144 PHOTOGRAPHIC FACTS AND FORMULAS 
This forms an excellent non-staining reducer for developed 
prints if diluted with 10 times its volume of water. 
MeERcuRY AND CYANIDE (Eder).—An extremely poisonous 
but non-staining reducer: 
Mercuric chloride 2.5¢ 19 gr. 
Water 1000 ccm 16 oz. 
Dissolve, and add: 
Potassium iodide 2.08 19 gr. 
Red mercuric iodide is precipitated, which is dissolved by 
the addition of : 
Potassium iodide | 5g 38 gr. 
This acts rapidly. It is suitable for developed prints if 
diluted with 10 parts of water. A variant of this is to replace 
the iodide with a like quantity of sodium carbonate crystals. 
Cupric CHLORIDE (Spiller) — 
A. Alum 100 g 134 oz. 
Cupric chloride 100 g 134 oz. 
Salt 200 g 34 oz. 
Hot water 1000 ccm 16 oz. 
Dissolve, and filter when cold. 
B. Saturated solution of salt. 
For use mix in equal volumes. When the negative is nearly 
sufficiently reduced, wash. This cannot be recommended, as 
the reducing action continues too much during the washing. 
A variation of the above (Fourtier) has been suggested: 
Cupric sulphate 5g 38 gr. 
Water 100 ccm 2 Gn. 
Dissolve, and add solution of potassium carbonate until no 
further precipitate is formed. Collect the precipitate on a 
filter, wash with several changes of water, and then dissolve 
in: 
Hydrochloric acid q. S. | 
Water 25 ccm YZ 02. 
