Verfahren zur Herstellung photographischer Kontraste

737,874. Photographic process. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. Sept. 28, 1951 [Oct. 3, 1950], No. 22669/51. Class 98 (2). A photographic image is produced by physical development of mercury nuclei separated from a mercurous compound introduced into the light-sensitive material before or after exposure by one or more of the molecules or ions CN1, CNS1, NO,', SO 3 11, SO 2 , S 2 O 3 11, NH 3 , organic amines, pyridine, or thiourea or substitution products thereof, which molecules or ions are freed by light exposure from light-sensitive compounds which are themselves unable to free mercury from a mercurous compound and which are light-sensitive cyanhydrins or bisulphite compounds of aromatic aldehydes which may be nitro-substituted in o- or pposition; diazo cyanides; complex cyanides or thiocyanates ; or complex nitro, nitrito-, sulphito-, thiosulphato-, or ammine compounds or organic amino, pyridine, thiourea, or substituted thiourea compounds with at least one central metal ion capable of shifting to a lower oxidation state on exposure to light. Complex compounds of CrIII, FeIII, CoIII, RIII, MoIV, MoV, WVI, and MnIII may be used. In example 1, superficially saponified cellulose acetate film is sensitized with an aqueous solution of [Co(NH 2 .C 2 H 4 .NH 2 ) 2 SO 3 ]Cl and dried. The exposed material is treated with a dilute nitric acid solution of mercurous nitrate, washed, developed in an aqueous solution of metol, citric acid, and silver nitrate. In examples 2 and 3, the procedure is similar, using K 3 Mo (CN) 8 and K[Co(NH 3 ) 2 (NO 2 ) 4 ] respectively. In' example 4, the procedure is also similar, using a superficially saponified ethylcellulose foil sensitized with an alcoholic solution of onitrobenzaldehyde cyanhydrin. The support may also be paper, regenerated cellulose, or textile, and the light-sensitive substance may also be K 4 Mo(CN) 8 , K 4 W(CN) 8 , K 3 Fe(CN) 6 , NaFe(CN) 5 NO, K 3 CO(CN) 6 , K 3 Rh(CNS) 6 , K 3 Cr (CNS) 6 , Na 3 Co(NO 2 ) 6 , LiCo(SO 3 ) 3 , Na[Co(NH 2 C 2 H 4 NH 2 ) 2 (SO 3 ) 2 ], o-nitrobenzyl cyanide, pnitrobenzyl cyanide, p-methoxybenzene diazocyanide, [Co(NH 3 ) 4 {CS(NH) 2 } 2 ]NO 3 , [Co(NH 3 ) 2 {CS(NH 2 ) 2 }Cl 2 ]Cl, and o-nitrobenzaldehyde potassium bisulphite. The material may be physically colour developed as described in Specification 735,424. Specifications 439,005 and 5962/47, 23643/48, and 3140/49 (all as open to inspection under Sect. 91 (4)) also are referred to.