BUREAU OF CHEMISTRY. 459 



NITROGEN WORK. 



A laboratory is especially equipped for determining nitrogen and 

 to it are referred all samples on which this determination is to be 

 made. A total of 12,077 such analyses were made in the past fiscal 

 year, the samples being referred not only from the laboratories of 

 this bureau but from other bureaus of this department and also 

 from other departments, as follows: 



Department of Agriculture: 



Bureau of Plant Industry 650 



Bureau of Soils 30 



Bureau of Animal Industry 2 



Office of Experiment Stations 2 



Bureau of Forestry 6 



General Supply Committee 3 



War Department 8 



Istlunian Canal Commission 4 



Navy Department 6 



Treasury Department, Bureau of Engraving and Printing 12 



Total 729 



The laboratory has also continued to collaborate with other 

 nitrogen chemists in studies for the improvement of the present 

 methods of analysis. 



SPECIAL RESEARCH WORK. 

 ANIMAL PHYSIOLOGICAL CHEMISTRY, 



The work on the deterioration of meat and fish was continued and 

 extended to include an examination of a large number of inspection 

 samples of liquid and dried eggs and different brands of canned 

 salmon and sardines to determine evidences of deterioration and 

 decomposition. In this connection cooking tests were made on fish 

 and chicken in which fresh specimens and the samples in question 

 were prepared for the table in exactly the same manner and sub- 

 mitted to a committee for an organoleptic test. In all cases the 

 majority of the jurors could detect the aged and inferior product. 



Progress has been made in the collection and analysis of the 

 various brands of infant foods now on the market. About 30 differ- 

 ent brands have been collected and their analyses partly completed. 

 Feeding experiments on mice and kittens have been conducted with 

 each of the different brands being prepared, for feeding, according 

 to the formulae prescribed in the accompanying directions. In 

 some cases several modifications have been tried. The data obtained 

 are being collated. 



Among the miscellaneous problems referred to tliis laboratory 

 were the following: A feeding experiment on rabbits, using solutions 

 of different strengths of calcium hyperchlorite, was conducted in 

 collaboration with the water laboratory of the miscellaneous division. 

 This investigation and that of other chemical agents used in the 

 purification of water supplies will be continued during the coming 

 year. 



The question of the solubility of the silver coating on candy in 

 the digestive juices was studied. Saliva, artificial gastric juice, and 



