PHOSPHORUS. 83 



Dumas* prepared pure phosphorus trichloride by the 

 action of dry chlorine upon red phosphorus. The portion 

 used in his experiments boiled between 76° and 78°. This 

 was titrated with a standard solution of silver in the usual 

 manner. Dumas publishes weights, from which I calculate 

 the figures given in the third column, representing the 

 quantity of trichloride proportional to 100 parts of silver : 



1.787 grni. PCI3 == 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 = 31.0314, ± .0467. 



Now, combining these two values, we have : 



By Schrotter P = 30.9562, d= .0074 



By Dumas " = 31.0314, dz .0467 



General mean " = 30.9580, =b .0073 



If = 16, this becomes 31.0292. 



The fact here noticeable, that Dumas' figures give a value 

 for P slightly higher than that deduced from those of 

 Schrotter, may be accounted for upon the supposition that 

 the phosphorus trichloride contained traces of oxychloride. 

 Such an impurity would tend to raise the apparent atomic 

 weight of phosphorus, and its occurrence is by no means 

 improbable. 



*Ann. Chem. Pharm., 113, 29. i860. 



