By weight

I

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

Sodium bisulphite .. 1.2 parts

Sodium carbonate .. 1.2 parts

II

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

Sodium sulphite.. .. 2.4 parts

Potassium carbonate 1.5 parts

III

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.