226 PHOTOGRAPHIC FACTS AND FORMULAS 
Glacial acetic acid 100 g 768 gr. 
Water 1000 ccm 16 oz. 
C. Potassium ferricyanide 100 g 768 gr. 
Water 1000 ccm 16 oz. 
D. Ferric chloride V/3\¢ 13.4 gr. 
Glacial acetic acid 10 ccm 77 min. 
Water 1000 ccm 16 oz. 
To make A, dissolve the lead salt in the acid and water, add 
the iron, shake well, and filter. Blue-green tones are obtained 
by immersion of the prints for 5 minutes in a 2 per cent 
solution of glacial acetic acid and then in the following for 
6 minutes: 
A solution 100 ccm 1 oz. 
C solution 100 ccm 1 oz. 
Water 1000 ccm 10 oz. 
Again immerse in the dilute acetic acid bath for a short time, 
wash well, transfer to a 0.5 per cent solution of citric acid, 
and wash for an hour. Then rub the surface gently with a 
pad of absorbent cotton, and immerse in: 
Potassium chromate 5tol0s. 38 to 77a 
Water 1000 ccm 16 oz. 
The colour turns brownish-green; wash the prints, immerse | 
in the citric acid solution, as above, and wash for a short 
time. Bright green tones are obtained by preliminary treat- 
ment with an acetic acid bath and immersion in: 
A solution 80 ccm 614 min. 
B solution 20 ccm 154 min. 
C solution 100 ccm 768 min. 
Water 1000 ccm 16 oz. 
Then the prints must be treated with the acetic acid, chromate 
and citric acid baths. Pure green tones are obtained by 
treating the prints to a preliminary acid bath, then im- 
mersing in: 
