512,559. Colour photography. KODAK, Ltd. Dec. 3, 1937, No. 33492. Convention date, Dec. 3, 1936. Addition to 503,826. [Class 98 (ii)] In the three-colour element claimed in the parent Specification a coupling component is employed comprising a dyestuff derivative, which is colourless or yellow or of a colour different from that of the dyestuff, from which the whole. radical containing the coupling function can be split off, leaving either the parent dyestuff or a leuco form immediately re-oxidizable thereto or a generator like indoxyl giving the parent dyestuff directly by oxidation. The dye stuff may be formed either by splitting, by hydrolysis or oxidation or both or reduction, the indophenol, indamine or azomethine formed by coupling development and removing the uncoupled residue or by splitting the uncoupled residue and removing the coupled product. The unwanted coupling component may be removed by forming an alkali metal salt or by coupling with a developer or a diazo compound containing solubilizing groups such as carboxylic or sulphonic acid or halogen or hydroxyl. A coupled product soluble in the first developer may be produced and the residual coupling component split by oxidation. The residual component may be converted to an alkali-stable compound by coupling either with the oxidation product of p-aminodimethyl aniline or with p-nitrosodimethylaniline or with a diazo compound forming a o-azo dye. Coupling development may be preceded by an initial black and white development in neutral or weakly acid solution. Negatives obtained on three-layer material may be printed on to similarly-processed three-layer material. Leuco derivatives may be simultaneously oxidised by oxidative splitting. The three-layer material may be hardened and processed with moderate warming. Emulsions with three different binders such as cellulose acetate-nitrate, cellulose acetate and cellulose ether may be used. The use of. collodion, agar-agar and polyvinyl acetate as binders is referred to. The layers may be kept permeable by coating with dextrine, gum arabic starch-sugar, or gelatine or by softening with alcohol. Coloured coupling components can be used in emulsions which only require transparency to the particular colour. Components containing sulphonic or carboxylic acid groups may be prepared by the use of salicylic sulphonic acid chloride, a-naphthol-4-sulphonic acid chloride or alpha-naphthol-2-carboxylic-acid-chloride Salts formed by the components with quinine, cinchonine or dicinchonine may be employed. Coupling components split by hydrolysis include (a) ethers of reduced indigoid and lignoid vat dyes and of leuco -indophenols and leucoindamines and (b) esters of leuco dyes. Components split by oxidation include (a) carbamic acid derivatives, (b) dibasic acid derivatives in which, for example, one acid group is reacted, usually as an acid chloride, with the leuco dye and the other acid group is reacted with an aminophenol or amino-alpha-naphthol, (c) monobasic acid derivatives, particularly amino- or hydroxyacid derivatives such as glycollic or aminoacetic acid derivatives of thioindigo white, (d) other phenolic or naphtholic coupling components derived from reduced vat dyes, (e) derivatives having an acid methylene coupling function such as cyanacetyl derivatives of leuco-vat dyes, and (f) phosphoric acid derivatives. Components derived from generators of vat dyes, and from meso-derivatives of anthroquinone dyes, and also those comprising oxidation-split acyl derivatives of leuco non-vat dyes, those comprising diazoamino and azo compounds, those comprising acyliminoquinones, those comprising anils, those comprising splitting derivatives of non-reduced dyes such as N-acyl derivatives of indigo, and those comprising derivatives of di- and tri-phenylmethane dyes such as are obtained by reacting the carbinol group with salicylic .acid chloride. The following components are specified as suitable for yellow images : the product of the reaction of 2-acetylaminoanthrahydroquinone with chloracetic ester followed by reaction with amino-alpha-naphthol, the product of the reaction of #-tetrahydroflavanthrene with chloracetic acid followed by conversion to the acid chloride and reaction with aminoa naphthol, 1.5 - dichlor - 2 - acetylamino- 9 - mhydroxyphenylaminoanthrone, the reaction product of 2-acetylamino-anthranol and salicylaldehyde, the product of coupling 2-acetylamino-anthranol and 5-diazo-alpha-naphthol and the product of reaction of 2-acetylaminoanthrahydroquinone and urea chloride followed by reaction with salicyclic acid chloride. The following components are specified as suitable for red or purple images : thioindigo white esterfied with phenol-o-sulphonic acid chloride, the product of reaction of thioindigo white with chlormethanesulphonic acid chloride followed by reaction with amino-alpha-naphthol, the product of reaction of 6:6<1>-dichlorindigo white with urea chloride followed by reaction with salicylic acid chloride, the product of reaction of thioindigo white with salicylylaminoacetyl chloride, and the reaction product of 6:6'-dichlorindigo with salicylic acid chloride. The following components are specified as suitable for blue and blue-green images; the reaction product of salicylic acid chloride and indigo white, the product of reaction of chloracetic acid ester and indigo white followed by reaction with amino-alpha naphthol, the condensation product of isatin and m-aminophenol, and the reaction product of indigo with salicylic acid chloride. Specifications 248,802, 256,775, 263,898, 317,428, 324,119, 331,842, 333,506, [all in Class 2 (iii)], 349,983, 372,355, 377,278, 401,643, [all in Group IV], 498,663, 503,752, 503,824 and 503,827 are referred to. The Specification as open to inspection under Sect. 91 comprises also the subject-matter of Specification 512,752 and also the use of the components in processes in which the dye-image is produced directly by oxidation and in which coupling development is not employed. This subject-matter does not appear in the Specification as accepted.