750 
Journal o f Agricultural Research 
Vol. XXXI, No. 8 
As a fumigant for weevil-infested wheat and flour, chloropicrin has 
been used to some extent, but previous observations as to its effects 
on these materials have been of general nature and hence it seemed 
desirable to undertake a more critical study. Moore (16) observed 
that chloropicrin had some effect on bread prepared from chloro- 
picrin-fumigated flours. His data tended to show that yeast activity 
was retarded in the fermenting dough, and that the gluten was 
affected to some extent, for he noted that the texture of the bread 
baked from treated flours was slightly inferior to that made from 
untreated flour. 
Ryo Yamamoto (22) stated that when chloropicrin was sprayed 
into a storehouse used for rice and wheat, noxious insects were killed 
without bad effects on the cereals. That the fumigant had consider¬ 
able penetrating ability is indicated by the fact that it killed pupae in 
cocoons. Piutti (17) stated that chloropicrin gave excellent results 
in killing insects with no injurious effects on wheat, flour, or bread. 
Bertrand and Rosenblatt (4, 9) found that very small amounts of 
chloropicrin retarded and even inhibited enzyme action in general and 
fermentation in particular. It seems to the writers that this retarda¬ 
tion of zymase activity is of importance in bread making. 
EFFECT OF YEAST ACTIVITY 
Bertrand and Rosenblatt (9) presented data which showed that 6 
milligrams of chloropicrin completely inactivated zymase in a liter 
of the stock yeast suspension which they were using. These workers 
measured the activity of the enzyme in terms of sucrose which 
disappeared from the medium. 
The manifest function of yeast in bread making is the production 
of carbon-dioxide gas and aeration of the dough. In this work, the 
carbon dioxide produced in unit time rather than the percentage of 
sucrose which was fermented was taken as the measure of yeast 
activity. A stock solution was prepared containing the following 
materials: 1,000 c. c. water, 30 gms. yeast, 100 gms. sucrose, and a 
trace of dibasic ammonium phosphate. To 50 c. c. aliquots of this 
solution were added varying quantities of aqueous saturated chloro¬ 
picrin solution, as shown in Table I and II. This aqueous chloro¬ 
picrin solution was in contact with liquid chloropicrin at 18° C., and 
as chloropicrin is soluble in water to the extent of 1.65 gms. per liter 
at this temperature, each cubic centimeter of aqueous chloropicrin 
solution contains 1.65 mgms. of chloropicrin. Portions of the sus¬ 
pensions containing the several quantities of chloropicrin were placed 
in fermentation tubes, and the quantity of carbon dioxide read at 
hourly intervals. The relative quantities of carbon dioxide are given 
in millimeters of tube length, the fermentation tubes not being 
graduated. The fermentation was carried on at 28° C. 
It was thought desirable in practical fumigation to use a solution 
of equal quantities of carbon tetrachloride and chloropicrin. Such a 
solution was prepared, and to it was added distilled water. Quantities 
of this aqueous carbon tetrachloride-chloropicrin solution were added 
to 50 c. c. aliquots of the stock yeast solution. The results are given 
in Table II. 
