PBOFESSOB KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
79 
state of condensation in which they are contained in the compounds in question. In 
1841 *, reasoning from the results of Regnault’s experiments, he endeavoured to show 
that the atomic heat (that is the product of the atomic weight into the specific heat) 
of a compound is equal to the sum of the atomic heats for the states of condensation 
in which the elements are contained in the compound, and to ascertain what atomic heats 
are to be assigned to certain elements in certain compounds. On the assumption that 
the atomic heat of metals in compounds is as great as in the free state, he endeavoured 
to determine the atomic heat of oxygen, sulphur, &c. in certain compounds of these 
elements with the metals ; he came to the conclusion that an element (sulphur for. in- 
stance) may in some compounds have an atomic heat different from that which it has in 
the free state ; and the same element (sulphur or oxygen for instance) may have different 
atomic heats in different compounds; but the changes in the atomic heat of an 
element always ensue in simple ratios. I cannot here adduce the individual results 
which he obtained when he inferred the atomic heat of an element in a compound by 
subtracting from the atomic heat of the compound the atomic heat of the other 
elements in it, which he had calculated either from direct determinations of their 
specific heat, or from previous considerations. The essential part of Schroder’s con- 
ception is that in this manner the atomic heat of a body, as a constituent of a compound, 
may be indirectly determined ; and the result is that the atomic heat, at any rate of some 
elements in compounds, is different from what it is in the free state, and may be different 
in different compounds, and that the changes are in simple ratios. Schroder considered 
also that there was probably a connexion between these changes and those of the 
volumes of the elements, without, however, stating how from the one change the other 
might be deduced. 
11. L. Gmelin (in 1843) considered it as inadmissible, from the chemical point of view, 
to assign throughout such atomic weights to the elements as to make them agree with 
Dulong and Petit’s law. Certain exceptions must be admitted. Comparing the 
specific heats of oxygen, hydrogen, and nitrogen for the gaseous state with the specific 
heats of other elements in the solid state, he came to the conclusion that if the numbers 
given in § 2 as the equivalents ordinarily assumed be taken as atomic weights, the 
atomic heat of hydrogen, of nitrogen, and by far the greater number of the elements is 
equal to about 3-2 ; several of them twice as great, that of oxygen one-half, that of 
carbon (as diamond) one-fourth as great. With reference to the dependence of the 
atomic heats of the compounds on those of the elements, Gmelin expressed the opinion J 
that in general the elements on entering into compounds retain the atomic heats they 
have in the free state, but for individual elements, especially for oxygen and carbon, it 
must be assumed that their atomic heat changes in simple ratios with the compounds 
into which they enter. 
* Poggeitdoree’s ‘ Annalen,’ vol. lid. p. 269. f L. Gmelin’s ‘ Handbuch der Chemie,’ 4th ed. vol. i. p. 217. 
+ Ibid. p. 222 : compare an earlier remark of Gmelin which applies to this subject (1840) in the new edition 
of Gehler’s £ Physikalisches Wbrterbuch,’ vol. ix. p. 1941. 
MDCCCLXV. N 
