. Essentials of medical and clinical chemistry. With laboratory exercises . ayer, that gathers atthe top of milk when allowed to stand. This not only deprives 401 Let the student boil some milk in a test-tube, then close it with a plug ofdry absorbent cotton and set it aside to note that it remains sweet and unalteredfor days and weeks. The teacher should also show some standard sterilizer, asArnolds. PART III.—CLINICAL CHEMISTRY. 221 the milk of a valuable constituent, but, unless the new and rapidcentrifugal process is used, delays its delivery for at least half aday, thus increasing the dan
. Essentials of medical and clinical chemistry. With laboratory exercises . ayer, that gathers atthe top of milk when allowed to stand. This not only deprives 401 Let the student boil some milk in a test-tube, then close it with a plug ofdry absorbent cotton and set it aside to note that it remains sweet and unalteredfor days and weeks. The teacher should also show some standard sterilizer, asArnolds. PART III.—CLINICAL CHEMISTRY. 221 the milk of a valuable constituent, but, unless the new and rapidcentrifugal process is used, delays its delivery for at least half aday, thus increasing the danger of contamination and decompo-sition \ (c) dilution?®1 which is a very common practice, but lessdangerous to health, unless the water is contaminated withtyphoid or other infectious germs. Milk Testing.—The specific gravity of good milk should notbe below 1029 unless the milk is unusually rich in fats, which beinglighter than the rest of the milk, lowers the specific gravity \ andif it rises above 1035 the milk has probably been skimmed. Fig. 69. Fig. 70. d j>. Iro- Creamo-:er. meter. (Starr.) Fesers Lactoscope.(Queen.) Skim milk, however, may be so diluted as to bring its specificgravity within the ordinary limits, but an experienced eye canreadily see that instead of being white, the milk assumes a bluishtinge, or in other words loses the natural opacity imparted bythe suspended oil globules. So the measurements of the specific 402 Let the student dilute a specimen of milk in a test-tube or beaker, andnote the bluish tint produced. 2 22 ESSENTIALS OF CHEMISTRY. gravity are not conclusive unless the opacity be also observed : Thisis easily done by the lactoscope (Fig. 7o),40H which consists of acylinder of clear glass (A), containing at the lower part a smallercylinder of white glass (resembling that shown at x, fig. 70), uponwhich are a few black lines. In testing, 4 Cc. of the milk are intro-duced from the graduated pipette {B)^ and the black lines are en-tirely c
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