CHEMISTRY — BAXTER. I9I 



washed and dried at 250° in a current of dry air. Then after being weighed, 

 it was analyzed, either by heating in a quartz tube in a current of pure hydro- 

 chloric-acid gas until all arsenic had been expelled, or by solution in nitric 

 acid and precipitation with either hydrochloric or hydrobromic acid. All 

 three methods gave essentially the same results. A slight amount of residue 

 insoluble in dilute nitric acid was found to have essentially the same propor- 

 tion of silver as the arsenate itself. Since the residue was dissolved in more 

 concentrated acid before precipitation of the silver halides, no correction for 

 the residue is necessary. The proportion of water in the dried salt was 

 found by fusing weighed amounts of the salt in a current of dry air and 

 collecting the water set free in a weighed phosphorus pentoxide tube. After 

 applying a small correction found by blank experiments with the apparatus, 

 the proportion of water was determined to be 0.0056 per cent. Silver ar- 

 senate made from tri-sodic arsenate contains a slightly higher percentage of 

 silver than material made from other di- and tri-arsenates of sodium and 

 ammonium. On account of the distinctly basic nature of tri-sodic arsenate, 

 it is probable that the silver salt made from it contains basic impurity. Hence 

 the results from this material were not considered of value and are omitted 

 in the following table. Silver is assumed to have the atomic weight 107.88. 



The results of this investigation are being published in the Proceedings of 

 the American Academy of Arts and Sciences. Work is under way on the 

 ratio of arsenic trioxide to iodine and iodine pentoxide. 



It has not been possible to complete the analysis of silver phosphate which 

 was begun last year by Dr. Grinnell Jones. This investigation will, however, 

 be continued in the near future. The atomic weight of phosphorus was fur- 

 ther investigated by Mr. A. C. Boylston, who undertook first the analysis of 

 phosphonium bromide. This substance, owing to its unstable nature, was 

 found unsuitable for exact work. Phosphorus tribromide was next selected 

 for investigation and a method for preparing the tribromide in a pure state in 

 the absence of moisture was devised. Unfortunately the serious illness of 

 Mr. Boylston interrupted this research before any conclusive analytical re- 

 sults had been obtained. This investigation will be continued during the 

 coming year. 



