A sample of leather 2 1/2 inches square and weighing from 2 to 6 grams is placed on a glass plate, flesh side up, and evenly dampened with a So solution of sulfuric acid in the proportion of 1 ml of acid solution per gram of air dry leather.
After remaining at room temperature overnight, hydrogen peroxide (10 vol. strength) is applied uniformly to the specimen, in the proportion of 0.6 ml per gram of leather. The specimen is then given additional treatments with hydrogen peroxide every 24 hours. This procedure is said to cause unsatisfactory leather (leather lacking in permanence) to become blackened and gelatinized whereas satisfactory (permanent) leather will be unaffected, except for possible discoloration of the edges. Changes in the color of dyestuffs are said to he immaterial. (237 , 351 )