264 Raymond FH. Pond. 
hardly be assumed that the addition of acid or of alkali even in 
completely dissociated condition does not alter the toxicity of the 
reagent. Since the activity of the enzyme varies with acidity, with 
alkalinity, with temperature, etc., it is more important to maintain 
uniform conditions with disturbing factors reduced to a minimum 
than to establish certain optimum conditions with such factors 
present. The temperature of 40° C. was selected for all the experi- 
ments. The actual concentration of the enzyme was not known. 
The following was the procedure in the preparation of the colloidal 
solution of the enzyme. One tenth of a gram of the enzyme powder 
was triturated with a little water and diluted to 100c¢.c. This was 
filtered from a small residue which was discarded with the filter. Of 
this filtrate 50 c.c. were diluted to 200 c.c. Then of this volume 2 c.c 
Were pipetted to each vial which already contained 2 c.c. of the toxic 
agent or of distilled water. If all the powder had dissolved, and if 
the powder had been dry at the beginning, the concentration of the 
enzyme ready for incubation would have been 0.0125 per cent. It 
must, of course, have been less than that. The concentration of the 
enzyme solution, when boiled, was 0.025 per cent. There was no 
flocculation. After the incubation there was sediment in only one 
Case, mercury, 
RELATIVE TOXICITY WITH THE CONCENTRATIONS 
OF ENZYME THE SAME, 
Sodium, lithium, and potassium in contemporaneous test. — The 
figures in the tables which follow express the quantity in c.c. of M- 
20 KOH required for the neutralization of the liquid in each individ- 
ual vial at the close of the incubation period. If the acidity of the 
three individuals of a given group varied, the average was taken. If 
More than one was wrong, the test was repeated. As a rule only 
very trivial variation appeared. In the column headed “ M” is given 
the concentration of the toxic salt, present during the incubation, in 
terms of fractional molecular concentration. Thus 64 in the column 
headed ““M” means a concentration of one sixty-fourth molecular. 
The word “Water” in this column means that 2 c.c. of distilled 
water replaced the 2 c.c. of the toxic salt, so that the uninhibited 
activity of the enzyme is shown. The column headed “ Reagent” 
Shows the initial acidity of 4.c.c. of the toxic salt solution of the 
Concentration indicated by the corresponding figures in the column 
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