DEVELOPERS 111 
Sodium sulphite, dry l2¢g 92 gr. 
Water 1000 ccm 16 oz. 
Mix just before use 12 parts with 1 part acetone. 
PyYROGALLOL.—Pyro-ammonia was once the favorite de- 
veloper, but is rarely used now on account of its variability, 
due to the evaporation of the ammonia: 
A. Sodium sulphite, dry 50 g 384 gr. 
Sulphuric acid 6 drops 3 drops 
Pyrogallol : 14g 107.5 gr. 
Water 500 ccm 8 oz. 
B. Potassium bromide 10 per cent solution 
C. Ammonia, sp. gr. 0.91 200 ccm 4 oz. 
Water 1000 ccm 20 oz. 
For use mix 5 parts A, 1 part B, 5 parts C, and 50 parts water. 
Pyro-glycerine (Edwards ).— 
A. Pyrogallol 40 g 1 oz. 
Glycerine 40 ccm 1 oz. 
Denatured alcohol 
(methylated spirit) 250 ccm 6% oz. 
B. Potassium bromide I5¢ 65 gr. 
Ammonia 40 ccm 1 oz. 
Glycerine 40 ccm 1 oz. 
Water 250 ccm 6% oz. 
For use mix 1 part A, 1 part B, and 30 parts water. 
For great contrasts, suitable for black and white line work 
or photomechanical or process plates (Mawson) : 
A. Pyrogallol LS} 54 gr. 
Ammonium bromide 7g 54 gr. 
Potassium metabisulphite 7g 54 gr. 
Water 1000 ccm 16 oz. 
B. Ammonia, sp. gr. 0.91 21 ccm 160 min. 
Water 1000 ccm 16 oz. 
For use, mix in equal volumes. 
