BAXTER AND JONES. 



ATOMIC WEIGHT OF PHOSPHORUS. 



155 



The Specific Gravity of Silver Phosphate. 



In order that the apparent weight of the silver phosphate might be 

 corrected to the vacuum standard, the specific gravity of this salt was 

 found by determining the weight of toluol displaced by a known quan- 

 tity of salt. The specific gravity of the toluol at 25° referred to water 

 at 4° was 0.8633. Great care was taken to remove air from the salt 

 when covered with the toluol by warming the pycnometer, then placing 

 it in a vacuum desiccator and boiling the toluol under reduced pres- 

 sure. The salt and toluol were mechanically stirred to assist the 

 escape of air bubbles. This process was repeated several times. 



Therefore the apparent weight of silver phosphate was corrected to the 

 vacuum standard by adding 0.000044 gram per gram of salt. Similarly 

 0.000041 gram was added for every gram of silver bromide. 



The Adsorption of Air by Silver Phosphate. 



Since the silver phosphate was in a very finely divided condition 

 and since many fine powders have the power of adsorbing appreciable 

 quantities of air or other gases, the possibility of the adsorption of air 

 by silver phosphate was investigated. The method of experimenting 

 and the apparatus were very similar to that used by Baxter and Tilley 

 for investigating the behavior of iodine pentoxide. 



" Two weighing bottles were constructed with long, very well ground 

 stoppers which terminated in stop-cocks through which the tubes could 

 be exhausted. These tubes were very closely of the same weight and 

 very nearly the same internal capacity. The tubes were first exhausted 

 and compared in weight by substitution. Next they were filled with 

 dry air and again weighed, the weighing being carried out with stop- 

 cocks open. Both steps were then repeated with essentially the same 

 results." 27 



" Baxter and Tilley, Jour. Amer. Chem. Soc, 1909, 31, 214. 



