INSECT POWDER. 21 



Miscellaneous adulterants — Continued . 

 Pepper. 



Quassia (wood of I'icrasmu cxcclsa (Swartz) Planchon; and of Quassia amara L.). 

 Quillaja, soap-bark (dried bark of (jiiillaja sapcmurlu INIolina, deprived of its 



periderm). 

 Sawdust. 

 Senna leaves (dried leaves of Cassia aruti/olia Delile; or of Cassia angustifolia 



Vahl.). 

 Starch, potato. 

 Starch, wheat. 



Starch, variety not specified. 

 Stems and leaves of insect powder plant. 

 Sumach (dried fruit of Rhus glabra L.). 



HOW TO DETECT ADULTERATION. 



The methods which have been used in determining the genuineness 

 of insect powders may be classified in 3 groups : 



1 . Physiological. — The powder to be tested is tried out directly on 

 one or more species of insects, and the time necessary to produce 

 death compared with the time in which the same quantity of a known 

 genuine insect powder will kill the insect. 



2. Microscopical. — ^Adulterants are detected by observation 

 through the microscope, either with or without staining or other 

 preliminary chemical treatment. 



3. Chemical. — The ash, ether extract, and other chemical deter- 

 minations are made and the results compared with the average values 

 for genuine powders. 



PHYSIOLOGICAL METHODS. 



Kalbruner (151), in 1874, was the first to record the physiolog- 

 cal testing of insect powder. He states that 4 grains of a good 

 insect powder sprinkled on a fly in a vial should produce stupor in 

 1 minute and death in 2 or 3 minutes. Testing a number of commer- 

 cial powders in this manner, he found that from 15 to 30 minutes 

 were required to kill flies. Flowers representing a number of 

 species of plants, as well as the powdered stems and leaves of Pyre- 

 thrum roseum and cinerarisefolium, were tested in this way, and 

 found to be quite worthless, as compared with genuine insect powder. 

 In 1876, De Bellesme (63), in his research on the active principle 

 of Pyrethrum, in order to show that its action was not the mechanical 

 one of closing the pores of an insect, sprinkled flies with insect powder 

 and also with powdered leaves, wood, and various other inert sub- 

 stances. Those sprinkled with the Pyrethrum powder were almost 

 dead after 1 hour, while those left for 10 hours in the inert powders 

 were uninjured. 



