220 PHOTOGRAPHIC FACTS AND FORMULAS 
Rochelle salts 70 ccm 490 min. 
Tartaric acid 100 ccm 700 min. 
Potassium ferricyanide 20 ccm 140 min. 
Water 1000 ccm 16 oz. 
This gives rich brown tones. 
Uranium nitrate 50 ccm 350 min. 
Rochelle salts 50 ccm 350 min. 
Ammonia alum, sat. sol. 100 ccm 700 min. 
Tartaric acid 50 ccm 350 min. 
Potassium ferricyanide 20 ccm 140 min. 
Water 1000 ccm 16 oz. 
This gives reddish-brown tones. 
A simpler formula is: 
A. Uranium nitrate 5g 38 gr. 
Water 500 ccm 8 oz. 
B. Potassium ferricyanide 5g 38 gr. 
Glacial acetic acid 14 ccm 96 min. 
Water 500 ccm 8 oz. 
Mix just before use. Or the prints may be immersed in 
B until bleached, well washed, and then soaked in A until the 
desired colour is obtained. In this last formula, the salts are 
dissolved as given; that is, 10 per cent solutions are not used. 
Olive green tones (Namias). Tone the prints in the usual 
uranium bath, then wash, and immerse in: 
Ferric chloride 5g 38:5 BE, 
Hydrochloric acid 10 ccm 77 min. 
Water | 1000 ccm 16 oz. 
Fix in the acid hypo-sodium acetate bath. 
IRON oR CyANOTYPE Toninc.—In this process the colour 
is dependent on the deposition of Prussian blue on the image, 
and this is soluble in alkalis; therefore, long washing in 
ordinary water is inadvisable. 
Immerse the prints in a 5 per cent solution of potassium 
