124 PHOTOGRAPHIC FACTS AND FORMULAS 
Acid bath— 
Hypo 150g 2Y4 oz. 
Potassium metabisulphite 25g 4 oz. 
Water 1000 ccm 16 oz. 
This is about the correct strength for papers; for negative 
work the hypo should be increased to 400 g (614 oz.). An 
equally efficient bath is made as follows: 
Hypo 400 g 64 oz. 
Citric acid 30 g 230 gr. 
Sodium sulphite, dry 35,2 270 gr. 
Hot water to 1000 ccm 16 oz. 
Dissolve the hypo in half the water and the acid and sulphite 
in one-fourth, mix the solutions and make up to bulk. 
Acid-alum bath.—The following is typical of the formulas 
recommended by plate and film makers: 
Hypo 250 g 16 oz. 
Water 1000 ccm 64 oz. 
Dissolve and add: } 
Sodium sulphite, dry 31g YZ oz. 
Acetic acid, No. 8 186 g 3 0Z. 
Alum Sle 4 oz. 
Water 312 ccm 5 oz. 
Dissolve the chemicals in this order. Some paper makers 
recommend the same bath, but with double the quantity of 
sulphite and alum, for developed prints. 
Acid-chrome alum bath.— 
Sodium sulphite, dry 45 ¢ 34 ox 
Water 100 ccm LY oz. 
Stir well and add: 
Glacial acetic acid 20 ccm 154 min. 
Then add to the following, after the hypo is dissolved: 
Hypo 400 g 6¥4 oz. 
Hot water 600 ccm 9 oz. 
