106 ANNUAL REPOKTS OF DEPAKTMENT OF AGRICULTURE. 



that this product consists of variable mixtures of meta-, pyro-, and 

 ortho-j)hosphoric acids with varying amounts of sodium phosphate. 

 It also appeared that the reversion of the glacial acid occurred not 

 only in commercial brands but in pure meta-phosphoric acid made in 

 the laborator3^ Obviously an article of such variable composition 

 should not be used in manufacturing medicines or compounding 

 prescriptions. 



MISCELLANEOUS INVESTIGATIONS. 



Insecticides and fungicides. — The increase of the efficiency of 

 insecticides and fungicides with the control or decrease of the injury 

 done to the plant or tree by their application is constantly the subject 

 of study by the Bureaus of Chemistry, Entomology, and Plant Indus- 

 try working in cooperation. During the year eight studies of the 

 kind were made, one of the most important being for the purpose of 

 determining the efficiency of sodium cyanid as a substitute for potas- 

 sium cyanid in fumigating operations, the best proportions to be 

 employed in making the mixture, and the efTect of the impurities 

 present in the cyanid on the reaction. The results proved to be of 

 considerable economic value. Lead arsenate has been exhaustively 

 studied, including the examination of 50 commercial samples, direc- 

 tions for preparing this insecticide on the farm, the analyses of 

 the materials entering into its preparation, and observations on the 

 effect of lead arsenates and the impurities present on peach foliage. 

 Orchard tests with numerous poisonous materials are in progress. 



Trade wastes. — Chemical investigations of the nature and extent 

 of injury to agricultural interests and forests resulting from the 

 fumes, tailings, and other wastes from smelters have been made in 

 cooperation with the Department of Justice, the principal scenes of 

 the operations during the past year having been at Anaconda, Mont., 

 and Ducktown, Tenn. At the latter place plants have recently been 

 erected to condense the sulphur trioxid and dioxid fumes and manu- 

 facture sulphuric acid therefrom, thus converting an injurious waste 

 into a profitable by-product. This process has been made the sub- 

 ject of special study. The effect of copper salts on certain grain 

 crops was also investigated to determine the effect of tailings from 

 smelters on farm crops irrigated with water contaminated by such 

 wastes. 



Chemical work on plant physiology. — In the majority of 

 studies on plant physiology the effects produced by varying condi- 

 tions, the periodic changes in composition during the growth of the 

 plant, and the quality of the products yielded by the experiments 

 must be tested by chemical determinations. In collaboration with 

 the offices of the Bureau of Plant Industry, therefore, many such 

 studies are prosecuted, among which the following are of special 

 interest and utihty: Acidity studies of peat to determine whether 



