TONING BROMIDE PRINTS P42 
Cupric sulphate 10g 77 gr. 
Water » 1000 ccm 16 oz. 
Potassium ferricyanide aS 38 gr. 
Ammonia Gis: q.s 
Add enough ammonia to form a clear solution. This gives 
violet tones. 
Uranium Toninc.—Treatment of a silver image with a 
mixture of a soluble uranium salt and ferricyanide of potas- 
sium results in brown to, red images, the colour being de- 
pendent on the ratio of the two salts and the duration of 
toning. Intensification also takes place; therefore, the prints 
should not be too intense at first. The colour is dependent 
on the deposition of uranium ferrocyanide, which is soluble 
in alkalis. Long washing in ordinary water, therefore, will 
reduce the colour by dissolving the uranous salt. 
The following baths were recommended by Sedlaczek; all 
the quantities given represent the amount of 10 per cent 
solution that should be used, unless otherwise stated: 
Uranium nitrate 50 ccm 350 min. 
Ammonium oxalate 100 ccm 700 min. 
Hydrochloric acid 10 ccm 70 min. 
Potassium ferricyanide 20 ccm 140 min. 
Water 1000 ccm 16 oz. 
This gives brown tones. | 
Uranium nitrate 50 ccm 350 min. 
Potassium oxalate 50 ccm 350 min. 
Hydrochloric acid 10 ccm 70 min. 
Potassium ferricyanide 20 ccm 140 min. 
Water 1000 ccm 16 oz. 
This gives warm brown tones. If a saturated solution of 
oxalic acid be used instead of the potassium oxalate, redder 
tones are obtained. 
Uranium nitrate 50 ccm 350 min. 
