Abstract
The red color obtained by heating a dextrose solution with picric acid and sodium carbonate is employed as the basis of the present method for the determination of blood sugar, the reaction being so delicate that it is possible to determine the dextrose in as little as 0.5 c.c. of blood. Following is the method in detail as ordinarily used by us.
Two c.c. of blood are drawn from a vein through a hypodermic needle into an Ostwald pipette, a little potassium oxalate in the tip of the pipette preventing clotting. The blood is discharged immediately into a 25 c.c. volumetric flask containing 10 c.c. of N/100 acetic acid previously heated in a boiling water bath. The pipette is rinsed once with distilled water. The flask is replaced in the boiling water bath and shaken occasionally for five minutes. After cooling, 1 c.c. of 5 per cent. dialyzed iron (Merck) is added to precipitate any protein still in solution. Distilled water is added to the mark, the contents of the flask are filtered, and an aliquot of the clear filtrate (10 c.c. or 15 c.c.) is measured into a large Jena test tube (200 × 22 mm.) and evaporated to 1 c.c. or below (but not to dryness) over a direct flame, two glass beads being used to prevent bumping. Two c.c. of saturated picric acid solution and 3 c.c. of 20 per cent. sodium carbonate are added and the tube is placed in a boiling water bath for ten minutes. The contents of the tube are then cooled and washed quantitatively into a 10 c.c. volumetric flask. After making up to the mark, the red solution is filtered into the colorimeter chamber and read at once against a standard freshly prepared by the same procedure from 1 c.c. of a solution containing 1 mg. of dextrose per c.c. The standard is usually set at 15 mm.
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