Directions for laboratory work in physiological chemistry : for the use of students in the University and Bellevue Hospital Medical College / Holmes C. Jackson.

  • Jackson, Holmes C. (Holmes Condict), 1875-
Date:
1902
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Licence: In copyright

Credit: Directions for laboratory work in physiological chemistry : for the use of students in the University and Bellevue Hospital Medical College / Holmes C. Jackson. Source: Wellcome Collection.

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    tate, which is at first formed, dissolves. Then add a few drops of the dextrose solution and warm on the water-bath. Note the formation of a metallic mirror on the side of the test-tube. Explain chemical changes. (g) Phenylhydrazin.—In a test-tube make a mixture of 5 drops phenylhydrazin, 10 drops glacial acetic acid, and 1 c.c. of a saturated solution of NaCl; then add 5 c.c. of the dex- trose solution and boil for a few minutes. Yellow phenyl- glucosazone crystals will appear on cooling. These must be examined under the microscope. This is the most distinc- tively characteristic and conclusive of all tests for dextrose. The crystalline form is the important point. Other sub- stances form osazones, but these latter differ in crystalline form, solubilities, and melting-points. Write the chemical equations for the formation of osazones. (h) Fermentation.—In a test-tube shake 20 c.c. of the dex- trose solution with a small piece of compressed yeast. Place the mixture in a saccharometer and allow it to stand in a thermostat at 40° C. A gas (?) collects at the top of the tube and the amount is in a direct ratio to the amount of dextrose in the solution. What is the character of the chemical changes which have taken place? Disaccharides, C12H22Ou. Maltose. Lactose. Saccharose. Saccharose = cane sugar = sucrose. Tests: (a) Fehling’s; Moore's; Nylander's; Fermentation; Barfoed’s; using in each case 5 c.c. of the saccharose solu- tion. Compare the results with those obtained with dex- trose. (b) To 10 c.c. of the saccharose solution add 1 c.c. concen- trated HC1 and boil several minutes. Allow to cool and