Abstract
To 1 c.c. of blood serum in a 10 c.c. test-tube, add 4 c.c. of a 1 per cent. solution of ammonium oxalate. Let stand for 1/2 to 1 hour, and centrifuge for 5 minutes. Pour off the supernatant fluid. Wash the precipitate three times with distilled water, recovering the precipitate by means of centrifugalization. Add to sediment 1 c.c. distilled water and transfer to a vitreosil crucible. The test-tube is washed with distilled water and the washings also collected in the crucible. The water is slowly evaporated, and the precipitate burnt in a strong flame until CaO is formed. Dissolve the ash in 1/2 c.c. N/50 HCl, add 1 c.c. distilled water and titrate excess of HCl with N/100 NaOH, using phenolphthalein as an indicator. The amount of CaO can now be calculated.
Eight analyses may be made by this method in one hour. Remarkably uniform results are obtained upon repeated examinations of the same blood. For clinical purposes, this method is of great assistance.
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