THE DETERMINATION OF LACTIC ACID

Abstract

In previous papers (1, 2) the conditions for the oxidation of lactic acid to acetaldehyde, quantitatively, and the accurate determination of the latter, were described.It was found that the oxidation to acetaldehyde appears to depend upon factors such as the concentration of oxidizing agent added, the acidity of the solution, the concentration of MnS04, and probably also the amount of lactic acid oxidized.The maximum yields were obtained with very dilute solutions of oxidizing agent and a high concentration of MnSO1.From these studies we were of the opinion that the conditions necessary for the maximum yield of acetaldehyde were also those which tended to reduce the oxidation potential of the oxidizing agent.We described procedures for the determination of lactic acid, based upon these studies, which in our hands we had found to give the best results at that time.Peculiar difficulties have since then arisen.The proximity to pathological laboratories, in which formaldehyde and acetone were being used, and an unusually cold water supply during the winter months, which made the reflux condensers too efficient, forced us to abandon the aeration procedure first recommended.The oxidation and distillation, which we now use and which is described in this paper, is similar in many respects to the older published methods of Boas (3) and von Ftirth and Charnass (4).In order to obtain maximum and reproducible results the oxidation must be carried out under certain prescribed conditions.Since the bisulfite-binding substances produced by oxidation of substances other than lactic acid are not completely removed by a condenser, as in the aeration procedure of Friedemann, Cotonio,