A REVISION OF THE ATOMIC WEIGHT OF PHOSPHORUS. 1S5 



seem justifiable to reject the analyses of Samples R and 0. This conclusion is 

 supported by the fact that the water determinations failed to show a difference 

 between these samples. The results, however, indicate that the average ratio 

 1.34562 (77.300 per cent of silver) may be very slightly too low, owing to the 

 presence of disilver hydrogen phosphate. The ratio 1.34562, assuming the 

 atomic weight of silver to be 107.880, and assuming that silver bromide con- 

 tains 57.4453 per cent of silver, leads to an atomic weight of 31.043 for phos- 

 phorus, whereas the ratio 1.34564 derived from Samples N and P gives the value 

 31.037. The rounded-off value, 31.04, may be considered to be essentially free 

 from error from this source. 



SUMMARY. 



1. A careful study has been made of the conditions necessary for the prep- 

 aration of pure trisilver phosphate. 



2. It is found that silver phosphate can be almost completely dried without 

 fusion by heating in a current of dry air. 



3. The density of silver phosphate is found to be 6.37. 



4. It is found that silver phosphate does not adsorb a significant amount 

 of air. 



5. Nine analyses, made with four different samples, show that one gram of 

 silver phosphate yields 1.34562 gm. of silver bromide, whence the per cent of 

 silver in silver phosphate is 77.300. 



Therefore, 



If Ag = 107.88 P = 31.04 



If Ag = 107.87 P = 31.03 



