272 BOTANICAL GAZETTE [APRIL 
similar vials were prepared before each test, each with its drop 
of iodine solution, and the samples were consecutively pipetted 
into these from the tubes, following the order in which the diastase 
had been originally added. The pipette was thoroughly washed 
after each use and thoroughly clean vials were always employed. 
The number of minutes which elapsed before the end point was 
reached for each mixture was recorded, thus furnishing a means for 
the quantitative comparison of the enzyme activity under the differ- 
ent conditions. For example, a series of 2, 1/2, 1/8, 1/32, 1/128, 
1/512, and 1/2048 molecular sodium chloride gave for the respective 
TABLE I 
EFFICIENCY OF DIASTATIC ACTION AS AFFECTED BY VARIOUS CONCENTRATIONS OF 
s AND POTASSIUM CHLORIDES, SINGLY AND COMBINED 
SINGLE SALTS 
(Mol 1 pam ) 
ms I:I 
NaCl : KCl olecular proportio: 
Concentration . Concentration 4 Total salt con- : 
tk waetare Efficiency ta wieture Efficiency centration in Efficiency 
va 
2m <. 51 2m 1.77 
m/2 eg m/2 2.19 Mol. 1.38 
m/8 1.82 m/8 1.61 /4 1.93 
/32 1.42 /32 1.39 m/16 1.92 
m/128 0.85 m/128 0.85 /6 1.07 
m/512 0.95 m/512 0.93 m/256 0.89 
m/2048 I.02 m/2048 I.00 m/1024 0.96 
time periods 165, 165, 150, 180, 315, 285, and 300 minutes, the 
control mixture (without any added salt) reaching the end point 
in 285 minutes.’? The intensity of the enzyme action in experi- 
ments such as these is, of course, for any given mixture reciprocally 
proportional to the number of minutes required for that mixture 
to reach the end point. Thus the ratio of the time period of the 
control to that of any mixture is obviously a measure of the velocity 
of the hydrolysis for that mixture in terms of the velocity of the 
control. Thus, the relative velocities or intensities of starch hy- 
drolysis for the experiment just cited become, respectively, 285/165, 
19 The time periods for the two control tubes were the same in all series except 
- three, and in these cases the two results (differing but slightly) have been averaged. 
