INTENSIFICATION 137 
This should be added cautiously to the tin solution, with con- 
stant stirring, so that the precipitate first formed is not quite 
cleared up. The solution should then be filtered, and the bulk 
made up to 1000 ccm (16 oz.) with water. A variation of 
this method is to treat the bleached image with a 5 per cent 
solution of caustic soda, wash, and then with 10 per cent of — 
stannous chloride. The cupric chloride may be replaced by: 
Cupric sulphate _ 44¢ 34 gr. 
Salt 20.8 g 160 gr. 
Hot water 1000 ccm 16 oz. 
Mix and allow to cool before use. 
CopPpER FERROCYANIDE INTENSIFIER.—This is very rarely 
used, and is apt to give too great intensification. The degree 
of increase depends on the duration of the action of the bath 
and the consequent warmth of colour. Two stock solutions 
are required : 
1. Cupric sulphate Al Xs 54 gr. 
Potassium citrate, neutral 28 g 215 ger. 
Water 1000 ccm 16 oz. 
II. Potassium ferricyanide 6g 46 gr. 
Potassium citrate, neutral 28g Z215er: 
Water 1000 ccm 16 oz. 
Mix in equal quantities just before use. No. II solution must 
be kept in the dark. A variation of this is to mix the two 
solutions and to add enough strong ammonia to form a clear 
solution. 
THe URANIUM INTENSIFIER.—Except for extremely thin 
and flat negatives, this is not to be recommended. The 
degree of intensification depends upon the ratio of the 
uranium to the ferricyanide: 
I. Uranium nitrate 100 g 768 gr. 
Glacial acetic acid 40 ccm 300 min. 
Water 1000 ccm 16 oz. 
