BUREAU OF CHEMISTRY. 455 



An investigation begun two years ago relative to the toxic effect 

 of certain elements, notably copper and arsenic, wliich may accu- 

 mulate in the soil as the result of using compounds containing these 

 substances as sprays, is being continued. Samples of soils, foliage, 

 and parts of trees have been collected from widely distributed fruit- 

 growing areas and chemical analyses are being made thereof. 



Studies of methods of analysis in cooperation with other official 

 chemists have been engaged in during the year, and these, with other 

 miscellaneous work, have required about 600 determinations, making 

 the total number of determinations made in the laboratory for the 

 year approximately 7,000. 



The laboratory has been enlarged and the force of chemists mate- 

 rially increased during the latter part of the year in preparation for 

 the enforcement of the insecticide act, which work is now in progress. 



CATTLE FEEDS AND GRAINS. 



The total number of samples examined in the laboratory studying 

 these materials was 891, necessitating about 6,000 determinations 

 and including samples of cattle and poultry foods, both foreign and 

 domestic, examined under the provisions of the food law, and samples 

 analyzed in connection with tne study of such economic problems as 

 the feeding value of forage crops and the composition and value of 

 various grains and cereals, as well as of improved methods for exam- 

 ining such materials. 



The methods of determining crude fiber were studied and an 

 improvement made in the apparatus for determining pentosans, 

 which enables the analyst to get more accurate results with less 

 labor. The work on an improved fat-extraction apparatus was 

 continued this year and the results published in Circular 69 of this 

 bureau. 



Of the 500 interstate samples of cattle and poultry foods examined, 

 76 were found to be adulterated or misbranded. The distribution 

 of the total number of samples analyzed was as follows: 



Imported cattle foods and grains 4 



Domestic cattle foods and grains 500 



Miscellaneous cattle foods and grains 329 



Miscellaneous samples 58 



Total 891 



Distribution showing cooperative work: 



War Department 4 



Treasury Department 2 



Isthmian Canal Commission , 13 



Department of Agriculture: 



Bureau of Plant Industry 347 



Bureau of Forestry 3 



Bureau of Animal Industry 1 



Other laboratories of the Bureau of Chemistry 9 



Miscellaneous 8 



TRADE WASTES IN RELATION TO AGRICULTURE. 



This laboratory is organized for the purpose of studA'ing the effect 

 of trade wastes on agricultural products, on forests, and on cattle. 

 Particular attention has in the past been given to the study of the 

 effect of smelUr wastes on agricultural products, forests, animals, 

 and irrigation streams. This work has practically always been done 



