PEOFESSOE KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 183 
knowledge, of the regularity, that compounds of analogous atomic constitution have 
approximately the same atomic heat. 
To this belongs, first, the existence of this regularity in the case of chemically 
similar bodies, which exhibit an analogy of atomic constitution, when their formulae 
are written with the atomic weights admitted in recent times for the elements, but 
which could not be recognized so long as the equivalents of the elements were taken as 
a basis, or the formula written, as by Regnault, with the use of the so-called thermal 
atomic weights. 
The approximate equality of the atomic heats of analogous nitrates and chlorates, of 
the alkalies for example, had been already observed. The same character, the haloid, 
is ascribed both to carbonates and to silicates, but as these formulae were formerly 
written, an analogy in the composition of chlorates and nitrates, or carbonates and 
silicates, could not be assumed. But salts of these four different classes, as well as 
arseniates and metaphosphates, have analogous atomic constitutions if we assume the 
recent atomic weights. The same salts have then also approximately equal atomic 
heats. We get the atomic heat 
Of chlorate of potass, K Cl 0 3 , § 88 M* 24*8 
„ the nitrates, RN0 3 , in § 88 M 23-0 
,, metaphosphate of soda, NaP0 3 , § 88 22T 
,, arseniate of potass, KAs0 3 , §88 25-3 
„ the carbonates, RG0 3 , § 86 M 207 
„ the silicates, RSi0 3 , § 86 M 20'5 
The differences in these approximately concordant atomic heats are partly essential 
and explainable. I come to this again (§ 95). 
According to the more recent assumptions for the atomic weights, certain perchlorates, 
permanganates, and sulphates have analogous atomic composition, and these salts have 
also approximately equal atomic heats ; this has been found to be 
For perchlorate of potass, KC10 4 , § 88 26 - 3 
„ permanganate of potass, K Mn 0 4 , §88 28 -3 
„ the sulphates, RS0 4 , named in § 88 . M 26T 
But approximate equality in the atomic heat is not only found in such compounds of 
analogous chemical composition as have similar chemical character, but also in such as 
have totally dissimilar chemical character. 
The chemical character of protosesquioxide of iron (magnetic iron ore) is quite different 
from that of neutral chromate of potass. Sesquioxide of iron, or arsenious acid, have a 
chemical character totally different from nitrates or arseniates, or bodies of similar con- 
stitution But for the first-named compounds and for the last-named compounds, as 
respectively compared with each other, there is analogy in chemical composition and 
approximate equality of atomic heat. The atomic heat has been found to be 
* M signifies the mean of all determinations. 
2 C 
MDCCCLXV. 
