INSECTICIDE AND FUNGICIDE BOARD. 427 



SPECIAL INVESTIGATIONS. 



The investigation begun some time ago to discover a chemical 

 method of determining stems in insect powder, determine reasonable 

 standards for insect powder, and study the process of manufacture 

 of insect powder and composition of raw materials as well as the 

 finished product has been completed and the data for a report col- 

 lected. The data include statistics of the insect-powder industry, 

 early history, cultivation and harvesting of the flowers, preparation 

 of the powder, its use as an insecticide, common methods of adultera- 

 tion, and a review of the physiological and chemical methods for 

 examining insect powder. A method has been devised for the quanti- 

 tative determination of powdered stems in insect powder, which is 

 of great importance in that it enables the board to determine 

 whether or not the insect powder sold on the American market is 

 adulterated with stems. Results of chemical anal3'Ses of several 

 hundred authentic samples of insect flowers, stems, and powders 

 are given, on the basis of which standards for allowable amounts 

 of sand and stems in insect powder have been determined and pre- 

 pared for issuance in the Service and Regulatory Announcements of 

 the board. 



A paper was published in the Journal of Agricultural Research, 

 for October, 1917, entitled, " The Occurrence of Manganese in 

 Chrysanthemum Cinerariaefolium." In this paper it is shown that 

 the presence or absence of manganese in insect powder is of no 

 value in determining its genuineness or purity, as has been claimed 

 by previous writers, that if the plants are grown in a soil containing 

 manganese the flowers as well as the stems will contain manganese, 

 and that, of course, in the absence of manganese in the soil it will not 

 be present in either the stem or flowers. 



A paper prepared by a chemist of the board in collaboration with 

 the Bureau of Chemistry, entitled, " The Decomposition of Di-Lead 

 Arsenate by Water," was published in the Journal of the American 

 Chemical Society for September, 1917. It is shown in this paper that 

 water decomposes di-lead arsenate, with the liberation of arsenic acid. 

 Equilibrium is reached when the concentration of the arsenic acid is 

 very low, but if the water is constantly replaced by pure water the 

 action proceeds until about 40 per cent of the total arsenic oxid goes 

 into solution and the residue is converted to a basic arsenate. The 

 results are of practical importance as showing what may take place 

 when di-lead arsenate is applied to foliage and acted upon by rain, 

 fog, dew, etc. 



During the last two years one of the chemists of the board, in col- 

 laboration with the Bureau of Chemistry, has made investigations to 

 determine how calcium arsenates sold in American commerce should 

 be labeled and to obtain scientific information relative to the prepara- 

 tion and properties of the various calcium arsenates. The ciiemical 

 work along this line is practically completed and scientific papers on 

 the subject will be published. As a result of this work, the board was 

 able to supply the Bureau of Chemistry with the basic information 

 for an investigation of the preparation of calcium arsenate under 

 commercial conditions. Also, as a result of this work, the board was 

 able to supply the Bureau of Chemistry with basic information on 

 which to prepare the calcium arsenates used in the project entitled, 



