92 PHOTOGRAPHIC FACTS AND FORMULAS 
Metol lg 7./ gr. 
Potassium bromide 2g 15.4 gr. 
Water 1000 ccm 16 oz. 
The metol exerts a protective action for the amidol. 
Desalme has suggested as a preservative stannous tartrate, 
which is made as follows: 
Stannous chloride 50 g 384 gr. 
Tartaric acid 70g 538 gr. 
Boiling water _ 350 ccm 5Y4 oz. 
To this add the following solution: 
Sodium carbonate, dry 55/5 422 gr. 
Warm water 300 ccm 5.02: 
Filter the mixture and make up to 1000 ccm (16 0z.). Make 
the amidol developer stock as follows: 
Amidol IS g 115 gr. 
Sodium sulphite, dry Ste 422 gr. 
Stannous tartrate, as above 100ccm 768 min. 
Water 1000 ccm 16 oz. 
For use dilute with 2 parts of water and add 3 per cent of 
sodium bisulphite lye. This stannous tartrate solution may 
also be successfully used with other developing agents. An- 
other method of making the stannous tartrate solution is as 
follows: 
Stannous chloride 10g 77 gr. 
Tartaric acid I5¢g 115 gr. 
Water 50 ccm 1 oz. 
And add: 
Sodium carbonate 25g 192 gr. 
Water 250 ccm 5 oz. 
Filter and make up the bulk to 1000 ccm (16 oz.). 
Glycollic and lactic acids have also been recommended as 
preservatives and act well: 
