INTENSIFICATION 133 
_ mercury and development with ferrous oxalate will give any 
desired degree of increase. 
Mercuric Iodide (Edwards, Lumiére, etc.)—As originally 
recommended by Edwards, this was a solution of mercuric 
iodide in excess of iodide and hypo, as follows: 
Mercuric chloride I2¢ 97 sr. 
Water 650 ccm 10 oz. 
Dissolve and add: 
Potassium iodide 33 g 253 er. 
Water 100 ccm 2 oz. 
And, finally: 
Hypo 27 g 207 gr. 
Water 250 ccm 4 oz. 
MM. Lumiére suggested: 
Mercuric iodide 10g 77 gr. 
Sodium sulphite, dry 100 g 770 gr. 
Water 1000 ccm 16 oz. 
This is an improvement on the first formula. The negatives 
assume a dark brown colour, but the image is not stable and 
soon turns yellow. It is advisable, therefore, to treat the 
darkened image with a developer, which renders it per- 
manent. Welborne Piper proposed the following: 
A. Mercuric chloride 50 g 384 gr. 
Hot water LOO cena: 16 oz. 
B. Potassium iodide 50 g 384 gr. 
Cold water 250 ccm 4 oz. 
Add B to A gradually, shaking after each addition until the 
solution becomes clear, and, if necessary, heating. After all 
B has been added and the solution is clear, allow to cool and 
filter out any red precipitate formed. The negatives should 
be bleached in this solution, washed and treated with sodium 
sulphite or ammonia, or redeveloped, and well washed. 
Mercuric Sulphocyanide (Agfa)—This was patented in 
