44 



BULLETIN 824, U. S. DEPAKTMENT OF AGRICULTUEE. 



Table 21. — Chemical analysis of pure 



insect powder 



and stem 'powder [Siedler). 







Determination. 



Product. 



Moisture 

 at 110°. 



Ash on air- 

 dried material. 



Ether 

 extract. 



Pure insect powder 



Per cent. 

 10.77 



Per cent. 

 6. 81 to 7. 29 



Per cent. 



Powder from best flowers 



6.14 



Stem powder 



8.69 



6.39 

 6.36 



1 48 



Unpowdered, but finely-cut flowers 











Siedler used ether with a specific gravity of 0.720, and, after com- 

 pletely extracting the sample in the cold, allowed the ether to evap- 

 orate spontaneously, and dried the residue for one hour upon the water 

 bath. The color of the extract of the powdered flowers was dirty 

 yellow, that of the stem powder green. With concentrated sul- 

 phuric acid there was no characteristic color reaction with either 

 resinous residue. Siedler found the petroleum-ether extract of 

 pure powdered flowers to be 4.01 per cent, and that of stem powder, 

 1.01 per cent. The flower extract was a pure yellow, that of the 

 stems a pure green. With concentrated sulphuric acid the petro- 

 leum-ether extract from the flowers gave a deep green color, the stem 

 powder a brown. He attempted to obtain a basis for analysis by 

 means of the optical behavior of an alcoholic extract from flower 

 and stem powders, but this extract proved to be optically inactive. 



In 1913 Siedler (257) commented as follows on the chemical exami- 

 nation of insect powder: 



As the best criterion for the value of the insect powder ia the determination of 

 the ether extract, which was first made by Thoms. Later this method was modified 

 in this way, that the powder was shaken with ether and an aliquot part of the decanted 

 ether solution allowed to evaporate. This procedure has certain drawbacks. It is 

 not possible to decant a definite quantity of ether solution without causing a difference 

 in weight by evaporation of ether. Further, the ether solution can not be obtained 

 clear except after long standing aijd it is very difficult to filter clearly. It always 

 deposits fine dust after filtration. Finally, there is generally the feeling that the 

 powder is not completely extracted through simple shaking, that a part of the ether- 

 extractable material escapes determination. 



In the same article Siedler gives results for the determination of 

 ash in insect powders (Table 22). All these samples were ground 

 from the best flowers free from stems, and had an average moisture 

 content of 4 per cent. The total ash and the ash insoluble in dilute 

 hydrochloric acid were determined on 2.5 grams of substance. 

 Table 22. — Determination of ash in insect powder (Siedler). 



Sample No. 



Total. 



Insolu- 

 ble in 

 HCl. 



Sample No. 



Total. 



Insolu- 

 ble in 

 HCl. 



1.... 

 2.... 

 3 





Per cent. 

 8.6 

 7.7 

 7.0 

 7.0 

 7.9 



Per cent. 

 0.1 

 .1 

 .2 

 .2 

 .1 



6 



7 



8 



Per cent. 

 8.0 

 7.9 



7.7 

 7.8 

 6.8 



Per cent. 

 0.1 



4 



9 





5.... 



10 





