65 
to 1.0 per cent solution, in order to prevent the action of the oxidases 
on tyrosin and other chromogens contained in the potato. After 
standing twenty-four hours the mass is strained through a cloth and 
filtered. The clear reddish or yellowish liquid is then saturated with 
ammonium sulfate, and the precipitate, consisting of proteids, coloring 
matter, and ferments, is collected on a filter and washed with satu- 
rated ammonium sulfate solution, and finally dissolved in water. 
This salting out with ammonium sulfate and re-solution in water is 
repeated three or four times. The water solution finally obtained 
was then dialyzed against running water in pergament paper and then 
precipitated with 4 to 5 volumes of 95 per cent alcohol. The pre- 
cipitate thus obtained was collected on a filter, washed with ether and 
dried over sulfuric acid. At the end of a week the yellowish-brown 
powder thus obtained was extracted with distilled water; a water- 
clear solution was thus obtained which, after saturation with chlo- 
roform and standing a month, gave only a slight percipitate (not 
weighable). In order now to obtain the pure ferment, the water 
extract thus obtained was precipitated with 5 or 6 volumes of ethyl 
alcohol, and the precipitate collected and dried over sulfuric acid in 
a desiccator. The yield of pure laccase was so small, however, that 
even after a year only about 1 gram of the material was obtained. 
The yield of laccase from cabbage was found to be even smaller. 
The pure laccase obtained by Slowtzoff was found to give all of the 
reactions for protein and to contain 12.8 per cent nitrogen and 0.53 
per cent of sulfur, and to be very poor in ash. According to this 
author, it belongs to the group of albumins and contains neither man- 
ganese nor phosphorus. 
In order to determine the oxidizing power of his pure preparation, 
Slowtzoff made use of Rohmann’s reagent, viz., a solution of para- 
phenylene diamin and meta-toluylene diamin in sodium carbonate 
solution, the quantity of coloring matter produced by the action of 
the ferment or other oxidizing agent, such as a ferric salt, being esti- 
mated colorimetrically. On the basis of these observations, he 
arrived at the following conclusions respecting the nature of laccase 
and its mode of action : 
(1) Laccase belongs to the group of ferments for the reason — 
(a) That it loses its activity at high temperatures. In this connection he found 
the thermal death point of the ferment to vary with the degree of purity of 
the preparation; thus his purest preparations lost their activity at as low a 
f temperature as 50° C., whereas preparations richer in ash only lost their 
activity at temperatures of from 65° to 70° C. 
(6) The amount of the substance oxidized is proportional to the square root of the 
quantity of laccase present. 
(c) The quantity of product resulting from the action of the ferment is propor- 
tional to the quantity of the ferment, but not to the amount of substances 
being oxidized. 
11670— Bull. 59—10 — -5 
