A laboratory manual of physiological chemistry / by Ralph W. Webster and Waldemar Koch.

  • Webster, Ralph W. (Ralph Waldo), 1873-1930
Date:
1903
Catalogue details

Licence: In copyright

Credit: A laboratory manual of physiological chemistry / by Ralph W. Webster and Waldemar Koch. Source: Wellcome Collection.

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    osmium, a reaction characteristic of all fats containing oleic acid. State in your notebook your conclusions as to the natme of leci- thin. Consult your text-book for its formula. EXPERIMENT II. Cholesterin.—The acetone solution from which the lecithin has been precipitated is evaporated on the steam-bath. 1 he 1 esi- due is dissolved in 50 c.c. of alcoholic sodium hydrate (10 per cent.) and heated on the steam-bath in a flask until all the alcohol has evaporated. dhe residue is dissolved in 50 c.c. of water, transferred to an evaporating dish, 10 g. of sodium chloride added, and again evaporated to complete dryness. This residue is then ground fine in a mortar, dried at 105 C., and exti acted with 30 c.c. of cold ether. The ether solution is filtered and should leave on evaporation crystals of cholesterin. Reactions of cholesterin. 1. Evaporate with nitric acid. A yellow mass is obtained which turns brick-red on addition of ammonia. 2. Mixed in the dry state with strong sulphuric acid, it pro- duces a blue-red or violet color on addition of chloroform, the color changing to green on exposure to air. 3. Evaporated with a mixture of two volumes of sulphuric acid and one volume of ferric chloride solution, it turns violet. 4. Dissolve in chloroform and observe crystals on evaporation, under microscope. Make drawing of crystals in your notebook, and consult text-book for chemical nature of cholesterin. See Plate II. Some cholesterin may also be obtained in the same manner from the acetone solution derived from yeast. EXPERIMENT III. Nucleic acid.—Take the yeast residue from the alcohol-ether extraction and treat it with 50 c.c. of 10 per cent, sodium carbon- ate solution for one hour at 30° to 40°. Filter and allow to cool. Save the residue for inorganic salts. After the filtrate has cooled, carefully add acetic acid until solution is slightly acid. A turbidity will be noticed, due to precipitation of the nucleo-albumins present
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