Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . e by mixing copper sulphateand potassium hydroxide. Add a little glycerolto this suspended precipitate and note whatoccurs. 13. Iodine Absorption Test.—Dissolve asmall amount of an unsaturated organic acid,, oleic acid, in chloroform. Add 2-3 dropsof Hiibls iodine solution^ and shake. The solu-tion will be decolorized if unsatiirated acids arepresent. This is due to the absorption of theiodine. The test should be controlled by shak-ing chlorofor
Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . e by mixing copper sulphateand potassium hydroxide. Add a little glycerolto this suspended precipitate and note whatoccurs. 13. Iodine Absorption Test.—Dissolve asmall amount of an unsaturated organic acid,, oleic acid, in chloroform. Add 2-3 dropsof Hiibls iodine solution^ and shake. The solu-tion will be decolorized if unsatiirated acids arepresent. This is due to the absorption of theiodine. The test should be controlled by shak-ing chloroform and iodine solution to which noacid has been added. 14. Melting-point of Fat.—First Method.— Insert one of the melting-point tubes, furnished by the instructor, into theliquid fat and draw up the fat until the bulb of the tube is about one-half fullof the material. Then fuse one end of the tube in the flame of a Bunsen burner Mandel and Neuberg: Block. Zcil., 71, 214, 1915.^ Made according to Raschig: Bcr., 40, 4586, 1907. Prepared by dissolving 26 grams of iodine and 30 grams of mercuric chloride in oneliter of 95 per cent OS Fig. 54.—Melting-pointApparatus. 184 PHYSIOLOGICAL CHEMISTRY and fasten the tube to a thermometer by means of a rubber band in such a maimerthat the bottom of the fat colomn is on a level with the bulb of the thermometer(Fig. 54, p. 183). Fill a beaker of medium size about two-thirds full of water andplace it within a second larger beaker which also contains water, the two vesselsbeing separated by pieces of cork. Immerse the bulb of the thermometer andthe attached tube in such a way that the bulb is about midway between theupper and the lower surfaces of the water of the inner beaker. The upperend of the tube being open it must extend above the surface of the surround-ing water. Apply gentle heat, stir the water, and note the temperature atwhich the fat first begins to melt. This point is indicated by the initial trans-parency. For or
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