea None cubic A
None octahedral A
34 2-Carboxy-4-hydroxy-6-methyl-1,3,3a,7- None cubic C
tetraazaindene None octahedral C
35 ~ithiourszole None cubic C
None octahedral C
36 2-Mercaptoimidazole None cubic A
37 5-Carblethoxy-3-(3-carboxypropyl)-4-methyl-4-thia- None cubic C
zoline-2~thione None octahedral C
38 Dithiourazole-methyl vinyl None cubic C
ketone monoadduct None octahedral C
39 1,3,4-Thiadiazoli- None cubic C
dine-2,5-dithione None octahedral C

~ X 8 T A B L E I (Cont'd) , {hkO} Host Growth Modifier Surfaces Grains Method 40 4-Carboxymethyl-4-thiazoline- None cubic C
2-thione None octahedral C
41 1-Phenyl-5-selenol-tetrazole, octahedral potassium salt None (1)(2) A
10 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
1-(3-Acetamido-phenyl)-5-mercap-totetrazole, sodium 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
48 ~-ThiocsprolactAm None cubic (1) A
49 4-Hydroxy-2-methyl-thiO-l~3~3a~7-tetraazaindene None cubic A

l.X81 T A B L E I (Cont'd) {hkO} Ho~t ~rowth Modifier Surfaces Gr~in-~ Method 50 4-Hydroxy-2,6-di~
methyl-1,3,3a,7- octahedral tetraazaindene None (4) A
51 Pyridine-2-thiol None octahedral (8) A
52 4-Hydroxy-6-methyl-1~ 1,2,3a,7-tetra- octahedral azaindene None (4) A
53 7-Ethoxycarbonyl-6-methyl-2-meth-ylthio-4-oxo-1,3,3a,7-tetra-azaindene None 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-benzimidazole None octahedral A
57 Benzenethiol None octahedral (1)(8) A
25 58 Melamine None cubic C
None octahedral C
59 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
62 4-Methoxy-6-methyl-1,3,3a,7-tetra-azaindene None octahedral A

~ 2 6 T A B L E I (Cont'd) {hkO} Host Growth Modifier Surfaces Gr~ins Method 63 4-Amino-6-methyl-1,3,3a,7-tetra 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-imida7.01e None octahedral A
69 3-Ethyl-5-~(3-ethyl-2-benzoxazolinyli-dene)ethylidene]-4-phenyl-2-thioxo-3-thiazolinium None cubic C
iodide None octAhedral C

Tf \-' \ CH / ~ I~
~ / \N/ \S/ ~S

Et 70 3-Ethyl-5-(4-methyl-2-thioxo-3-thia-zolin-5-ylidene- None cubic C
methyl)rhodanine None octahedral C
o Me 1!
Et- ~ \--C=- / ~

T A B L E I (Cont'd) ~hkO} Host Growth ModifierSurfaces Grains Method 71 3-Isopropyl-[(3-ethyl-2-benzothis-zolidinylidene)-ethylidene]rho-danine None cubic B

~ / \ ~ \ / ~ ~ e 72 3,3'-Diethylthia-cyanine ~-toluene ~ulfonate {410} cubic (5) A

~ ~ -CH=~
I
Et Et pt~
73 3-Ethyl-5-(3-ethyl-2-benzothiAzolin-ylidene)rhod~nine None cubic (5) A
~S
~I \.=./ ~ -Et ~/ \N/ \ S/ ~S
Et T A B L E I (Cont'd) ~hX0} Host Growth Modifier Surfaces Grflins Method 74 3-Ethyl-5-(3-ethyl-2--benzothiRzo--linylidene)-2-thio-2,4-oxazoli-dinedione None cubic (5) A

li \ =. / ~ -Et Et 15 75 5-(3-Ethyl-2-benzo-thiazolinylidene)-1,3-diphenyl-2- None cubic C
thiohydantoin None octahedral C

Et 25 76 3-Ethyl-5-(3-ethyl~
2-benzoxazolinyl-idene)rhodanine None cubic (5) A
o 30 i~-\-/o\ /!\y_ Et ~-/ \N/ ~S/ ~S

Et T A B L E I (Cont'd) {hkO} Host Growth ModifierSurfaces 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 oct~hedral C
~ ~ e O

i~ /i\ ? =CH CH \ ;~

Me Me 78 5-(1,3-Dithiolan-2-ylidene)-3-ethyl--rhodanine None cubic (5) A
o H2~ Et 79 5-(5-Methyl-3-pro--pyl-2-thiazolinyl-idene)-3-propyl-rhodanine None cubic (5) A
o 30 i1 ~- - \ ~i -CH2-cH2-Me C~H2 Me ~ 8~ 6 T A B L E I (Cont'd) {hkO} Host Growth Modifier Sur~aces_ Grains Method 80 3~Carboxymethyl-5-[(3-ethyl-2-benz-oxazolinylidene)-ethylidene]rho- None cubic C
d~nine None octahedral C

l~ /li ~ =CH-CH=~ CH2-C02H

Et 15 81 5-(3-Ethyl-2-benzo-thiazolinylidene)-3-~-sulfoethyl-rhodanine None cubic (5) A

T~ ' ,' \ = ./ ~--CH2 CH2 s 3 Et 82 5-Anilinomethylene-3-(2-sulfoethyl)-rhodanine None cubic (6) A
o l!
HSO3-CH2-CH2- ~ \-=CH-S~ \S

T A B L E ~I (Cont'd) ~hkO} Ho~t Growth Modifier Surface~_ Grains Method 83 3-(l-Carboxyethyl)-5-[(3-ethyl-2-benzoxazolinyli dene)ethylidene]-rhodanine None cubic B
Il CH-Me I li ~ =CH-CH=-\ ~ C02H

Et 5 84 3-~1-C~rboxyethyl)-5-[(3-ethyl-2-benzothiszo-linylidene)ethyl-idene3rhodanine None cubic B

i~ /li ~ =CH-CH=- / ~ lO H

Et B5 3-(3-Csrboxypropyl)-5-[(3-ethyl-2-benzoxazolinyli-dene)ethylidene]-rhodanine None cubic B

ll ~ =CH-CH=~ CH2-cH2-cH2-co2H

Et ~8~

T A B L E I (Co~t'd) {hkO} Host Growth Modifier Surfaces_ Grflin~ Method 86 3-(2-Carboxyethyl)-5-[(3-ethyl-2-benzothiazolinyli-dene)ethylidene]- None cubic C
rhodanine None octahedral C

=CH--CH= / ~--C H2--C H2C02H

87 3-C~rboxymethyl-5-[(3-methyl-2-thia-~olidinylidene)-isopropylidene]-rhodanine None cubic B

o ~ Me S S
Ms 88 3-Carboxymethyl-5-[(3--methyl-2-thia-zolidinylidene)-ethylidene]rhoda-nlne None cubic B
o H22-l\ ~ =cH-CH=.\ ~- CH2C2H

Me 1~ 81~2 T A B L E I (Cont'd) {hkO} Host Growth Modi~ier Surfaces_ Grains Method 89 3-Carboxymethyl-5-f[3-(2-carboxy-ethyl)-2-~hiazoli-dinylidene]ethyl-idene}rhodanine None cubic B
o ~S li H2_l\ ~ =CH-CH=-~ ~-CH2c2H

( Z)2C02H
5 go 3-(a-Carboxy-benzyl)-5-[(3-ethyl-2-benzoxazo-linylidene)ethyl-idene]rhodanine None cubic B

I~ Ij ~ =CH-CH=./ ~ -CHC02H

Et 91 3-(a-Carboxyben-zyl)-5-[(3-methyl-2-thiazolidlnyli-dene)ethylidene]-rhodanine None cubic B
O ,,~, ~s l!
HZ_I ~ =CH-C=.\ ~i CHCOzH

Me ~ X 6 T A B L E I (Cont'd) .
{hkO~ Host Gro~th ModifierSurfaces Grains Method . _ _ 92 1-Ethyl-4-(1-ethyl-4-pyridinylidene)-3-phenyl-2-thio- None cubic C
hydsntoin None octahedral C
o Et-N/ \.-. / \~- Et 93 Anhydro-3-ethyl-9-methyl-3'-(3-sul-fobutyl)-thia-carbocyanine None cubic C
hydroxide None octahedral C
S Me S
.~ \./ \ I / \ / ~
-CH=C-CH=-\ /11 ~I

Et CH2 Me 94 3-Ethyl-5-[1-(4-sul-fobutyl)-4-pyri-dlnylidene]rhoda-nine, piperidine None cubic C
~lt None octahedral C
o 3 2 4 \ _ / ~ /-~

~ H

T A B L E I ~Con~'d) lhkO} Host Growth Modifier Surfaces Gr~ins Method 95 5-(3-Ethyl-2-benzo-5thiazolinylidene)-l-methoxycarbonyl-methyl-3-phenyl- None cubic C
2-thiohydantoin None octahedral C
o S
Et ICH2 CaO

96 1,1',3,3'-Tetraeth-ylimidazot4,5-b)-quinoxalinocar-bocyanine P-tolu-enesulfonate None cubic B
Et Et 25 ~ =CH- CHaCH - ~i li i 1~ 1 Et pts Et 97 3-(2-Carboxyethyl)-5-(1-ethyl-4-pyridinylidene)- cubic rhodanine None (1)(2) A
o Et-N\ / = \ ~ CH2 CH2C02H

T A_B L E I (Cont'd) {hkO} Host Grow~th ModifierSurfaces Gr~in_ Method 9B 3-Carboxymethyl-5-{~3-(3-~ulfopro-pyl)-2-thiazoll-dinylidene]ethyl-idene}rhoda-nine, sodium salt None cubic (1) A
o Il H2-l ~ =CH-cH=. /; ~ -cH2-co2H

(CH2)3SO~ Na 99 3-(1-Carboxyethyl)-5-{[3-(3-sulfo-propyl)-2-thiazol-idinylidene]ethyl-2Q idene}rhoda-nine, sodium salt {210} cubic B

H2 T \ =CH-CH= / ~ -CH-C02H
H2-- N/ \s/ ~s (CH2)3S03 Na ~X81~26 T A B L E I (Cont'd~
lhkO~ Host Growth ModifierSurfaces Grains Method lO0 3-(3-C~rboxypropyl)-5-l[3-(3-~ulfo-propyl)-2-th~azol-idinylidene~ethyl-idene}rhoda-nine, sodium salt {410} cubic (7) A
o H2 I,~ CH CH=-\ ~-~CH2)3CO2H

(CH2)3S0~ Na lOl 3-(2-Carboxyethyl)-5-{[3-(3-sulfo-propyl)-2-thiazol-idinylidene~ethyl-idene}rhoda- {410} cubic C
nine, sodium ~alt {410} octahedral C
o H22_i ~ =CH-CH=- ~ ~- CH2-CH2C02H

(CH2)3S03 Na+

lX~12~6 T A B L E I (Cont'd) {hkO} Host Growth ModifierSurfaces Grains Method 102 3~Carboxymethyl-5-(2-pyrrolino-1-cyclopenten-l-yl-methylene)rhoda-nine, sodium salt None octahedral A
.~ ~.

~ \ =CH--~ \

103 3-Ethyl-5-(3-methyl-2-thiazolidinyli-dene)rhodanineNone cubic (5) A
o 20 H2-¦' \.=./ \y---Et Me 104 5-(4-Sulfophenyl-azo)-2-thiobarbi-turic acid, None cublc C
sodium ~lt None octahedral C
o 30 03S--~ N=N- I~ \yH
Na H

~ X~6 T A B L E I (Cont'd) lhkO} Host Growth Modifier Surfaces Grains Method 105 3-Carboxyme thy 1 - 5 -(2,6-dimethyl-4(H)-pyran-4-yli-dene)rhodanine None cubic (5) A
o M~ 11 M~ -- \5/ ~S
106 Anhydro-1,3'-bis(3-~ulfopropyl)naph-tho[l,2-d]-thia-zolothiacyanine hydroxide, tri-ethylamine salt None cubic (5) A

(CH2)3 (CH2)3~-/

S030 so3~ HNEt3 107 3-Ethyl-5-[3-(3~sul-fopropyl)-2-benzo-thiazolinylidene~-rhodanine, trieth-ylamine salt None cubic (5) A
o i~ li ~ =-\ ~- Et (CH2)3 SO~ HNEt3+

~X81XXf~

T A B_L E I (Cont'd) {hkO~ Host Growth ModlfierSurfaces Grsins Method 108 3-Ethyl-5-~3-~3-~ul-S fopropyl)-2-benz-oxRzolinylidene~-rhodQnine, potas- None cubic C
sium salt None oct~hedr~l C
o \l~/ \.=, / \~ - Et ~-/ \N/ \S/ ~S
(CH2)3S03 Kf (l) 3 mmoles of growth modifier/Ag mole of host p,rRln emul~ion was employed (2) a pBr of 1.6 w~s employed (3) 9 mmole~ of growth modifier/Ag mole of ho~t grQin emul~ion was employed, ~dded in two portions ~4~ 50C was employed instead of 60~C
(5) 2. mmoles of growth modifier/Ag mole of host grAin emulsion wa~ employed ~6) 1.5 mmoles of growth modifier/Ag mole of host gr~ln emulsion was employed 7) 4 mmoles of growth modifler/Ag mole of host grain emulsion W~9 employed (~) a pRr o~ 2.3 wss employed Exsmple 8 Thls example l.llustrates the modification of 8 p,rowth modifier used to prepare sn emulsion sccord$np~ to the invention contsining grQins with tetrshex~hedrs1. cryst~l fsces.
Two emuls~ons according to the invention cont~inlng gralns wLth tetr~hexahedr~l cryst~l f~ces were prepared uq:Lng prepar~tion procedures similsr to thQt descrl.bed in Ex~mple 1. Emulsion A consi~ted of ~ X8~ 26 -~7-pur~ sllver bromlde tetrahex~hedr~l grains while Emulslon B conslsted of silver bromoiodide (2.5 mole percent lodlde) tetrahexahedral grain~.
~oth Emul~lons A and B were pink in color, S the co]or being attributRble to Dye I (see Example 1) employed 8. a 8rowth modifier during their prepara-tlon. To each emulsion bromine wster was added with stirring. With ~he sddltion of the bromine w~ter the pink color completely disappeared, le~ving only a yellow color expected for the emulsions ahsent the presence of a spectral sensitizing dye.
Beyond illustrstlng how a growth modif$er CQn be effectlvely destroyed within an emulsion according to the ~nvention after its preparQtion, the example more 3pecificfllly illustr~tes that spectrsl sensltizlnÆ dye employed 8S a growth modifier can be de~troyed after emulsion preparation, if decired~ By destuction of the spectral sensitizer, the emulsion Ls placed in Q form in whlch it retains only it~
natlve spectral sensitivity, ~s ls desirflble for many known photographic applications. Alternstively, once the spectral senslti7.ing dye employed as a growth modifler has been effectively destroyed, ~nother spectral sensitizing dye can be adsorbed to the 8rain surfaces.
The invention has been described in det~il with pflrticutQr reference to preferred embodlments thereo~, but lt will be understood that vsriations snd modificfltions can be effected within the spirit and scope of the invention.

Claims (11)

WHAT IS CLAIMED IS:

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

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

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

4. A silver halide photographic emulsion according, to claim 1 wherein said silver halide grains comprised of tetrahexahedral crystal faces contain at least one of bromide and chloride ions and optionally contsin 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 octahedral crystal faces.

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

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

8. A silver halide photographic emulsion according to claim 1 wherein said tetrahexahedral crystal faces satisfy the Miller index assignment {hk?}, wherein 0 is zero, h and k are integers greater than 0, no greater than 5, and different from each other.

9. A silver halide photographic emulsion according to claim 8 wherein said tetrshexahedral crystal faces exhibit a {210} or {410} Miller index.

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 3,3'-diethylthiacyanine, 3-carboxy-ethyl-5-{[3-(3-sulfopropyl)-2-thiazolidinylidene]ethy lidene}rhodanine, and 3-carboxypropyl-5-{[3-(3-sulfopropyl)-2-thiazolidinylidene]ethylidene}-rhodanine dyes.

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