132 PHOTOGRAPHIC FACTS AND FORMULAS 
are allowed to remain too long in this solution, they are 
reduced ; 
F. Mercuric-iodo-cyanide (Eder) : 
Potassium cyanide 5g 38 gr. 
Potassium iodide 252 19 gr. 
Mercuric chloride 25'2 19 gr. 
Water 1000 ccm 16 oz. 
The bleached image first turns yellowish, then dark brown, 
and, if the plate be removed at this stage, it will generally be 
too dense for practical purposes; if the action is allowed to 
continue longer, the image turns a lighter brown and becomes 
more transparent ; 
- G. Schlippe’s salt or sodium sulphantimoniate : 
Schlippe’s salt 25¢ 192 gr. 
Ammonia 10 ccm 77 min. 
Water 1000 ccm 16 oz. 
Make just before use and filter. Gives a brownish-red image 
which is too dense for ordinary work. This is useful for 
restoring negatives intensified with mercury, which have 
faded with course of time; 
H. Sodium sulphide 10¢g 77 gr. 
Water 1000 ccm 16 oz. 
Usually gives too much intensification for ordinary work; 
I. Formalin with caustic soda has been recommended for 
blackening the bleached images, but presents no advantage; 
J. Stannous tartrate (Helain) : 
Stannous chloride 20 g 154 gr. 
Tartaric acid 20g 154 er. 
Water 1000 ccm 16 oz. 
This has also no special features to recommend it. 
Practically, it may be said that, assuming the original den- 
sity of the negative to be 1, the intensification given by A, B, 
C, E will be 2, by D about 2.5. Repeated bleaching with” 
