64 
unknown to us. Thus it is not an unusual thing to find that extracts 
of the peel of the potato lose their power to oxidize guaiaeum after 
standing a few hours, {see Kastle and Shedd 247 ), whereas aqueous 
extracts of Lepiota americana retain their activit}^ for weeks or even 
months ( see Kastle 238 ) , and glycerin extracts of Lactarius piperatus 
and Lactarius volumen were found by Kastle to blue guaiaeum four 
years after they were first prepared. 
Reference has already been made to the fact that aqueous extracts 
of laccase have been found to lose their activity on boiling. It has 
also been pointed out that laccase is less sensitive toward heat than 
tyrosinase. That it has a rather high thermal death point as com- 
pared with certain other ferments may be seen from the following 
observations bearing on this point. Kastle ( 238 ) found that exposure 
to a temperature of 80° C. or higher for a short time is sufficient to 
render the very active oxidases of Lepiota americana inert. On the 
other hand, at temperatures below 80° C. an hour's exposure was 
found to be insufficient to destroy the oxidizing power of these ex- 
tracts toward guaiaeum. Bertrand (cited by Green ( 199 ), p. 293) 
found laccase to be still active after heating to 70° C. 
As already pointed out (see pp. 59-61), laccase is not specific in its ac- 
tion, but promotes the oxidation of a large number of easily oxidizable 
substances, such as guaiaeum, guaiacol, phenolphthalin. hydroqui- 
none, pyrogallol, adrenalin, and many other phenols and amino 
derivatives of the benzene series. 
It has long been known that such substances as hydrocyanic acid 
and hydrogen sulfide destroy the activity of the oxidases and similar 
catalysts. Bouffard (° 9, 70 ) has pointed out that sulfurous acid pre- 
vents the action of oenoxydase. Up to the present, however, very 
little systematic work has been done on the effect of poisons on laccase. 
Kastle and Loevenliart ( 244 ) observed that the oxidizing power of 
aqueous extracts of the potato is destroyed by hydrocyanic acid, 
hydroxylamin, phenylhydrazin, sodium thiosulfate, and tenth-nor- 
mal solutions of certain acids, such as hydrochloric, hydrobromic, 
benzene-sulfonic, para-nitro-toluene-sulfonic, oxalic, and salicylic, 
and that these substances also inhibited the oxidizing power of certain 
organic peroxides. Recently Bertrand ( 6l ) has found that most acids 
exert a poisonous or paralyzing action on laccase. On the other 
hand, there are some acids, such as carbonic, boric, and phosphoric, 
which are inactive at all concentrations. 
THE PREPARATION OF LACCASE. 
Slowtzoff ( 404 ), using the potato and cabbage as sources of the 
ferment, employed the following method for the preparation of 
what he calls pure laccase: One kilogram of fresh-washed potatoes 
were macerated to a paste and acetic acid added, so as to form a 0.5 - 
