US3148066A - Nitramino and nitrosamino compounds as antifoggants for photographic emulsions - Google Patents

Description

United States Patent Office 3,148,655 Patented Sept. 8, 1964 3,14%,tl66 NITRAMTNQ AND NTTRAMKNO QOMPQUNDS AS ANTIFGGGANTS FQR PHGTOGRAPHKC EMULSEONS Colin Holstead, Harrow, Engiand, assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Brewing. Fiied June 29, 11961, Ser. No. 129,489 17 Claims. (U. 96-10% This invention relates to stabilized photographic compositions, and more particularly, to photographic silver halide emulsions containing novel fog-inhibiting agents.

It is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation; in this invention, we are not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is of course, desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

It is an object of this invention to provide a new method for stabilizing photographic emulsions.

It is another object of this invention to inhibit fog formation in photographic silver halide emulsions with novel addenda.

It is also an object of this invention to maintain with novel photographic addenda the sensitivity and fog of photographic silver halide gelatin emulsions at or close to initial optimum values under hi h temperature and high humidity keeping conditions.

These and other objects of the invention are accomplished by incorporating into photographic silver halide emulsions nitramino compounds containing the group NHNO or nitrosamino compounds containing the group NHNO. The emulsion addenda of the invention can be represented by the formulas XNHNO and XNHNO wherein X is an organic radical and typically can be such groups as p-toluenesulfonyl, imidazolyl, thiadiazolyl, tetrazaindenyl, triazolyl, thiazolyl, pyrimidinyl, thiazolsulfonyl, guanidino and the like groups, and including substituted derivatives thereof, as well as such hydrocarbon groups as alkyl groups of 1 to 20 carbon atoms including methyl, n-propyl, Z-ethylhexyl, n-decyl, stearyl, n-eicosyl and the like groups.

The addenda of the invention described above can be added to photographic silver halide emulsions for purposes of increasing the stability thereof. More specifically the subject addenda serve as emulsion antifoggants. Many antifoggant addenda cause substantial desensitization or loss in speed of the emulsion when employed therein in antifoggant amounts. However, with the subject addenda there is no substantial loss of speed imparted to emulsions. In many instances with the subject addenda there is actually imparted to emulsions an increase in sensitivity or speed, this being illustrated by the data set out in the detailed examples and tables hereinafter. It is known in the art that the addition of compounds containing -NO moieties to photographic silver halide emulsions is generally to be avoided as such compounds usually have substantial desensitizing effects. Hence, it is the exception when a compound or class of compounds is found that contain NO moieties and do not substantially desensitize photographic silver halide emulsions. The compounds of the invention contain not only a NO or -NO moiety but also a -NH moiety to form the active nitramino (NHNO and nitrosamino groups, these two groups containing amino and nitro or nitroso moieties which cooperate to lend to compounds containing such the improved properties described herein.

The preparation of photographic silver halide emulsions such as are suitably stabilized with the addenda of the invention typically involves three separate operations: (1) emulsification and digestion of silver halide, (2) the freeing of the emulsion of excess water-soluble salts, suitably by washing with water, and (3) the second digestion or after-ripening to obtain increased emulsion speed or sensitivity. (Mees, The Theory of the Photographic Process, 1954.) The stabilizers of our invention can be added to the emulsion before the final digestion or afterripening, or they can be added immediately prior to the coating.

The particular quantity of the present stabilizers used in a given emulsion can vary, depending upon the effects desired, degree of ripening, silver content of the emulsion, etc. We have found that generally from about .001 to 10 grams per mole of silver halide are quite adequate to accomplish the desired stabilization. Exposure of the treated emulsion in conventional photographic testing apparatus, such as an intensity scale sensitometer, will reveal the most advantageous concentrations for the present stabilizers in that particular emulsion. Such techniques are well understood by those skilled in the art.

The addenda of the invention can be added to photographic emulsions using any of the well-known techniques in emulsion making. For example, they can be dissolved in a suitable solvent and added to the silver halide emulsion, or they can be added to the emulsion in the form of a dispersion similar to the technique used to incorporate certain types of color-forming compounds (couplers) in a photographic emulsion. Techniques of this type are described in Jelley et al. US. Patent 2,322,027, issued June 15, 1943, and Fierke et al. US. Patent 2,801,171, issued July 30, 1957. The solvent should be selected so that it has no harmful effect upon the emulsion in accordance with usual practice, and generally solvents or diluents which are miscible with water are to be preferred. Water alone is a dispersing medium for some of the stabilizers of the invention. In other cases, the subject stabilizers can be dissolved in solvents, such as ethanol, acetone, pyridine, N,N-dimethylformamide, etc., and added to the emulsion in this form.

The emulsions of the invention can be chemically sensitized by any of the other well-known procedures. The

emulsions can be digested with naturally active gelatin, or sulfur compounds can he added, such as those described in Sheppard US. Patent 1,574,944, issued March 2, 1926, and Sheppard et al. 1,623,499, issued April 5, 1927, and Sheppard and Brigham US Patent 2,410,689, issued November 5, 1946. The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum. Representative compound are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli US' Patent 2,448,060, issued August 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith US. Patents 2,566,245, issued August 28, 1951 and 2,566,263, issued August 28, 1951. The emulsions can also contain sensitizing amounts of gold salts as described in Waller et al. US. Patent 2,399,083, issued April 23, 1946, or stabilizing amounts of gold salts as described in Damschroder US. Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers US. Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and Z-aurosulfobenzothiazole methochloride. The emulsions can also contain sensitizing amounts of reducing agents such as stannous salts (Carroll US. Patent 2,487,850, issued November 15, 1949), polyamines, such as diethylene triamine (Lowe and Jones US. Patent 2,518,698, issued August 15, 1950), polyamines, such as spermine (Lowe and Allen US. Patent 2,521,295, issued September 12, 1950), or bis(,8-aminoethyl)sulfide and its watersoluble salts (Lowe and Jones US. Patent 2,521,926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker US. Patents 1,846,301, issued February 23, 1932; 1,846,302, issued February 23, 1932; and 1,942,854, issued January 9, 1934; White US. Patent 1,990,507, issued February 12, 1935; Brooker and White US. Patents 2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950; and 2,739,964, issued March 27, 1956; Brooker and Keyes US. Patent 2,493,748, issued January 10, 1950; Sprague US. Patents 2,503,776, issued April 11, 1950 and 2,519,001, issued August 15, 1950; Heseltine and Brooker US. Patent 2,666,761, issued January 19, 1954;

Heseltine US. Patent 2,734,900, issued February 14,

1956; Van Lare US. Patent 2,739,149, issued March 20, 1956; and Kodak Limited British Patent 450,958, accepted July 15, 1939.

The emulsions can also contain speed-increasing compounds of the quaternary ammonium type of Carroll US. Patent 2,271,623, issued February 3, 1942; Carroll and Allen US. Patent 2,288,226, issued June 30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued November 23, 1943; and the polyethylene glycol type of Carroll and Beach US. Patent 2,708,162, issued May 10, 1955.

The emulsions can contain a suitable gelatin plasticizer such as glycerin; a dihydroxy alkane such as 1,5- pentane diol as described in Milton and Murray US. Patent 2, 960,404, issued November 15, 1960; an ester of an ethylene bis-glycolic acid such as ethylene bis- (methyl glycolate) as described in Milton US. Patent 2,904,434, issued September 15, 1959; his (ethoxy diethylene glycol) succinate as described in Gray US. Patent 2,940,854, issued June 14, 1960, or a polymeric hydrosol as results from the emulsion polymerization of a mixture of an amide of an acid of the acrylic acid series, an acrylic acid ester and a styrene-type compound as described in Tong US. Patent 2,852,386, issued September 16, 1958. The plasticizer may be added to the emulsion before or after the addition of a sensitizing dye, if used.

The emulsion can be hardened with any suitable hardener for gelatin such as formaldehyde; a halogen-substituted aliphatic acid such as mucobromic acid as described in White U. S. Patent 2,080,019, issued May 11, 1937; a compound having a plurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,2)-7-octene-2,3,- 5,6-tetracarboxylic dianhydride, or a dicarboxylic or a disulfonic acid chloride such as terephthaloyl chloride or naphthalene-1,5-disulfonyl chloride as described in Allen and Carroll US. Patents 2,725,294 and 2,725,295, both issued November 29, 1955; a cyclic 1,2-diketone such as cyclopentane-1,2-dione as described in Allen and Byers US. Patent 2,725,305, issued November 29, 1955; a hisester of methane-sulfonic acid such as 1,2-di-(rnethanesulfonoxy)ethane as described in Allen and Laakso US. Patent 2,726,162, issued December 6, 1955; 1,3-dihyr0xymethylbenzimidazol-2-one as described in July, Knott and Pollak US. Patent 2,732,316, issued January 24, 1956; a dialdehyde or a sodium bisulfite derivative thereof, the aldehyde groups of which are separated by 2-3 carbon atoms, such as fl-methylglutaraldehyde bissodium bisulfite; a bisaziridine carboxamide such as trimethylene bis(l-aziridine carboxamide) as described in Allen and Webster US. Patent 2,950,197, issued August 23, 1960; or 2,3-dihydroxy dioxane as described in Jeilreys US. Patent 2,807,013, issued January 20, 1959.

The emulsion can contain a coating aid such as saponin; a lauryl or oleoyl monoether of polyethylene glycol as described in Knox and Davis U.S. Patent 2,831,766, issued April 22, 1958; a salt of a sulfated and alkylated polyethylene glycol ether as described in Knox and Davis US. Patent 2,719,087, issued September 27, 1955; an acylated alkyl taurine such as the sodium salt of N-oleoyl- N-methyl taurine as described in Knox, Twardokus and Davis US. Patent 2,739,891, issued March 27, 1956; the

H reaction product of a dianhydride of tetracarboxybutane with an alcohol or an aliphatic amine containing from S to 18 carbon atoms which is treated with a base, for example, the sodium salt of the monoester of tetracarboxybutane as described in Knox, Stenberg and Wilson US. Patent 2,843,487, issued July 15, 1958; a watersoluble maleopimarate or a mixture of a watersoluble maleopimarate and a substituted glutamate salt as described in Knox and Fowler US. Patent 2,823,123, issued February 11, 1958; an alkali metal salt of a substituted amino acid such as disodium N-(carbo-p-tert. octylphenoxypentaethoxy) glutamate, or a sulfosuccinamate such as tetrasodium N-(1,2-dicarboxyethyl)-N-octadecyl sulfosuccinamate, or N-lauryl disodium sulfosuccinamate.

The stabilizer addenda of the invention can be used in various kinds of photographic emulsions. In addition to being useful in orthochromatic, panchromatic, and infrared sensitive emulsions, they are also useful in X-ray and other non-optically sensitized emulsions. They can be added to the emulsion before or after any optical sensitizing dyes which may be used. Various silver salts can be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide, or silver bromoiodide. The subject addenda can be used in emulsions intended for color photography, for example, emulsions containing colorforming couplers or emulsions to be developed by solutions containing couplers or other color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky US. Patent 2,698,794, issued J anuary 4, 1955, or emulsions of the mixed-grain type, such as described in Carroll and Hanson US. Patent 2,592,243, issued April 8, 1952. The subject stabilizers can also be used in emulsions which form latent images predominantly on the surface of the silver halide crystal or in emulsions which form latent images predominantly inside the silver halide crystal, such as those described in Davey and Knott US. Patent 2,592,250, issued April 8, 1952.

The subject addenda can also be used in emulsions intended for use in diffusion transfer processes which utilize the undeveloped silver halide in the non-image areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in Rott U.S. Patent 2,352,014, issued June 20, 1944, and Land U.S. Patents 2,584,029, issued January 29, 1952; 2,608,236, issued December 28, 1954, and 2,543,181, issued February 27, 1951. They can also be used in color transfer processes which utilize the diffusion transfer of an imagewise distribution of developer, coupler or dye, from a lightsensitive layer to a second layer, while the two layers are in close proximity to one another. Color processes of this type are described in Land U.S. Patents 2,559,643, issued July 10, 1951, and 2,698,798, issued January 4, 1955; Land and Rogers Belgian Patents 554,933 and 554,934, granted August 12, 1957; International Polaroid Belgian Patents 554,212, granted July 16, 1957, and 554,935, granted August 12, 1957; and Yutzy U.S. Patent 2,756,142, issued July 24, 1956.

In the preparation of the silver halide dispersions employed for preparing silver halide emulsions, there can be employed as the dispersing agent for the silver halide in its preparation, gelatin or some other colloidal material such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound, although gelatin is preferred. Some colloids which can be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe U.S. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 1926% as described in U.S. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; a Water-soluble ethanolamine cellulose acetate as described in Yutzy U.S. Patent 2,322,085, issued June 15, 1943; a polyacrylamide having a combined acrylamide content of 30-60% and a specific viscosity of 0.'251.5 on an imidized polyacrylamide of like acrylamide content and viscosity as described in Lowe, Minsk and Kenyon U.S. Patent 2,541,474, issued February 13, 1951; zein as described in Lowe U.S. Patent 2,563,791, issued August 7, 1951; a vinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith U.S. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest U.S. Patent 2,808,331, issued October 1, 1957; or a polymeric material which results from polymerizing a protein or a saturated acylated protein with a monomer having a vinyl group as described in Illingsworth, Dann and Gates U.S. Patent 2,852,382, issued September 19, 1958. If desired, compatible mixtures of two or more of these colloids can be employed for dispersing the silver halide in its preparation.

The above-described emulsions of the invention can be coated on a wide variety of supports in accordance with usual practice. Typical supports for photographic elements of the invention include cellulose nitrate film, cellulose acetate film, polyvinyl acetal film, polystyrene film, polyethyleneterephthalate film and related films of resinous materials, as well as glass, paper, metals, wood and others.

Several nitramino and nitrosamino derivatives of the invention were prepared and incorporated into photographic silver halide emulsions at varying concentrations and thereafter tested an antifoggants. The structural formulas of these prepared addenda of the invention are lettered and listed below, the letters given the addenda below being used for purposes of convenience of reference to indicate these addenda in the tables and examples hereinafter.

Compound A:

N -nitro-pto1uenesulphonamide I| I O 2 2N I C-NHNOz C r-N 1-nitr0-2-nitramino-M-imidazoline Compound C:

Compound B:

CH SCN I l lNHNO S 3 methylthio-5-nitrosamino-1,2,4-thiadiazole Compound D:

CH O-N l (J-NHNOz S 3-methyl5-nitramino-1,2,4-thiadiaz0le Compound E:

6-methy14-nitramino'-1,3,3a,7-tetrazaindene Compound F:

C HaC-N N lNHNOz 3-methyl-5-nitramino-1,2,4-triazole Compound G:

C HN I I NHNO 2 5-nitramino-1,2,4-thiadiaz0le Compound H:

N H CH,('l-NHNH-l-NHNO2 1acetamid0-S-nitroguanidine Compound I NH NH2-( lNHNH 1NHN0a 1-carbamoyll-nitroaminoguanidine Compound K:

C HN lH )NHN O2 2-nitramino thiazole Compound L:

4-11ydroxy-6-methyl-2-nitramino1,3,3a,7-tetrazaindene 4-hydroxy-6-methyl-2-nitraminopyrimidine 7 Compound N:

OH (ISO2NHNO2 l\H-N 3- (N-nitrosulphamoyl) -1,2,4-t1-iaz01e EXAMPLE 1 Typical stabilizers of the invention were incorporated into high speed negative-type gelatino-bromoiodide emulsions which were sulphur and gold sensitized and panchromatically sensitized with a cyanine dye. The silver halide comprised 6.2% by weight of the prepared photographic emulsions and was 95% by weight silver bromide and 5% by weight silver iodide. The emulsions were coated on cellulose acetate film supports. The prepared photographic elements were then incubated for 3 days at 120 F. and 94% relative humidity and for 7 days at 120 F. and 42% relative humidity, and then exposed in the form of film strips in an Eastman Type Ib sensitometer, developed for five minutes at 68 F., and then fixed, washed and dried in the usual manner. Test samples were also exposed directly after coating in the sensitometer for purposes of comparison. The developer had the following formula:

G. N-methyl-p-aminophenol sulfate 2.2 Hydroquinone 8.8 Sodium sulfite 72.0 Sodium carbonate 130.0 Potassium bromide 4.0

Water to make one liter.

The results of the sensitometric tests are summarized by the data set out in Table A below with respect to the relative speed and fog for the various samples. In Table A the speeds indicated are a function of the exposure necessary to give a density of 0.2 above background fog, the initial control speed being taken as 100 in each case; and the concentrations of addenda are indicated as grams of addenda per mole of silver halide.

Table A 3 days 7 days Cone. of Initial test 120 F.. 120 F., Addenda addenda 94% R11. 42% R11.

(grams/ mole of AgX) Speed Fog Speed Fog Speed Fog 0 100 11 70 2 1 0. 9 100 09 (i0 19 0 100 15 40 40 0. 9 105 12 65 25 0 100 15 65 36 0. 45 105 11 85 20 0. 9 100 11 65 15 1. 35 85 11 85 13 0 100 13 65 40 0. 9 100 12 70 31 0 100 17 70 80 0. 9 115 13 100 36 0 100 16 45 38 0. 9 105 13 65 22 0 100 00 65 23 0. 9 105 70 21 Control 0 100 16 45 39 Compound G 4. 5 90 14 65 18 0 100 13 50 17 0. 9 110 ll 75 40 0 100 18 65 67 1. 5 100 13 80 51 0 100 21 80 34 0. 9 110 19 90 23 1. 8 100 21 80 22 0 100 21 80 34 0. 9 110 95 28 0 100 21 BO 34 Compound N O. 9 110 18 100 26 D0 1. 8 100 .17 100 23 EXAMPLE 2 Samples of the photographic emulsion described in Example 1 were tested with antifoggants of the invention as described in Example 1 except that the samples were stored for 3 and 6 month periods under ambient conditions of'about'68 F. and 50% relative humidity. The results of the sensitometric tests are summarized by the data set out in Table B below.

Table B Cone. of Initial 3 Months 6 Months addenda test after coating aiter coating Addenda (grarus/ mole of .AgX) Speed Fog Speed Fog Speed Fog 0 100 .17 9O .24 .28 0. 9 115 13 105 16 100 18 0 100 16 85 14 80 18 4. 5 14 11 85 1O 0 18 9O 7 .21 80 .27 4. 5 100 13 100 17 90 23 0 100 16 85 18 80 19 0.9 15 100 16 95 .16 01 0 100 .23 80 .25 70 .27 Compound K 0. 9 18 100 16 90 18 Do. 2. 25 110 .18 100 17 100 17 As can be observed from the data set out in Tables A and B above, the nitramino and nitrosarnino compounds of the invention impart substantial antifoggant or stabilizing properties to photographic silver halide emulsions. Also to be noted is that there is no accompanying substantial loss of speed with the improved stability in the present instance, and which loss of speed characterizes many stabilizers. In many instances with the subject stabilizers there is actually an increase in speed over the control sample containing no addenda.

The addenda of the invention can be readily prepared. Compound A was prepared by the method of Gillibrand and Lamberton, J.C.S., 1949, 1883. Compound B was prepared by the method of McKay and Wright, J.A.C.S., 70, 3990 (1948). Compound C was prepared by the method of Goerdeler and Linden, Ber. 89, 2742 (1956). Compounds F and H were prepared by the method of Henry, J.A.C.S. 72, 5343 (1950). Compound K was prepared by the method of Dickey, Towne and Wright, J. Org. Chem. 20, 499 (1955). The other addenda specifically referred to above were prepared by the methods described below.

Compound D.-A solution of 2.3 g. (.02 mole) of 5- amino-B-methyl-1,2,4-thiadiazole in 10 g. of 98% sulphuric acid was treated with 1.76 mls. (.04 mole) of 95% nitric acid at 0 C. and the mixture allowed to rise to room temperature. After 1% hours at room temperature the mixture was poured onto ice and the colorless precipitate filtered and washed with water. One crystallization from water gave 2.3 g. pure material, M.P. 210 C. with decomposition.

Compound E.Amino 6 methyl 1,3,3a,7 tetrazaindene (3.0 g., .02 mole) was added at 0 C. to a mixture of 15 mls. of acetic anhydride and 0.84 mls. (.02 mole) of 100% nitric acid. To this mixture was gradually added 2.5 g. (0.0185 mole) of zinc chloride dissolved in 10 mls. of acetic anhydride, keeping the temperature at 15-20" C. After a further 45 minutes at 20 C. the mixture was poured into water and filtered. The product was dissolved in sodium bicarbonate, treated with activated charcoal, filtered and acidified to give a colorless material, M.P. 227 C., decomposes. One crystallization from water gave pure material, M.P. 229 C. decomposes.

Compound G.-5 amino 1,2,4 thiadiazole nitrate (6.6 g.) was gradually added, with stirring, to 20 g. of 98% sulphuric acid at 0-40 C. and the mixture allowed to rise to 20 C. After 30 minutes at 20 C. the mixture was poured onto ice and the precipitate collected. The product was crystallized from water, with carbon treatment, to give a colorless material, 2.4 g., M.P. 207-208 C. decomposes.

Compound J.-Semicarbazide hydrochloride (6.25 g.) was dissolved in 54 mls. of 1 N sodium hydroxide and the solution added slowly with stirring, to N-methyl-N- nitroso-N-nitroguanidine (8.2 g.) suspended in 50 mls.

of alcohol. The mixture was stirred for 24 hours at room temperature, cooled in ice and filtered. Crystallization from water gave a colorless product, 3.5 g., M.P. 213 C. decomposes.

Compound L.-2 amino 4 hydroxy 6 methyl- 1,3,3a,7-tetrazaindene (3.3 g., 0.02 mole) was dissolved in 85% sulphuric acid (16 g.) and the solution cooled to C. Absolute nitric acid (1.68 mls., 0.04 mole) was gradually added, with stirring, over 10 minutes, keeping the temperature at 0 C. The temperature was allowed to rise to 25 C. and kept there for 1 hour. The resulting solution was poured on ice and the precipitate collected. The product was crystallized from dilute sodium carbonate to give pure material (2.9 g.) It does not melt.

Compound M.N-itroguanidine (10 g., 0.1 mole) and ethylacetoacetate (13 g., 0.1 mole) were refluxed for 4 hours in absolute alcohol (250 ml.) containing sodium (2.3 g., 0.1 mole). The mixture was cooled and the product filtered. This sodium salt was dissolved in cold water and the trace of unreacted nitroguanidine filtered off. The filtrate was acidified with dilute hydrochloric acid to give the free acid. Two crystallizations from water gave pure material (6 g.), M.P. 248 C. decomposes.

Compound N. 1,2,4-triazole-3-sulphonamide (3 g.) was gradually added, over 10 minutes, to a mixture of 98% sulphuric acid (15 g.) and absolute nitric (3.6 rnls.) at 010 C. The temperature was allowed to rise to C. and kept there for 1 hour. The mixture was then poured on to 32 g. of ice and cooled to 4 C. overnight. The product was filtered off and dissolved in 5 mls. of water. Addition of about 5 mls, of concentrated hydrochloric acid and cooling gave pure material (1.6 g.), M.P. 187 C. decomposes.

The present invention thus provides a new and useful class of photographic silver halide emulsion stabilizer or antifoggant addenda.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A photographic silver halide emulsion containing as an antifoggant a nitrogen-containing compound having a formula selected from the group consisting of and Y-NHNO wherein X is selected from the group consisting of p-toluenesulfonyl, imidazolyl, thiadiazolyl, tetrazaindenyl, triazolyl, thiazolyl, pyrimidinyl and guanidino radicals, and Y is a thiadiazolyl radical.

2. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula X-NHNO wherein X is a p-toluenesulfonyl radical.

3. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula XNHNO wherein X is a imidazolyl group.

4. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula X-NHNO wherein X is a thiadiazolyl group.

5. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula X--NHNO wherein X is a tetrazaindenyl group.

6. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula X-NHNO wherein X is a triazolyl group.

7. A photographic silverhalide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula XNHNO wherein X is a thiazolyl group.

8. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula XNHNO wherein X is a pyrimidinyl group.

9. A photographic silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula X-NHNO wherein X is a guanidino group.

10. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of an antifoggant having the formula X-NHNO wherein X is a thiadiazolyl group.

11. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of 3-methylthio-5-nitrosamino-1,2,4-thiadiazole.

12. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of 1-nitro-2-nitramino-n -imidazoline.

13. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of 3-methyl-5-nitramino-1,2,4-thiadiazole.

14. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of N-nitro-p-toluenesulphonarnide.

15. A photographic gelatino-silver halide emulsion containing about .001 to 10 grams per mole of silver halide of 6-methyl-4-nitramino-1,3,3a,7-tetrazaindene.

16. A photographic gelatino-silver halide emulsion conabout .001 to 10 grams per mole of silver halide of an antifoggant selected from the group consisting of N-nitro-p-toluenesulphonamide, 1-nitro-2-nitram.ino-A -imidazoline, 3-methyl-5-nitramino-1,2,4-thiadiazole. 3methyl-5-nitramino- 1 ,2,4-thiadiazole, 6-methyl-4-nitramino-1,3,3a,7-tetrazaindene, 3-methyl-5-nitramino-1,2,4-triazole, S-nitramino-l,2,4-thiadiazole, 1-acetamido3-nitroguanidine, 1-carbamoyl-4-nitroaminoguanidine, Z-nitramino thiazole, 4 hydroxy-6-methyl-2-nitramino-1,3,3a,7-tetrazaindene, 4-hydroxy-6-methyl-2-nitraminopyrimidene, and 3- (N-nitrosulphamoyl) -1,2,4-triazole.

17. A photographic emulsion support having coated thereon an emulsion as described in claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,901,351 Van Pee et al Aug. 25, 1959 FOREIGN PATENTS 835,047 Great Britain May 18, 1960

Claims (1)

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING AS AN ANTIFOGGANT A NITROGEN-CONTAINING COMPOUND HAVING A FORMULA SELECTED FROM THE GROUP CONSISTING OF