Domestic Tests for Food Adulterations #249960

Bread is adulterated with sulphate of copper, and alum, and other substances which cost less than wheat flour. The most easily applied process of detecting sulphate of copper and alum in bread, is that described by Mr. Horsley. A tincture of Logwood is made by digesting a quarter of an ounce of freshly cut chips in five ounces of methylated spirit, for eight hours, and filtered. A teaspoon ful of this tincture is put with a like quantity of a saturated solution of carbonate of ammonia in a wine glass of water, and the mixed solutions, which are of a pink color, are then poured into a white ware plate or dish. A slice of the suspected bread is allowed to soak in it for five minutes, after which it is placed upon a clean plate to drain, and, if alum be present, it will in the course of an hour or two acquire a blue color; if the tint be greenish, it is a sign of sulphate of copper whereas pure bread gradually loses its pink color; but never turns green or blue.' Sulphate of copper is used by bakers to make very white bread. Alum is used by bakers to make the loaves of bread weigh more by absorbing a larger per cent. Of water in a way which is not detected by its appearance.