hate eo: oo 
1913] HAWKINS—MALT DIASTASE 271 
no alteration in the starch could be detected by the iodine test, 
after a peed of 5 hours in the water-bath. 
Ad tion of the resistances of the starch and diastase 
solutions by means of a Wheatstone bridge and the calcula- 
tion of corresponding conductivities showed the presence of a 
small quantity of electrolytes in the mixture. These must have 
modified to: some extent the effect of the addition of the 
different salts in the experiments. Since, however, the same con- 
centrations of starch and diastase were employed throughout the 
investigation, the electrolytes originally present are to be considered 
as constant in quantity. Furthermore, the concentrations of the 
salts used were usually comparatively high, so that any resulting 
errors due to what may be termed electrolytes of impurity (or of 
constitution) of the mixture used must be relatively slight. 
It was observed in many cases that, in mixtures containing salts 
at the higher concentrations used, a flocculent precipitate was 
gradually formed during the experiment. This precipitate was 
isolated and gave no starch reaction with iodine. No relation 
could be detected between its occurrence or amount and the diastatic 
activity. It seems, therefore, that the effect of the presence of a 
salt in increasing or decreasing diastatic activity cannot be due to 
a salting out from the solution of either diastase or starch. This 
is in accord with the conclusion reached by Core” in his work on 
ptyalin, but contrary to what might seem to be the case from the 
investigations of Harpy.’?7 In this connection it is interesting to 
note that Munrer®™ has recently shown that many of the salts of 
the alkalies and alkaline earths are ineffective for the precipitation 
of the diastase of Aspergillus oryzae. 
Testing was begun when the mixtures had remained in the water-_ 
bath one hour, and was continued thereafter at intervals of 15 
minutes until the conclusion of the experiment. Thirty or more 
LE, S. W., Contributions to our knowledge of the action of enzymes. Part I 
The influence of electrolytes on the action of amylolytic ferments. Jour. Physiol. 
30: 202~220. I 
™ Harpy, W. B., A preliminary investigation of the conditions which determine 
the stability of seca hydrosols. Proc. Roy. Soc. London 66:110-125. 1900. 
8 Munter, F., Uber Enzyme. Landwirtsch. Jahrb. Erganzband III. 39:298- 
314, 1910. ; 
