480 ANNUAL. REPORTS OF DEPARTMENT OF AGRICULTURE. 



with the Bureau of Entomology, to determine the efficiency of sodium 

 cyanid as a substitute for potassium cyanid in fumigating operations; 

 the proper proportion of cyanid, acid, and water to be used to obtain 

 the greatest yield of hydrocyanic-acid gas, and the effect that im- 

 purities in the cyanid, principally chlorids, will have on the reaction. 

 This work has been completed, and the results are of no small eco- 

 nomic value. 



The investigations of lead arsenate, begun in 1907 in cooperation 

 with the same Bureau, have been published as Bulletin 131 of the 

 Bureau of Chemistry. The examination of 50 samples of lead arsen- 

 ates found upon the market are given, together with directions for 

 preparing homemade lead arsenate, the chemical examination of 

 the materials from which it is prepared, and the observed effects of 

 different lead arsenates and the impurities they may contain on peach 

 foliage. Results of importance were obtained, and the work is being 

 further continued. Orchard tests are being conducted with numerous 

 poisonous materials which have sugegsted themselves as of possible 

 value as insecticides, with the hope of discovering some compound 

 which may be used on peach and other tender foliage without causing 

 injury thereto. 



Another investigation, begun last year in cooperation with the ento- 

 mologist, on the toxic effect on orchards of certain elements, notably 

 copper and arsenic, which may accumulate in the soil as a result of 

 spraying, is still under way. This will require the examination of 

 many orchards before any definite conclusions can be drawn. 



On account of the increasing interest in the subject of insecticides, 

 more accurate and detailed methods for their examination are de- 

 manded, manufacturers in particular being especially interested at 

 this time in this subject, owing to the recent passage of a national 

 insecticide law in regard to the inspection of insecticides and fungi- 

 cides. Much time has been devoted to this subject, particularly as 

 concerns methods for the analysis of the comparatively new and 

 important insecticides, lead arsenates. This work and that in con- 

 nection with the orchard experiments have required during the year 

 approximately 500 determinations which do not appear in the tabu- 

 lation. 



Cattle feeds and grains. — The total number of samples examined 

 in the laboratory studying these materials was 743, including sam- 

 ples of cattle and poultry food and remedies, both foreign and do- 

 mestic, examined under the provisions of the food law, as well as 

 samples examined in connection with the study of such economic 

 problems as the feeding value of forage crops, the composition and 

 value of various grains and cereals and of their milling quality, and 

 of improved methods of examining such materials. 



Some time was spent in the study of methods for the determina- 

 tion of starch and sugars in cattle foods, requiring approximately 

 1,000 determinations, a special study being made of the cause of 

 varj'ing results obtained in the starch determinations in cotton-seed 

 meal. An improvement of the apparatus for fat extractions was 

 also devised. 



Of the 497 interstate samples of cattle foods and grains examined 

 125 were found to be illegal. The 233 miscellaneous samples ana- 

 lyzed were received principally from other bureaus of the Department. 



