CHEMISTRY — BAXTER. 



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Baxter, Gregory P., Harvard University, Cambridge, Massachusetts. Grant 

 No. 691. Determination of atomic weights. (For previous reports see 

 Year Books Nos. 3-9.) $1,000 



With the assistance of the above grant the following researches were car- 

 ried on under Professor Baxter's direction: 



The analysis of phosphorus tribromide has been completed by Dr. C. J. 

 Moore (for previous reports on this research see Year Books Nos. 7, 8, and 

 9). The preparation of this substance by the union of dry phosphorus and 

 bromine in a vacuum and subsequent fractional distillation, and the analysis 

 of the separate fractions for bromine by precipitation, as silver bromide, 

 have already been described in Year Book No. 9. Three series of samples 

 were collected by fractional distillation of three different preparations. Of 

 these the third was distilled over metallic silver. In the following tables of 

 results a higher number indicates an earlier fraction, while the lowest number 

 represents essentially residual material. The atomic weight of silver is 

 assumed to be 107.88. 



The different fractions of the same preparation in every case yield results 

 so nearly identical that it seems reasonably certain on the one hand that the 

 slight excess of bromine used in the synthesis of the tribromide was elimi- 

 nated during the early stages of the fractional distillation, and on the other 

 hand that there was no appreciable decomposition of the tribromide even in 



