INSECT POWDER. 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.^ 



Ash. — Four or five grams of the sample were weighed into a plat- 

 inum dish and slowly heated in an electric mufiBe 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 insoluhle in ECl {"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 



1 Jour. A. O. A. C, Vol. 1, No. 4, Pt. II, p. 7. 



