QUANTITATIVE ESTIMATION OF LACTIC ACID 453 



the results from such methods seem extremely unreliable. 

 Boas had originally recommended that in qualitative de- 

 termination of lactic acid (as in gastric juice) the fluid under 

 examination be distilled with manganese and sulphuric acid 

 and the acetaldehyde, formed according to the equation : 



CH 8 



CH 8 

 CH.OH + O - I + C0 2 + H a O, 



COH 

 COOH 



be determined by transforming it into iodoform with an 

 alkaline solution of iodine. E. Jerusalem having shown in 

 the author's laboratory that oxidation of lactic acid in hot 

 sulphuric acid solution by the addition of drop after drop 

 of permanganate solution may be employed for the purpose 

 of quantitative determination, 1 the author, in collaboration 

 with D. Charnass, 2 worked out a reliable method based upon 

 this principle for its quantitative estimation. They were 

 able to show that oxidation cleavage of aldehyde from lactic 

 acid occurs when certain experimental conditions are main- 

 tained, even if not absolutely quantitatively, at least with 

 such a degree of uniformity that a quantitative method can 

 very well be based upon this process as a foundation. Titri- 

 metric estimation of aldehyde by the iodoform method gives 

 reliable results only when very exact experimental condi- 

 tions are maintained. It is very inferior in practice to the 

 iodometric method of Kipper based on the addition of 

 bisulphite : 



CH 8 CH 3 



I + NaHSO, = I /H 

 COH 6A)Na 



\BS0 3 , 



as the latter yields almost theoretically correct results. 3 The 



*E. Jerusalem (under direction of 0. v. Ftirth), Biochem. Zeitschr., 12, 

 361, 379, 1908 j O. v. Ftirth, Emendation to article of E. Jerusalem, ibid., 24, 

 266, 1910. 



2 O. v. Ftirth and D. Charnass, Biochem. Zeitschr., 26, 199, 1910. 



8 Cf. also W. Sobolowa and J. Zaleski (St. Petersburg), Zeitschr. f. physiol. 

 Chem., 69, 441, 1910. 



