4378. To Detect Mineral Substances in Flour

4378.     To Detect Mineral Substances in Flour. The presence of a mineral adulteration of flour or meal may bo readily detected. A small quantity of the suspected flour is shaken up in a glass tube with chloroform. All mineral adulterations will collect at the bottom, while the flour will float on the liquid.

4379. How to Know Good Flour

4379.       How to Know Good Flour. "When flour is genuine or of the best kind, it holds together in a mass when squeezed by the hand, and shows the impressions of the fingers, and even of the marks of the skin, much longer than when it is bad or adulterated; and the dough made with it is very gluey, ductile, and elastic, easy to be kneaded; and may be flattened and drawn in every direction without breaking.

4380. To Detect Adulterations in Sugar

4380.    To Detect Adulterations in Sugar. Sugar is largely adulterated. Pure cane and beet sugars may be known by their solutions bending the luminous rays in cir-cumpolarization to the right, whereas grape and fecula sugars bend it to the left. Pure cane sugar boiled in a solution of caustic po-tassa remains colorless, but if starch sugar is present the liquid turns brown. A filtered solution of 33 grains cane or beet sugar in 1 ounce water, mixed with 3 grains pure caustic potassa, and then agitated with 11/2 grains sulphate of copper in a close vessel, remains clear, even after the lapse of several days; but if starch sugar is present, a red precipitate is formed after some time, and if present in considerable quantity the copper will be wholly converted into oxide within 24 hours; the solution first turns blue or green, and then entirely loses its color. Of late years moist sugar has been largely adulterated with the sweet waste liquor (solution of glycerine,) of the stearine manufactories; but this fraud may be detected by its inferior sweetness, and by its moist and dirty appearance.

4381. Test for Starch

4381.    Test for Starch. The old and familiar test for starch is the blue color which free iodine produces when brought in contact with it; but this is not the only reagent by means of which we can detect the presence of starch in combination with similar bodies. Bromine is nearly as good as iodine, and tannin is said, in some instances, to be better. A solution of 50 grains tannin in 1/2 pint distilled water will answer for making the test. A drop of this tannin solution will cause a precipitate in extremely dilute solutions of starch; the precipitate dissolves when warmed and reappears when the solution cools; and where the starch paste is old, the reaction is said to be more sensitive than that of iodine.

4382. To Test Arrow-Boot

4382.    To Test Arrow-Boot. Genuine arrow-root is odorless and tasteless, and produces a sort of crackling noise when pressed or rubbed, and emits no peculiar odor when mixed with muriatic acid. Stirred up in a mortar with double its weight of a mixture of equal parts of aqua-fortis and water, it does not become gelatinous and adhesive in less than 15 minutes.