MEASUREMENT OF OXYGEN CONSUMPTION 541 



Leukomalachite-green Method. The author believes a 

 real advance has been made in the f discovery in leukomal- 

 achite-green of a reagent which possesses the advantages 

 but not the disadvantages of phenolphthalin. The leuko- 

 base of malachite-green, in its chemical construction a tri- 



phenylmethane derivative, CH^-C^ 6 N(CH 3 ) 2 , is recommended 



\CeH4 N(CH 3 )2 



by E. and 0. Adler 10 as an extremely reliable reagent, the 

 colorless solution of the substance being changed into mal- 

 achite-green at once in the presence of hydrogen peroxide 

 by very small amounts of blood. It was found by the 

 author and his associate that a solution of the leukobase in 

 acetic acid with hydrogen peroxide added serves also as an 

 excellent reagent for the detection of peroxidases. The 

 solution remains unchanged for a relatively long time; but 

 on the addition of a small amount of a solution of a per- 

 oxidase at once an emerald green color appears, deepening 

 more or less rapidly. As a properly diluted solution of 

 malachite-green shows a sharply defined absorption band in 

 the middle of the spectrum, it is quite possible to determine 

 quantitatively by spectrophotometry the amount of mal- 

 achite-green which has been produced by the enzymic influ- 

 ence from the leukobase with considerable accuracy. As 

 the observation requires but a few moments, and can be 

 repeated as often as may be desired and at whatever inter- 

 vals may seem best in the same test, one is in position, even 

 if only a few cubic centimeters of material be available, to 

 follow the process of oxidation step by step and record it 

 graphically by a curve (with the time as abscissa and the 

 amount of newly formed malachite-green as ordinate). 



Measurement of Oxygen Consumption. C. Foa pro- 

 ceeds upon a difficult principle, registering by means of a 

 Mosso phethysmograph the amount of oxygen consumed in 

 the oxidation of aromatic substances (pyrogallol, hydro- 

 chinon, etc.) by peroxidases (the method being based on 



10 R. and O. Adler, Zeitschr. f . physiol. Chem., 41, 58, 1904. 



