THE IRON PROCESSES 271 
| Water 1000 ccm 8 oz. 
Wash the prints well and fix in: 
Hypo 50 g 1 oz. 
Ammonia 12.5.cem 120 min. 
Water 1000 ccm 20 oz. 
Thomson's formulas.— 
Ferric oxalate 150 ¢ 75 gr. 
Ferric ammonio-citrate, brown 20g 10 gr. 
@upric chloride’ |. 18¢ 9 gr. 
Gum arabic 20 g 10 gr. 
Water 1000 ccm 1 oz. 
Dissolve the ferric oxalate in warm water and allow to stand 
all night; then add the other ingredients, and filter. The 
solution will not be clear. Print until the deepest shadows 
are well visible. The developer is composed of equal parts 
of a 5.2 per cent solution of Rochelle salts and a 9.4 per cent 
solution of borax with the addition of 0.02 to 0.8 per cent 
potassium bichromate, which keeps the whites pure and acts 
as a restrainer. The prints should be left in the developer 
for 30 minutes, well rinsed, then fixed in: 
Hypo $1.25 ¢ 240 gr. 
Ammonia 7.8ccm 60 min. 
Water 1000 ccm 16 oz. 
Wash for 30 minutes. 
Thomson's later formulas.— 
1. Ferric ammonio-citrate, brown 20¢ 10 gr. 
Ferric oxalate 66 ¢ Saar, 
Potassium oxalate 74 ¢ O7 er. 
Cupric chloride fie 6 gr. 
Gum arabic 20g 10 gr. 
Potassium bichromate 
sol., 1:48 2tol0ccm 1to5 drops 
Water 1000 ccm 1 oz. 
