124 SPECIFIC HEAT OF ATOMS. 



cobalt appears to be once and a half, and that of the atom of 

 carbon to be one-half of that of lead. But b'ismuth appears to 

 have no clear relation to the others, the capacity of its atom 

 being 0.6736, referred to that of lead as 1. The general results, 

 therefore, may be stated as follows : 



Specific heat of atom of lead . . 1 

 tin . 1 



zinc . . 1 



copper . 



nickel . . 1 



iron . . I 



,, platinum . . 1 



sulphur . . 1 



,, mercury . . 1 



5, tellurium . 2 



arsenic . . 2 



silver . . 2 



gold . . 2 



,, phosphorus . 4 



iodine . . 4 



cobalt . .li 



carbon . . % 



Messrs. Dulong and Petit, whose researches supplied these 

 valuable results, drew a more general conclusion from them, 

 namely that all atoms, or at least all simple atoms, have the 

 same capacity for heat, and that those atomic weights which 

 are inconsistent with that supposition, ought to be altered and 

 accommodated to it. The specific heat of a body would thus 

 afford the means of fixing its atomic weight. Some of the al- 

 terations in the atomic weights, which would follow the adop- 

 tion of this law, might be advocated upon other grounds, such 

 as halving the atomic weights of silver and gold, but certain 

 other changes equally inevitable are wholly inadmissible ; such 

 as dividing the atom of tellurium by two, or reducing it from 

 802 to 401, although the most perfect analogy subsists between 

 tellurium and sulphur in their compounds, in all of which 802 

 parts tellurium, and not 401, replace 201 sulphur or one equi- 

 valent. The equivalent of phosphorus would require to be 

 divided by four, while that of arsenic, which it so closely re- 

 presents in compounds, is divided only by two. Of the ad- 

 mitted equivalents of nickel and cobalt also, which replace each 



