A method of improving the stability of alkaline solutions containing azo dyestuff components of an exclusively phenolic nature

摘要

510,407. Stabilizing solutions of phenols. NAAMLOOZEVENNOOTSCHAP CHEMISCHE FABRIEK L. VAN DER GRINTEN. Nov. 1, 1938, No. 31645. Convention date, Nov. 5, 1937. [Class 2 (iii)] [Also in Group XX] The stability of alkaline solutions containing azo dyestuff components of an exclusively phenolic nature, e.g. diazotype developing solutions, is improved by adding to said solutions, or to the components of which said solutions are prepared, a small quantity of a tin compound which is soluble in said alkaline solutions. Tin compounds specified are stannous and stannic chloride, stannates, stannites, and chlorostannates, and phenols specified are phloroglucinol, resorcinol, and #-naphthol, but hydroquinone (which is not an azo-dye component) and aminophenols (which are not exclusively phenolic) are specifically excluded. The quantity of tin compound should not be more than 1 per cent. of the weight of solution. In an example, 0.1 per.cent. of sodium stannate is added to a diazotype developing solution containing 6 per cent. sodium thiosulphate, 2 per cent. thiourea, 1 per cent. borax, 1.5 per cent. of soda, 2 per cent. of resorcinol.