Solution Tension and T. oxuily tn Lipolysts. 267 
TARLE III. 
AMMONIUM. 
M. Increase. 
32 0.10 
16 0.05 
8 0.03 
> 0.00 
Water. 0.20 
Enzyme, 0.0125 percent. Incubation period, 4 hours. 40° C. 
The limit for ammonium is evidently at 4, and allowing for the fact 
that it is univalent makes it equal in toxicity with barium, strontium, 
and magnesium. All the preparations were water clear after diges- 
tion and free from sediment. On titration a precipitate did not 
appear at or near the neutral point, which is also true of the salts 
thus far tried, but is not true of some of those to be referred to 
presently. 
Cadmium, cobalt, and zinc in contemporaneous test. — Since in higher 
concentrations the solutions of these salts are acid, it seemed nec- 
essary to know the actual acidity of the plain salt solution for each 
dilution tried. In the table, therefore, there is the column headed 
“ Reagent,” which shows the acidity of 4 c.c. of the toxic salt . 
corresponding to the concentration indicated in the column headed 
““M.” It may be noted, as might be expected, that the acidity 
increases directly with the concentration. The acidity of the control 
does not vary with such precision. In this test the incubation period 
was lengthened, so that digestion could be going on during the night 
to save time. This was regarded as safe, since the salts are toxic 
enough to prevent any bacterial action during the incubation. But 
even granting some fermentation, which is very improbable, it would 
be equally distributed in the control and in the enzyme solution. 
a All the preparations were water clear and free from sediment after 
_ the incubation. On titration with alkali a precipitate appeared at the 
neutral point, or in some cases shortly before. The concentration 
. at which this precipitate first appeared agreed closely with that of 
the plain reagent showing the first trace of acidity. The plain 
reagent also throws down a precipitate at or nearly the same concen 
tration. The coincidence of these points was closer, the greater the 
dilution of the enzyme. 
* 
