INSECT POWDEK. 47 
recognized by the trade, namely, "open," "half-open" ("half- 
closed"), and "closed," were secured. Samples of the commercial 
flowers, consisting of from 1 to 2 pounds of material, were obtained, 
and the percentage amounts of stems and dirt (including 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, were used, and the separations were 
carefully made by hand. After separation of the extraneous ma- 
terial 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 amount of dirt in 
the stems, it was found that these had little influence on the com- 
position of the stems and flowers. The removal of this extraneous 
matter was therefore discontinued.) 
Methods of Analysis. 
Moisture. — Two grams of powder were weighed into an aluminum 
dish provided with a tight-fitting cover, and dried to constant 
weight in an oven heated by boiling water, in 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. 1 
Ash. — Four or five grams of the sample were weighed into a plat- 
inum dish and slowly heated 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, due 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. 
Ash insoluble in HCl (" sand"). — The residue from the ash deter- 
mination was transferred to a beaker, and digested with dilute hydro- 
chloric acid (water 100 cc, HCl, sp. gr. 1.19, 15 cc.) for 2 hours on 
the steam bath, then filtered, washed, and the residue ignited and 
i Jour. A. O. A. C, Vol. 1, No. 4, Pt. II, p. 7. 
