By weight


Pyrogallol......... 0.3 parts

Sodium bisulphite .. 1.2 parts

Sodium carbonate .. 1.2 parts


Eikonogen......... 1.1 parts

Sodium sulphite.. .. 2.4 parts

Potassium carbonate 1.5 parts


Hydroquinone..... 0.6 parts

Sodium sulphite.. .. 3.4 parts

Potassium bromide. 0.3 parts

Sodium carbonate .. 7.0 parts

These three formulas each yield one powder. The powders should be put up in oiled paper, and carefully inclosed, besides, in a wrapper of black paper. For use, one powder is dissolved in about 60 parts of distilled water.