EFFECT OF STORAGE, HEAT, AND MOISTURE ON PYRETHRUM 5 
In connection with the deterioration ©f unground flower heads, it 
is of interest to note that, in the 1912 tests, practically no difference 
in effectiveness was found between the 1908, 1909, and 1910 crops, 
which indicates that the flower heads are not noticeably injured in 
four years under the commercial conditions of storage. 
EFFECT OF SOAKING IN HOT OR COLD WATER 
Table V shows the effectiveness against roaches of pyrethrum pow- 
der which had been soaked for 24 hours in hot or cold water. 
Table V. — Effectiveness against roaches of pyrethrum powder soaked for 
hot or cold water. Ten roaches dipped in each test 
hours in 
No. 
Treatment. 
Hours required to kill. 
First roach. 
Last roach. 
Average. 
1 
Check, untreated 
21.7 
21.9 
12.5 
35.9 
48.2 
25.9 
? 
38. Q 
3 
Soaked in hot water 
hours. 
1 Probably injured in dipping. 
The material used in test No. 1 was prepared by soaking 20 grams 
of pyrethrum powder (80 mesh) in 100 c. c. of cold water for 24 hours. 
The water was then filtered off and the powder dried at room tem- 
perature and resifted to 80 mesh. 
The material used in test No. 2 was prepared in the same way, 
boiling water being used. 
This table shows that pyrethrum soaked for 24 hours in cold water 
killed all of the dipped roaches in 48.2 hours, but required on the 
average 13 hours longer to kill than did the untreated powder. The 
pyrethrum treated with hot water killed only 9 roaches in 94 hours. 
It is therefore evident that cold water removes some of the active 
ingredients from pyrethrum powder, but not as much as is removed 
by hot water. 
EFFECT OF EXPOSURE TO DRY HEAT 
Table VI shows the effect on ground flower heads of exposure to 
dry heat for 18 hours. 
Table VI. 
-Effectiveness against roaches of pyrethrum powder exposed to dry heat for 
18 hours. Ten roaches dipped in each test 
No. 
Temperature. 
Hours required to kill. 
First roach. 
Last roach. 
Average. 
1 
Check, unheated 
20.5 
19.6 
• 21.1 
39.6 
43.6 
47.4 
31.0 
? 
120° C 
30.9 
3 
120° C 
27. X 
4 
130° C 
1 dead in 48 hours. 
5 
140° C 
