136 PHOTOGRAPHIC FACTS AND FORMULAS 
If still greater density be required, the negative should be well 
washed after bleaching and redeveloped with any ordinary 
developer, the silver treatment being omitted. Or, after 
washing, the negative may be blackened with a 0.5 per cent 
solution of sodium sulphide. 
As an improvement on the silver nitrate, which may cause 
stains, Namias recommends silver oxalate. To prepare this, 
take: 
Silver nitrate 10g 77 gr. 
Water 100 ccm 2 02: 
Dissolve, and add: 
Potassium oxalate, neutral 6g 46 gr. 
Water 50 ccm 1 og: 
Allow the silver oxalate to settle down, decant the water, and 
add the precipitate to 1000 ccm (16 oz.) water. Shake the 
solution every time before applying to the bleached negative. 
The process is applicable to papers as well as plates, and it is 
advisable to subsequently immerse in a 10 per cent solution 
of hypo for a few minutes and wash well. 
Tue Copper-T1n INTENSIFIER.—In this the final image 
consists of a mixture of tin and silver compounds, and the 
intensification is due to a great extent to the non-actinic colour 
of the deposit, which is a warm brown. Bleach the negative 
in: 
Cupric chloride 30 g 230 gr. 
Hydrochloric acid 3 ccm 23 min. 
Water 1000 ccm 16 oz. 
Wash thoroughly and immerse in the following: 
Stannous chloride 40¢g 307 gr. 
Water 400 ccm 4 oz. 
To which is added: 
Caustic soda 30 g 230 gr. 
Water 100 ccm 1 oz. 
