: INSECT POWDER 39 
compared with those in the stems. Upon these two constituents 
therefore the most stress is laid. Although the active insecticidal 
principles are soluble in ether and certain other organic solvents, the 
efficiency of the product can not be measured by the quantity of this 
ether extract as now determined, because some inactive constituents 
are also soluble in ether and many of the purest samples show an 
ether extract content lower than that of some which are seriously 
adulterated. The color of the ether extract, which should be 
observed before evaporating oft the ether, is of more value than the 
quantity in determining the purity of the powder. It should be 
yellow, with no more than a slight tinge of green. 
The chemical composition of a number of genuine samples of 
Pyrethrum flowers and stems was studied. Most of the samples 
were the Chrysanthemum cinerariefolium, the species now commonly 
used in the United States for the production of insect powder. The 
three grades of flowers recognized by the trade, namely, “open,” 
““half-open” (‘‘half-closed’’), and ‘closed,’ were obtained. Sam- 
ples of the commercial flowers, consisting of from 1 to 2 pounds of 
material, were obtained, and the percentage amounts of stems and 
dirt Gncluding all matter other than flowers or stems) present were 
first determined. From the commercial samples of Pyrethrum stems 
_ the burrs, straw, and other foreign matter were removed and classified 
as “‘dirt.’”” In each case 100 grams of the material, selected so as to 
accurately represent the whole sample, was used, and the separa- 
tions were carefully made by hand. After separation of the ex- 
traneous material the flowers and stems were each ground to a 
powder for chemical analysis. (Owing to the small quantity of 
“dirt”? and stems in the commercial flowers and to the small quan- 
tity of dirt in the stems, it was found that these had little influence 
on the composition of the stems and flowers. The removal of this 
extraneous matter was therefore discontinued.) 
Metuops or ANALYSIS 
Moisture.—Two grams of powder was weighed into an aluminum 
dish provided with a tight-fitting cover, and dried to constant 
weight in an oven heated by boiling water, an vacuo. When cooling 
in the desiccator and when weighing, the dishes were kept covered, so 
that the powder could not absorb any moisture from the air. It was 
found necessary to heat the powder from 8 to 10 hours before constant 
weight was reached. The loss in weight was reported as moisture. 
Nitrogen.—This was determined in 2 grams of powder according 
to the official Gunning method.* 
Ash.—Four or five grams of the sample was weighed into a plat- 
inum dish and Bete lieated in an electric muffle furnace, finally at 
a dull red heat, until all the carbon was consumed. The residue was 
reported as ash. In practically all published methods for the deter- 
mination of ash in insect powder, it is stated that the powder is 
simply ignited to constant weight. Such a method might give erro- 
neous results, owing to the presence of volatile potassium salts in 
Pyrethrum, which would be lost; also, ignition in the presence of 
organic matter would reduce phosphates. By using an electric 
muffle furnace all the carbon is consumed at a dull red heat ; hence, 
these losses are practically prevented. 
5 Methods of Analysis, A. O. A. C., 2ed., 1925, p. 8. 
