Dissolve in the following range: Sulphite of soda crystallized.......... 25.5 drachms

Caustic soda (purified in sticks) .... 3.5 drachms

Distilled water..... 14 ounces

Pyrocatechin..... .. 308 grains

The pyrocatechin must not be added until the sulphite and caustic soda are entirely dissolved. For use the concentrated developer is to be diluted with from 10 to 20 times as much water. The normal proportion is 1 part of developer in 15 parts of water.

Vogel's Pyrocatechin Combined Developer and Fixing Solution

Sulphite of soda crystallized..... 468 grain?

Water............ 2| ounces

Caustic potash (purified in sticks)......... 108 grains

Pyrocatechin...... 108 grains

Mix for a formally fixing plate of 5x7 inches.

Developer......... 3 drachms

Fixing soda solution (1:5)........... 5.5 drachms

Water............. 1 ounce

The process of developing and fixing with this solution is accomplished in a few minutes. The picture first appears usually, strengthens very quickly, and shortly after the fixing is entirely done.

Ellon's Pyrocatechin Developer

Pyrocatechin, 2 per cent solution (2 grams pyrocatechin in 100 cubic centimeters of water).

Carbonate of potassium, 10 per cent solution (10 grams carbonate in 100 cubic centimeters of water).

For use take equal parts and add water as desired.

Imperial Standard Pyro Developer

I

Metabisulphite of potassium...... 120 grains

Pyrogallic acid. ... 55 grains Bromide of potassium ........... 20 grains

Metol............ 45 grains

Water............ 20 ounces

II

Carbonate of soda. 4 ounces

Water............ 20 ounces

For use mix equal parts I and II.

Bardwell's Pyro-Acetone Developer

Water.'............ 4 ounces

Sulphite of sodium (saturated solution) ............ 4 drachms

Acetone........... 2 drachms

Pyro.............. 10 grams