85 
four hours with one-tenth of its volume of strong alcohol in order to 
remove mucilaginous substances, and the filtrate therefrom be mixed 
with four times its volume of absolute alcohol, there is obtained, 
after filtering and drying in vacuo over calcium chloride a dark- 
grayish mass, which on treatment with water dissolves only in part. 
After treatment with water and filtering, a perfectly clear and color- 
less solution is obtained, which shows strong peroxidase reactions, 
but weak oxygenase reactions, and which only acts upon tyrosin 
after standing from thirty-six to forty-eight hours. In other words, 
by the action of alcohol, the activity of the potato tyrosinase has 
been greatly weakened, a fact which is in harmony with Bertrand’s 
earlier observations on the tyrosinase contained in Russula delica. 
According to Bach, it is weakened for the reason that the oxygenase 
moiety of the ferment has been destroyed by the alcohol. He there- 
fore sought to restore it to its original activity by the addition of 
small amounts of hydrogen peroxide. As a matter of fact, the weak 
tyrosinase solutions which only oxidize the tyrosin after thirty-six to 
forty-eight hours, become dark brown in one hour after the addition 
of small amounts of hydrogen peroxide. Bach concludes, therefore, 
that the specific character of tyrosinase lies in the specific nature of 
its peroxidase. 
On the other hand, R. Chodat and Staub ( 11S ) found that hydrogen 
peroxide not only did not accelerate the action of tyrosinase on 
tyrosin, but actually retarded it. As Bach pointed out in his first 
communication on the subject ( 21 ), however, tyrosinase is very sensi- 
tive to the action of hydrogen peroxide, and it is necessary to work 
with very dilute hydrogen peroxide in order to demonstrate the 
accelerating effect. Von Fiirtli and Jerusalem ( 178 ) have also observed 
that small amounts of hydrogen peroxide materially accelerate the 
action of tyrosinase, whereas with larger amounts of the peroxide the 
reaction is retarded. 
More recently Bach ( 23 ) has been able to accelerate the oxidation 
of tyrosin by w T eak tyrosinase from Russula delica by means of hydro- 
gen peroxide. As already pointed out under the preparation of 
tyrosinase (see p. 74), he prepared aqueous extracts of the ferment 
from three lots of the fungus (I, from fresh, unblemished fungi; II, 
from older, more or less damaged fungi, and III, from putrid fungi). 
Portions of these original extracts were diluted ten times with water, 
and 10 c. c. of the diluted extracts were mixed with 10 c. c. of a 
tyrosin solution containing 0.05 per cent of tyrosin and 0.04 per cent 
of sodium carbonate, and 30 c. c. of water added. After standing 
twenty-four hours, 1. c. c. of 10 per cent sulfuric acid was added, and 
each solution was titrated with 0.002 N potassium permanganate to 
complete decolorization. The quantities of permanganate required 
