60 KELLERMAN: EFFECTS OF CHEMICAL AGENTS 
slight inhibition. At a dilution of /10,000 there was a slight 
acceleration with hydrochloric and nitric acids, and none with the 
others. Malt diastase requires a 2/500 dilution before any starch 
is converted, and at 7#/1,000 requires nearly 12 c.c. to reduce the 
2 c.c. of Fehling’s solution. Acceleration does not set in until a 
dilution of nearly 7/5,000 is reached. 
Among the organic acids, Detmer* for citric, Krauch } for 
salicylic, and Kjeldahl ¢ for lactic, butyric, formic, salicylic, acetic 
and others, record an acceleration for weak dilutions of the 
acids. § 
* Detmer, Zeitschrift fiir physiologische Chemie, 7: ie 
~ f— Krauch, Landwirtschaftliche Versuchstation, 23 : 77. 
t Kjeldahl, Zeitschrift fiir das gesammte Brauwesen, 3: 179. 1880. 
% In this connection, perhaps Dr. Leffmann’s paper, ‘‘ Digestive Ferments with 
Especial Reference to the Effects of Food Preservatives’? (Journal of the Franklin 
Institute, 147: 97), should be mentioned. 
Dr. Leffmann was working merely to find what antiseptics were injurious to enzy- 
metic action, and records only inhibitory effect. He used only the iodine test to deter- 
mine the presence of unconverted starch and dextrines, and hence it is impossible to 
accurately compare his results with mine. It seems, however, that in his experiments 
with taka diastase, tartaric and citric acids gave a decided inhibition, while in my 
work, at supposedly corresponding concentrations these acids were almost without 
effect. 
It will be seen on the other hand that he notes no injurious action due to formalin, 
using 3 c.c. of formalin and, as far as I can gather from his paper, 50 c.c. of 1 per cent. 
starch. This corresponds to about 2/3 formalin, which, as will be seen Jater in my 
paper, I find to be very injurious indeed. This brings out the fact that the iodine test 
is entirely inadequate for determinations where formalin is present. If pure starch solu- 
tion in the presence of formalin is allowed to stand a few hours, it will give a dextrine 
reaction, and if the action is allowed to continue twelve to twenty-four hours, or if the 
starch and formalin are boiled together, no starch or dextrine color reaction can be ob- 
tained with iodine. Yet if these solutions are treated with NH,OH to break the for- 
malin down to hexamethyleneamine (CH,,),N,, and any excess of ammonia neutralized, 
iodine will again give the typical starch blue, and Fehling’s will give no reaction. 
Now if the iodine is added immediately upon the addition of formalin to pure starch 
solution, so that the starch is colored blue, then the formalin does not affect the color 
even upon standing twenty-four hours; while if this blue starch solution containing 
formalin is boiled, it loses its color, even after cooling, and upon the addition of more 
iodine gives now the red, or so-called erythrodextrine reaction. The action of the 
formalin is upon the starch, for even if iodine and formalin have been boiled together, 
the iodine will produce as good a blue as before. 
These results hold both for starch paste and fresh starch ratte The latter show 
no difference under the microscope, even after a treatment with formalin sufficient to 
preclude their coloring with iodine. It seems to me, therefore, that formalin either 
has some physical action upon the starch or else forms some unstable compound, com- 
parable to the supposed starch-iodine compound to which is due the iat of the starch 
test, but being very much more unstable. 
