266 Raymond H. Pond. 
corresponding ones in the column headed “Increase.” The same 
relation was found in this contemporaneous test of barium, strontium, 
and magnesium. To avoid repetition, the figures expressing “ In- 
crease” are alone indicated under the name of the corresponding 
metal. 
TABLE II. 
BARIUM, STRONTIUM, ANDe MAGNESIUM. 
M. Barium. Strontium. Magnesium. 
64 0.15 , 0.10 0.10 
ae 0.07 0.05 0.05 
16 0.03 0.03 0.05 
0.00 0.00 0.00 
Water = 0.20 
Enzyme, 0.0125 per cent. Incubation period, 4 hours. 40° C. 
All the preparations were water clear after digestion and free from 
sediment. Practically the same figures were obtained in a subse- 
quent test. These three salts are undoubtedly, under these con- 
ditions, practically equal in toxicity. 
he figure showing the uninhibited activity of the enzyme is 
identical with that obtained in the test given in Table I. In com- 
parison with sodium, lithium, and potassium these three are certainly 
More toxic, and upon an equimolecular basis the ratio is 1:4 the 
limit for the former is assumed to be M-2. 
Ammonium, — Since phenolthalin cannot be used in the case of 
ammonium, liquid litmus was used instead, being added of course after 
the incubation. In other respects the conditions were exactly the same 
as in the preceding test. To avoid error due to change of indicator, 
the barium test was repeated at the same time. The litmus was 
used in the place of the phenolthalin. The titration with litmus is 
not sharp, as is the case with phenolthalin, but in this test it happened 
that the figures for barium corresponded exactly with those obtained 
in the preceding test, so that it is unnecessary to repeat them. This 
means that the result with litmus in this case is just as satisfactory 
as with phenolthalin, and the figures for ammonium are strictly 
Comparable with those for barium and the rest. Since all the 
Controls were neutral and the reagents were also neutral in all 
dilutions of the test, only the figures showing the acidity developed 
during incubation are given. 
