Outlines of practical physiology : being a manual for the physiological laboratory, including chemical and experimental physiology, with reference to practical medicine / by William Stirling.

  • William Stirling
Date:
1902
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of practical physiology : being a manual for the physiological laboratory, including chemical and experimental physiology, with reference to practical medicine / by William Stirling. Source: Wellcome Collection.

    49/690 (page 19)
    quantities in the blood (o'i to o-2 p.c.) and other fluids and organs. It is the form of sugar found in diabetic urine. After ingestion of large quantities of sugar, a reducing sugar may appear in the urine (“Alimentary glycosuria”). It is very soluble in water and in alcohol. Dissolve a small quantity in hot water (i p.c.). (a) It is not so sweet as cane-sugar. (6) Add iodine solution = no reaction. (c) Heat with H2S04; dark¬ ens slowly. (Distinction from cane-sugar.) (d) Dissolve some in boiling abso¬ lute alcohol. It crystallises in trans¬ parent prisms when the alcohol cools (fig- 2). (e) Heat gently some dry glucose = melts—then yellow and brown = (caramel) with odour of burnt-sugar. A. Some important tests depend on its power of reducing various metallic oxides, especially those of copper. Glucose, like all aldehydes (e.g., formaldehyde, is readily oxi¬ dised. Substances, therefore, that readily give up O are reduced. (a) Trommer’s test.—Add a drop or two of CuS04 solution (io p.c.), and afterwards NaHO (or KHO) in excess, i.e., until the precipitate—hydrated oxide of copper—first formed is re-dissolved, and a clear blue fluid is obtained. The hydrated oxide of copper is .held in solution by dextrose (and by all the glucoses). Heat the upper stratum slowly, turning the tube in the flame. A little below the boiling point, if grape-sugar be present the blue colour disappears, and a yellow (cuprous hydrate) or red (cuprous oxide) precipitate is obtained Avhich contrasts sharply with the deep blue below. The precipitate is first yellow, then yellowish-red, and finally red. The colour is best seen in reflected light. If excess of copper be added, the copper hydrate precipitate masks a small amount of the cuprous precipitate. If no sugar be present, only a black colour may be obtained. [Make a control test with water to show this.] [Ammonia or ammoniacal salts retard the reaction, as the Cuo0 is not precipitated at once. Test this by adding some NH4C1, then perform Trommer’s test.]