50 



THE ATOMIC WEIGHTS. 



the usual method, as follows, in order to obtain the most 

 probable value : 



From specific gravity of N N = 14.0244, ± 



" ammonium chloride " =^ 14.0336, d= 



" ratio number four " = 14.0330, ± 



" silver nitrate " = 13.9840, ± 



" potassium nitrate " =13.9774,1+; 



" sodium nitrate " = 13.9906, ± 



General mean. 



14.0210, zfc .0035 



0039 



0153 

 0150 

 0174 

 0216 

 0163 



If oxygen is 16, this becomes 14.0291. Stas found N = 

 14.044. The difference is .015, showing a remarkably close 

 agreement. 



CARBON. 



Although there is a large mass of material relating to the 

 atomic weight of carbon, much of it may be summarily set 

 aside as having no value for present purposes. The density 

 of carbon dioxide, which has been scrupulously determined 

 by many investigators,* leads to no safe estimate of the con- 

 stant under consideration. The numerous analyses of hydro- 

 carbons, like the analyses of naphthalene by Mitscherlich, 

 Woskrescnsky, Fownes, and Dumas, give results scarcely 

 more satisfactory. In short, all the work done upon the 

 atomic weight of carbon before the year 1840 may be safely 

 rejected as unsuited to the present requirements of exact 

 science. As for methods of estimation we need consider but 

 three, as follows : 



First. — The analysis of organic salts of silver. 



Second. — The determination of the weight of carbon dioxide 

 formed by the combustion of a known weight of carbon. 



* Notably by Lavoisier, Biot and Arago, De Saussure, Dulong and Berzelius, 

 Buff. Von Wrede, Regnault, and Marchand. For details. Van Geuns' monograph 

 may be consulted. 



