. Cyclopedia of farm animals. Domestic animals; Animal products. 180 MILK AS A MARKET PRODUCT lows: Add lime-water to 25 cc. of milk until the mixture is alkaline ; evaporate to dryness and burn to an ash in a small porcelain or platinum dish. Add a few drops of dilute hydrochloric acid to the ash, care being taken not to use too much acid, then add a few drops of water, and place a strip of tumeric paper in this water solution. Dry the paper, and if either borax or boric acid is present, a cherry-red color will appear. This test is con-. Fig. 169. Mann's acid test outfit. firmed by moistening
. Cyclopedia of farm animals. Domestic animals; Animal products. 180 MILK AS A MARKET PRODUCT lows: Add lime-water to 25 cc. of milk until the mixture is alkaline ; evaporate to dryness and burn to an ash in a small porcelain or platinum dish. Add a few drops of dilute hydrochloric acid to the ash, care being taken not to use too much acid, then add a few drops of water, and place a strip of tumeric paper in this water solution. Dry the paper, and if either borax or boric acid is present, a cherry-red color will appear. This test is con-. Fig. 169. Mann's acid test outfit. firmed by moistening the reddened paper with a drop of an alkali solution, when the paper will turn to a dark olive color, if borax or boric acid is present. Test for coal-tar dyes. Van Slyke also describes a test for this form of milk adulteration. Add 10 cc. of milk to 10 cc. of strong hydrochloric acid, and mix. A pink color appears if coal-tar dyes have been used. Test for boiled milk. It is sometimes desirable to determine whether milk has been subjected to 176° Fahr. or higher heat. A successful test has been devised by Storch. To 5 cc. of the suspected milk add a few drops of potassium iodid and a similar quantity of starch solution, also a few drops of hydrogen peroxid. If the milk has not been cooked, an enzyme which is present will decompose the hydrogen peroxid, set- ting free oxygen. This combines with the potassium salt and thus iodine is in turn set free and with the starch it forms a purple color. If the milk has been heated so that the enzyme is killed, no color will result. Another test for cooked milk is given by Arnold, as follows: Tincture of guaiac is added, drop by drop, to a little milk in a test-tube. If the milk has not been heated to 176° Fahr., a blue zone is formed between the two fluids. If it has been heated, there is no reaction. The guaiac-wood tincture is said to be more reliable than other tinc- tures, and it should not be used when fresh, but when at least a fe
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