ATOMIC WEIGHTS 303 



1.787 grm. PCl3 = 4.208 grm. Ag. 42.4667 



1.466 " 3.454 " 42.4435 



2.056 " 4.844 " 42.4443 



2.925 " 6.890 " 42.4528 



3.220 " 7.582 " 42.4690 



Mean, 42.4553, ± .0036 



Hence P = 31.027. 



By Van der Plaats ^ three methods of determination were adopted, 

 and all weights were reduced to a vacuum standard. First, silver was 

 precipitated from a solution of the sulphate by means of phosphorus. 

 The latter had been twice distilled in a current of nitrogen. The silver, 

 before weighing, was heated to redness. The phosphorus equivalent to 

 100 parts of silver is given in the third column : 



.9096 grm. P gave 15.8865 Ag. 5.7256 



.5832 " 10.1622 " 5.7389 



Mean, 5.7322, ± .0045 



Hence P = 30.930. 



The second method consisted in the analysis of silver phosphate; but 

 the process is not given. Van der Plaats states that it is difficult to be 

 sure of the purity of this salt. 



6.6300 grm. Ag^PO, gave 5.1250 Ag. 77.300 per cent. 



12.7170 ■' 9.8335 " 77.326 



Mean, 77.313, ± .0088 

 Hence P = 30.970. 



In the third set of determinations, yellow phosphorus was oxidized by 

 oxygen at reduced pressure, and the resulting PoO, was weighed : 



10.8230 grm. P gave 24.7925 PA- Ratio, 2.29072 

 7.7624 " 17.7915 " " 2.29201 



Hence P = 30.975. 



As these figures fall within the range of Schrotter's, they may be 

 averaged in with his series, the entire set of twelve determinations giving 

 a mean of 2.28955, ±.00032. 



Ter Gazarian'' determined the density of gaseous phosphine, from 

 which its molecular weight is deducible. For the weight of the normal 

 litre, in grammes, he found— 



1.52955 



1..52907 ^ 



1.52933 



1.52944 



1.52907 



1.52933 



Mean, 1.52930, ± .000054 



1 Compt. Rend., 100, 52. 1885. 

 -Joiirn. Chim. Phys., 7, 337. 3909. 



