The lactic acid content of blood and spinal fluid

Abstract

As a preliminary to the study of variations of the concentration of lactic acid in blood and spinal fluid in pathological conditions, it was found essential to establish the normal limits for human blood and spinal fluid. Clausen's method has been adopted as the most satisfactory procedure. This method comprises the following steps: The precipitation of the blood proteins by tungstic acid by the Folin-Wu procedure, and the removal of glucose from this filtrate by means of copper sulphate and calcium hydroxide; the extraction of the lactic acid from this glucose-free filtrate with ether; the oxidation of the lactic acid to acetaldehyde with potassium permanganate; the distillation of the acetaldehyde into sodium bisulfite solution, and the titration of the excess and combined bisulfite, with iodine. With this method, Clausen states the provisional figures for normal human blood are from 15 to 32 mg. per 100 cc. This indicates a variation of more than 100 percent. The object of the present study was to investigate the lactic acid content of normal blood under standard conditions, eliminating all the known sources of error. The distillate is received into approximately 0.02 N NaHSO₃. This solution keeps but a short time. It was prepared daily from 0.1N stock solution. Kahlbaum's sodium bisulfite has been used. The solution must be stoppered and preserved on ice. This 0.1N solution was daily standardized against iodine. For the determination of the excess bisulfite 0.02 N iodine was employed and for the bound bisulfite 0.01 N. The iodine must be daily standardized against Na₂S₂O₃, and this in turn is checked against K₂, Cr₂,0₇. It is necessary to use very pure NaHCO₃. Kahlbaum's and Merck's reagent products were found satisfactory.