454 LACTIC ACID 



amount of aldehyde obtained from lactic acid in the v. Fiirth 

 and Charnass tests averaged eighty-nine per cent, of the 

 theoretical value; and the constant error is taken into ac- 

 count by introducing a correction factor. In Embden's 

 laboratory 4 several improvements have recently been made 

 in the method, which make it satisfy even far reaching re- 

 quirements. The aldehyde recovery of the original method 

 particularly can be increased by using a very dilute solution 

 of permanganate (n/100 instead of n/10 solution) for 

 oxidizing purposes. 



Observations in Embden's laboratory show the need 

 which existed for replacing the weighing of the zinc lactate 

 by another and better method. This is done by extracting 

 the lactic acid for about twenty-four hours in the Lindt 

 rotary apparatus (which forces a whirl of very fine ether 

 bubbles through the fluid) and removing the lactic acid from 

 the etheral extract for weighing as zinc lactate. Control ex- 

 periments by the author's method show that in determina- 

 tions of lactic acid from tissue extracts made by weighing 

 the lactate of zinc, the zinc salts contain so many impurities 

 at times that no fixed conclusions can be drawn as to the 

 amounts of lactic acid present by mere weighing. 5 



A source of error until recently entirely overlooked in 

 the determination of lactic acid in tissues may arise from 

 the fixation of the free lactic acid by the tissue proteins. 

 J. Mondschein, 6 for example, has determined in the author's 

 laboratory that the previously existing statements as to the 

 amount of lactic acid in muscle are too low, as about one- 

 third of the lactic acid present (which, if the tissue is well 

 boiled, remains fixed in the coagulum because of combina- 

 tions with proteins) escapes estimation. However, the 



4 G. Embden, Handb. d. biochem. Arbeitsmeth., 5, 1255-1259, 1912. 

 "S. Oppenheimer (Embden's Lab.), Biochem. Zeitschr., 45, 30, 1912. 

 6 J. Mondschein (under direction of O. v. Fiirth), Biochemic. Zeitschr., 42, 

 105, 1912. 



