Pyrocatechin-phosphate Developer.—
| Solution A |
|---|
| Crystallized sulphite of soda | 386 grains |
| Pyrocatechin | 77 grains |
| Water | 8 ounces |
| Solution B |
|---|
| Ordinary crystal phosphate of sodium | 725 grains |
| Caustic soda (purified in sticks) | 77 grains |
| Water | 8 ounces |
Mix 1 part of A with 1 part of B and from 1 to 3 parts of water. If the exposure is not absolutely normal we recommend to add to the above developer a few drops of a solution of bromide of potassium (1.10).
Pyrocatechin Developer
| Sulphite of soda crystallized | 25 1/2 drachms |
| Caustic soda (purified in sticks) | 3 1/2 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 grains |
| Water | 2 5/8 ounces |
| Caustic potash (purified in sticks) | 108 grains |
| Pyrocatechin | 108 grains |
Mix for a formally fixing plate of 5 x 7 inches.
| Developer | 3 drachms |
| Fixing soda solution (1:5) | 5 1/2 drachms |
| Water | 1 ounce |