US3208991A - Azo dye developers - Google Patents

Description

United States Patent 3,208,991 AZO DYE DEVELOPERS Elkan R. Blout, Belmont, Milton Green, Newton Center,

Howard G. Rogers, Weston, and Myron S. Simon, N ewton Center, Mass., assignors to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware No Drawing. Filed Sept. 10, 1962, Ser. No. 222,702 6 Claims. (Cl. 260-462) This application is a con-tinuation-in-part of our application Serial -No. 685,081, filed September 20, 1957, now abandoned.

This invention relates to photography and more particularly to products, compositions and processes for the development of photosensitive silver halide elements.

It is one object of the present invention to provide novel processes and compositions for the development of silver halide emulsions, in which novel colored developing agents are used.

Another object is to provide novel processes and compositions for the development of silver halide emulsions, in which the novel developing agent is capable of developing an exposed silver halide emulsion and imparting a reversed or positive colored image of the developed image to a superposed image-receiving material.

A further object is to provide novel silver halide developing agents and novel products, processes and com positions suitable for use in preparing monochromatic and multichromatic photographic images.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the processes involving the sever-a1 steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

The objects of this invention may be accomplished by the use of certain novel dyes which have the ability to develop images present in an exposed silver halide emulsion; thus they may be referred to as dye developers. These novel dyes or dye developers will be further described hereinafter.

ZFor a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

The photographic processes and compositions disclosed herein are particularly useful in the treatment of an exposed silver halide emulsion, whereby a positive dye image may be imparted to another element, herein referred to as an image-carrying or image-receiving element.

US. Patent No. 2,983,606, issued May 9, 1961 to Howard G. Rogers, discloses diffusion transfer processes wherein a photographic negative material, such as a photographic element comprising an exposed silver halide emulsion, is developed in the presence of a dye developer to impart to an image-receiving layer a reversed or positive dye image of the developed image by permeating into said emulsion a suitable liquid processing composition and bringing said emulsion into superposed relationship with an appropriate image-receiving layer. The inventive concepts herein set forth provide novel dye developers for use in such processes.

In carrying out the process of this invention, a photosensitive element containing a silver halide emulsion is exposed and wetted with a liquid processing composition, for example by immersin coating, spraying, flowing, etc., in the dark, and the photosensitive element superposed prior to, during or after wetting, on an image-rereceiving element. In a preferred embodiment, the photosensitive element contains a layer of dye developer, and the liquid processing composition is applied to the photosensitive element in a uniform layer as the photosensitive element is brought into superposed position with an image-receiving element. The liquid processing composition permeates the emulsion to provide a solution of dye developer substantially uniformly distributed therein. As the exposed silver halide emulsion is developed, the oxidation product of the dye developer is immobilized or precipitated in situ with the developed silver, thereby providing an imagewise distribution of unoxidized dye developer dissolved in the liquid processing composition. This immobilization is apparently due, at least in part, to a change in the solubility characteristics of the dye developer upon oxidation, and especially as regards its solubility in alkaline solutions. It may also be due, in

- part, to a tanning effect on the emulsion by the oxidized developing agent. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer. The image-receiving layer receives a depth'wise diffusion, from the emulsion, of unoxidized dye developer, without appreciably disturbing the imagewise distribution thereof, to provide a reversed or positive, colored image of the developed or negative image. The image-receiving element may contain agents adapted to mordant or otherwise fix the difiused, unoxidized dye developer. Imbibition periods of .approximately one minute have been found to give good results, but this contact period may be adjusted where necessary to compensate for variations in temperature or other conditions. The desired positive image is revealed by stripping the image-receiving layer from the silver halide emulsion at the end of the imbibition period.

The dye developers of this invention may be utilized in the photosensitive element, for example in, on or behind the silver halide emulsion, or they may be utilized in the image-receiving element or in the liquid processing composition. In a preferred embodiment, a coating or layer of the dye developer is placed behind the silver halide emulsion, i.e., on the side of the emulsion adapted to be located most distant from the photographed subject when the emulsion is exposed and preferably also adapted to be most distant from the image-receiving iayer when in superposed relationship therewith. Placing the dye developer behind the emulsion layer, as in the preferred embodiment, has the advantage of providing increased contrast in the positive image, and also minimizes any light-filtering action by the colored dye developer. In this preferred embodiment, the layer of dye developer may be applied by using a coating solution containing about 0.5 to 8%, by weight, of the dye developer. Similar concentrations may be used if the dye developer is utilized as a component of the liquid processing composition. In an especially useful mode of disposing the dye developers in the photosensitive elements, the dye developer is dissolved in a water-immiscible solvent and then dispersed in a gelatin coating solution.

The liquid processing composition which is used in the processes herein disclosed comprises at least an aqueous solution of an alkaline compound, for example, diethylamine, sodium hydroxide or sodium carbonate, and may contain the dye developer. In some instances, it may contain an additional silver halide developing agent. If the liquid processing composition is to be applied to the emulsion by being spread thereon, preferably in a relatively thin, uniform layer, it may also include a viscosityincreasing compound constituting film-forming material of the type which, when spread over a water-absorbent base, will form a relatively firm and relatively stable film.

wherein Ar is an aryl nucleus, such as a benzene or naphthalene nucleus; each Z is an alkoxy group, preferably a lower alkoxy group such as methoxy, ethoxy, etc., an alkyl group, preferably a lower alkyl group such as methyl, ethyl, etc., a hydroxyl group, or a halogen group such as chlorine; m is or 1; n is 0 or a positive integer from 1 to 4, inclusive; p is 1 or 2; R is an alkylene group, preferably containing no more than 5 carbon atoms; Y is a p-dihydroxyphenyl or o-dihydroxyphenyl group, and alkyl and halogen substituted derivatives thereof; X and X, are each the radical of a coupling component, which coupling component may-be the same or different. By the expression coupling component, as used in the above formula and hereinafter, is meant a compound capable of being coupled into by a diazonium salt, i.e., an azo coupler.

In a preferred embodiment, the aryl nucleus is a henzene nucleus and p is 1.

As illustrations of suitable azo coupling components or couplers from which X and X may be derived, mention may be made of phenols and aromatic amines having a free position ortho or para to the hydroxyl or amino group, e.g., phenol, anilines, napthols, anthrols, napthyl-amines, etc.; heterocyclic aromatic compounds containing hydroxyl or amino groups, such as pyrazolones or pyrroles; aliphatic or alicyclic activated methylene couplers, i.e., compounds having an aliphatic or alicyclic methylene group activated by two adjacent keto, aldehyde, ester or nitrile groups, which may be the same or different, or a keto, aldehyde, ester or nitrile group in combination with an amide group; e.g., 1,3-diketones or B-ketonic acid arylamides, etc., and substituted derivates thereof. Examples of groups which may 'be' present in such substituted derivatives includealkyl, sulfo, alkoxy, aryl, aryloxy, amino, keto, alkylamino, arylamino, hydroxyl, cyano, alkylamido, arylamido, carbalkoxy, carboxamido, sulfonamido, etc. As used herein with reference to X and X the expression radical of a phenolic coupler is intended to refer to hydroxyphenyl, hydroxynaphthyl, hydroxyanthryl,

etc. radicals, and substituted derivatives thereof; the expression radical of an aromatic amino coupler is intended to refer to aminophenyl, aminonaphthyl, etc. radicals, and substituted derivatives thereof; and the expres:

sions radical of a heterocyclic-aromatic coupler, radical of an aliphatic activated methylene coupler and radi- A cal of an alicyclic activated methylene coupler are to be similarly construed.

- The novel dye developers of this invention may be prepared by diazotizing a compound of the formula:

n YfiR-Ar(N=NXa)mNH;

wherein Y, R, Ar, Z, n, X,,, and m have the samemeaning as above, and coupling diazotized compound (B) intothe desired coupling component providing X As examples of useful intermediates Within the scope of Formula B, mention may be made of the following compounds:

p-(2, li-dlhydroxyphenaeyl) -an1line (2) (I) CH3 2 S-[2, 5-dimethoxy-3- (2", 5"-dimethoxy-3 -alnino-phenylazo)-phenyl]- propionyD-hydroquinone v OH v a-h-(4-amino-phenyl)-butyryl1-hydroquinone I OOH; 2-[13- (2-,5-dimethoxy-B'-amino-phcnyl) -a-methyI-propionyl1-hydroquinone 4 r. V p

I 2-[5-(3',4-dimethoxy-6-aml.no-pheny1)-proplonyl-hydroquinone 9 OH 0on V 0 on,

1130- -ii-on-on, NH, 7

2-[B- (2,5-dimethoxy 3-amino-phenyl) -a-methyl-proplonyll- 6-methyl-hydroquinone (10) OH CH3 l E) (IJHs l 1130- -(i-CHCH3 NH;

| OH 0 CH3 3,6-dimethyl-2-[B- (2,5-dimethoxy-3-amiuo-phenyl)- t-methyl-propiony11-hydroquinone OCHg 0 -ii-onz- 1-amino-4- (2', 5 -dihydroxyphenacyl) -naphtha eue In general, the compounds of Formula B, wherein R is any desired homologue may be prepared by (a) nitrating a compound of the formula:

rib-R-COOH e.g., phenylaoetic acid, naphthylacetic acid, their homologues and their analogues, to form the nitroaryl analogue; (b) forming the acid chloride of the said analogue; (c) foming the hydroquinone derivative by the F-riedel- Crafts reaction; and (d) reducing the nitro group (preferably in an acid medium) to form the compound of Formula B.

The compounds of Formula B wherein m .is 0 may also be prepared according to the procedure disclosed in the -copending application of Elk'an R. Bl-out and Myron S. Simon, Serial No. 165,006, filed January 8, 1962, and which is a continuation-in-part of Serial No. 685,066, filed September 20, 1957, now abandoned. If desired, the hydroxyl groups may be protected during reaction by the use of suitable protective derivatives, e.g., O-acetyl derivatives, according to the procedure disclosed in the aforementioned copending application. However, it is also contemplated to effect diazotization of the compounds of Formula B where the hydroxyl groups are free. Where desired, the monoazo inter-mediates may be employed for further diazotization without removal of the protective groups.

Where desired, the compounds of Formula B may be employed in the form of acid addition salts, e.g., the hydrochloride.

The coupling is generally performed at a pH which is preferably not greater than about 9. The hydroxy groups of Y may be protected during diazotization and coupling, as by the use of O-acetyl derivatives as mentioned above.

By the use of two mols of the diazonium salt to each mol of the coupling component, one may couple twice into certain of the coupling components which provide the residue X as, for example, hydroxy and amino aromatic compounds which have two directing groups and two free coupling positions as, for example, 1,5-dihydroxynaphthalene. It may be noted that such bis coupling may give rise to a mixture of dye developers, and such mixtures may be used in the processes of this invention.

Where the coupling component is a phenolic coupler, and particularly a naphthol, it has been found that coupling ortho to the hydroxyl group gives a dye developer of superior color properties. It has also been found that such ortho-coupled dye developers exhibit essentially no pH sensitivity over a fairly wide range on either side of neutral.

As examples of suitable dye developers within the scope of this invention, mention may be made of the following:

OH. I

4-[p- (2, 5-dihydroxyphenacyl) -phenylaz0]-3- (N-n-hexylcarbamyl) -1- phenyl-5-pyrazolone OH OH,

2 [p-(2, 5-dihydroxyphenacyl) -phenylazol-t-methoxy-l-naphthol The coupling component employed to provide the residue X is preferably a coupler containing a diazotizable amino group. It is to be understood, however, that one may employ a coupler having a group convertible to adiazotizable amino group, e.g., a nitro group. The diazotizable amino group may be on a nucleus other than the one substituted by the azo grouping.

7 As examples of additional coupling components which may b'e used to provide X mention may be made of:

4-benzyl-l-naphthol 4-methyl-1-naphthol 4-methoxy-a-naphthylamine 4-acetamino-a-naphthylamine Phenol Aniline 1,5 -naphthalenediamine p-Cresol l-hydroxyanthracene 1-hydroxy-2-naphthanilide Diketohydrindene Malononitrile Acetoacetanilide group. The presence of the acyl group lowers the developing potential of the dye developer and the resulting dye developer, inthe absence of, an auxiliary or accelerating developing agent, is relatively unreactive, and thereby results in a useful synergistic developing agent which is ssentially unreactive during storage, e.g., when the dye developer is disposed in the photo-sensitive element prior to exposure of said element.

The following examples of the preparation of dye developers within the scope of this invention by coupling compounds within Formula B are given for purposes of illustration only.

Example 1 (0.01 mol) of 2-['y-(2',5'-dinrethoxy-3'-amino-phenyl)- propionyl]-hydroquinone hydrochloride was dissolved in 200 cc. of 6 N hydrochloric acid and a solution of (0.01 mol) of sodium nitrite in 15 cc. of Water. The mixture was stirred for approximately 15 minutes while being cooled to about C., filtered through Celit'e, allowed to stand for approximately 30 minutes, and added to a solu tion of (0.0086 mol) of 4-methoxy-1-naphthol in 100 cc. of water and 120 cc. of pyridine. 20% sodium carbonate solution was added intermittently to retain the pH at 7 to 8. After approximately one hour the slurry was filtered, washed with aqueous acetic acid, then washed with water and purified by precipitation from methyl c'ellosolve with 1% hydrochloric acid solution. The resultant 4 methoxy 2 (2',5' dimethoxy 3'- [2"-(2"',5"'-dihydroxybenzoyl) ethyl] phenylazo)-l-naphthol, [Formula 15], spectral absorption curve shows a A at 530 m in acetone, e=19,600.

Example 2 Example 3 2- ('y-[2',5-dimethoxy-3'-(2",5"-dimethoxy 3"-aminophenylazo) -phenyl] -propionyl) hydroquinone hydrochloride was diazotized in a manner similar to that described in Example 1 and coupled with 4-methoxy-l-naphthol. The resultant product was 4-methoxy-2-[2',5'-dimethoxy- 4 (2",5"-dimethoxy 3"-[2"'-(2",5"" dihydnoxyben- 8 zoyl) -'ethyl] -phenylazo) -phenylazo] l-naphth-ol, [Formula 17]. The spectral absorption curve showed a Amax, at 590 m in methyl cellosolve, e=14,400.

In the same manner as described in the foregoing examples, 4-[p-(Z',5-dihydroxyphenacyD-phenylazo] 3-(N- n-hexylcarbamyD-l-phenyl-S-pyrazolone [Formula 13] and 2- [p-Z, 5 -dimethoxyphenacyl)-phenylazo] -4-me'thoxyl-naphthol [Formula 1 4] were prepared by coupling diazotized p-(Z,5-dihydroxyphenacylyan-iline with the azo coupl'er moiety of the compound.

Example 4 A photosensitive element was prepared by coating a gelatin-coated film base with a solution containing 3% of 4-methoxy-2 (2,5 dimethoxy 3' [2 (2",5"'-dihydroxybenzoyl)-ethyl] phenylazo) l-naphthol [Formula 15 as prepared in Example 1] in a 4% solution of cellulose acetate hydrogen phthalate in a 50:50 mixture, by volume, of acetone and tetrahydrofuran. After this coating had dried, a silver iodobromide emulsion was applied. This photosensitive element was exposed and processed by spreading an aqueous liquid processing composition comprising:

, Percent Sodium carboxymethyl cellulose 6.0 1-phenyl-3-pyrazolidone 0.2 Sodium hydroxide 5.0 Potassium bromide 0.5

Example 5 A photosensitive element was prepared similar to that described in Example 4 using 3% of l-phenyl-B-methyl- 4-(2,5'-dimethoxy-3 [2" (2.",5"' dihydroxybenzoyl)- ethyl]-phenylazo)-5-pyrazolone, [Formula 16 as prepared in Example 2]. This photosensitive element was exposed and processed by spreading an aqueous liquid processing composition comprising:

- Percent Sodium carboxymethyl cellulose 4.5 1-phenyl-3-pyrazolidone 0.2 Sodium hydroxide 3.0 Potassium bromide 0.2 between said photosensitive element and an image-receiving element as said elements were brought into superposed relationship. The image-receiving element comprised a cellulose-coated baryta paper which had been coated with a solution comprising 10% Nylon Type F8 (trade name for N-methoxymethyl polyhexamethylene adipamide) in aqueous ethanol. After an imbibition period of approximately one minute, vthe image-receiving element was separated and contained a yellow positive dye image of the photographedsubject.

Example 6 A photosensitive element was prepared similar to that described in Example 4 using 3% of 4-methoxy-2-[2',5- dimethoXy-4-(2",5" dimethoxy 3" [2"-(2"",5""-dihydroxybenzoyl -ethyl] phenylazo) -phenylazo] -1-naphthol, [Formula 17 as prepared in Example 3]. Exposure and processing with a liquid processing composition and image-receiving element similar to those described in Exangple 4 gave a tan positive dye image of the photographed su ject.

9 Example 7 A photosensitive element was prepared similar to that described in Example 4 using 3% of 4-[p-(2,5-dihydroxyphenacyl)-phenylazo] 3 (N-n-hexylcarbamyl)-1- phenyl-S-pyrazolone [Formula 13]. Exposure and processing with a liquid processing composition and imagereceiving element similar to those described in Example 4 gave a yellow positive dye image.

Example 8 A photosensitive element was prepared similar to that described in Example 4 using 3% of 2-[p-(2',5-dihydroxyphenacyl)-phenylazo] 4-methoxy-1-naphthol [Formula 14]. Exposure and processing with a liquid processing composition and image-receiving element similar to those described in Example 4 gave a magenta positive dye image.

Repeating the procedures of Example 4, 5 and 6 without the auxiliary developing agent results in positive dye images which exhibit poor contrast and colored highlights, thus indicating that the dye developer in the exposed areas of the light-sensitive element is not oxidized rapidly enough to control the transfer of said dye developer from the exposed areas to a superposed image-receiving layer.

The dye developers of this invention are also useful in integral multilayer photosensitive elements for use in multicolor diffusion transfer processes. As an example of such photosensitive elements, mention may be made of the photosensitive elements disclosed and claimed in the copending US. application of Edwin H. Land and Howard G. Rogers, Serial No. 565,135, filed February 13, 1956, wherein at least two selectively sensitized photosensitive strata are superposed on a single support and are processed, simultaneously and without separation, with a single common image-receiving element. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer. In one of the preferred embodiments of photosensitive elements of this type, the dye developers are disposed in separate alkali-permeable layers behind the photosensitive silver halide emulsion stratum with which they are associated.

The photosensitive elements within the scope of this invention may be used in roll film units which contain a plurality of photosensitive frames. The photosensitive elements of this invention are especially useful in composite roll film intended for use in a Polaroid Land Camera or a similar camera structure such, for example, as the camera forming the subject matter of US. Patent No. 2,435,717, issued to Edwin H. Land on February 10, 1948. In general, such composite roll films comprise a photosensitive roll, a roll of image-receiving material and a plurality of pods containing an aqueous alkaline processing solution. The rolls and pods are so associated with each other that, upon processing, the photosensitive element may be superposed on the image-receiving element and the pods may be ruptured to spread the aqueous alkaline processing solution between the superposed elements. The nature and construction of the pods used in such units are well known to the art. See, for example, US. Patents Nos. 2,543,181 and 2,634,886, issued to Edwin H. Land.

It will be noted that the liquid processing composition may contain one or more auxiliary or accelerating silver halide developing agents, such as p-methylaminophenol (Metol); 2,4-diaminophenol (Amidol); benzylaminophenol; hydroquinone; a substituted hydroquinone such as toluhydroquinone, phenylhydroquinone, or 4 methylphenylhydroquinone; or a 3-pyrazolidone such as 1- phenyl-3-pyrazolidone. These silver halide developing agents are substantially colorless, at least in their unoxidized form. It is possible that some of the dye developer oxidized in exposed areas may be oxidized by an energy transfer reaction with oxidized auxiliary developing agent.

In addition, development may be effected in the presence of an onium compound, particularly a quaternary ammonium compound, in accordance with the processes disclosed and claimed in the copending application of Milton Green and Howard G. Rogers, Serial No. 50,851, filed August 22, 1960.

The dye developers of this invention may be used also in conventional photographic processes, such as tray or tank development of conventional photosensitive films, plates or papers to obtain black-and-white, monochromatic or toned prints or negatives. By way of example, a developer composition suitable for such use may comprise an aqueous solution of approximately 1-2% of the dye developer, 1% sodium hydroxide, 2% sodium sulfite and 0.05% potassium bromide. After development is completed, any unreacted dye developer is washed out of the photosensitive element, preferably with an alkaline washing medium or other medium in which the unreacted dye developer is soluble. The expression toned is used to designate photographic images wherein the silver is retained with the precipitated dye, whereas monochromatic is intended to designate dye images free of silver.

It should be noted that the dye developers of this medium are self-sufficient to provide the desired color image and do not depend upon coupling reactions to produce the desired color. They thus provide a complete departure from conventional photographic color processes in which the color is produced by a coupling reaction between a color former or coupler and the oxidized developing agent, as well as so-called auto-coupling processes in which color is obtained by a reaction of the oxidized developing agent with unoxidized developing agent.

It will be apparent that, by appropriate selection of the image-receiving element from among suitable known opaque and transparent materials, it is possible to obtain either a colored positive reflection print or a colored positive transparency. Likewise, the inventive concepts herein set forth are adaptable for multicolor work by the use of special photographic materials, for example, film materials of the type containing two or more photosensitized elements associated with an appropriate number of imagereceiving elements and adapted to be treated with one or more liquid processing compositions, appropriate dye developers suitable to impart the desired subtractive colors being incorporated in the photosensitized elements or in the liquid processing compositions. Examples of such photographic materials are disclosed in US. Patent No. 2,647,049 to Edwin H. Land.

As examples of useful image-receiving materials, mention may be made of nylon, e.g., N-methoxymethyl-polyhexamethylene adipamide, polyvinyl alcohol, and gelatin, particularly polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine. The image-receiving element also may contain a development restrainer, e.g., 1-phenyl-S-mercaptotetrazole, as disclosed in the copending application of Howard G. Rogers and Harriet W. Lutes, Serial No. 50,849, filed August 22, 1960.

The dye developers herein set forth are also useful in the formation of colored images in accordance with the photographic products and processes described and claimed in US. Patent No. 2,968,554, issued to Edwin H. Land on January 17, 1961.

The novel compounds herein disclosed are also suitable for use as dyes for textile fibres, such as nylon.

In the preceding portions of the specification, the expression color has been frequently used. This expression is intended to include the use of a plurality of colors to obtain black.

Our copending US. application, Serial No. 222,656, filed concurrently herewith and now Patent No. 3,142,- 5 65, claims the photographic utilization of the novel compounds of the present invention.

wherein Ar is an arylene nucleus selected from the group consisting of phenylene and naphthalene nuclei; Z is alkoxy; m is selected from the group consisting of 0 and 1;

n is selected from the group consisting of 0 and the positive integers from 1 to 2, inclusive; R is an alkylene group; Y is selected from the group consisting of p-dihydroxyphenyl, and alkyl and chlorine substituted derivatives thereof; X is the radical of a benzene azo dye coupler, each of said N :N groups being linked to a nuclear carbon atom of said benzene coupler; and X, is the radical of an azo dye coupler linked to said free -N:N group.

'n-hexylcarbamyl 1 -pheny1-5 -pyrazo1one.

3. 2 [p (2,5' dihydr'oxyph'enacyl) phenylazo] 4 methoxy-l-naphthol. 4. 4 methoxy 2 (2',5' dimethoxy 3'-[2"-(2"',5'- dihydroxybenzoyl -ethyl1 -pheny1azo -1-naphthol. 5. l phenyl 3 methyl 4 (2',5' dimethoxy-3'-[2"- 2",5 '-dihydroxybe1'1zoyl) ethyl] phenylazo)-5-pyrazolone.

6. 4-methoxy-2- [2",5'-'-dimethoxy-4-(2",5"-dimethoxy- 3"-[2' (2"",5"" -'dihydroxybenzoyl) ethyl] phenylazo) -phenylazo]-1-naphthol. 1

Venkataraman: The Chem. of Syn. Dyes, vol. 1, Academic Press Inc., New York, 1952, pp. 358 and 359.

CHARLES B. PARKER, Primary Examiner.

Claims (1)

1. A COMPOUND OF THE FORMULA: