188 
PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
The Tables in § 84 to 89 contain data for several such comparisons, which lead to 
the same result as the preceding — that the atomic heat of water contained in solid com- 
pounds may, by subtracting the atomic heat of the anhydrous solid from that of the 
hydrated solid compound, be obtained in sufficient approximation to the atomic heat 
deduced from the direct determination of the specific heat of ice. The deviations from 
each other and from the atomic heat of ice as directly determined, which these indirect 
determinations exhibit, are not to be wondered at when it is considered that all uncer- 
tainties in the atomic heats, from whose difference the atomic heat of solid water is 
deduced, are concentrated upon this difference. 
98. The view already expressed and defended (compare especially § 12 and 13), that 
atoms and atomic groups are contained in solid compounds with the same atomic heat 
which they have in the free state, is opposed to the view which has also been frequently 
expressed and defended — that the atomic heat of an element may in certain com- 
pounds differ from what it is in the free state, and may be different in different com- 
pounds. This view, and the reasons which may possibly be urged in its favour, must 
here be discussed. 
The first statement of this view (compare § 6) simply goes to assert that the atomic 
heats of compounds may be calculated in accordance with the values resulting from the 
determinations of the specific heat, assuming that one constituent of the compound has 
the same atomic heat as in the free state, the other an altered one. What alteration is 
to be assumed depends merely on what assumption adequately satisfies the observed 
specific heat of the compound. The accuracy of the assumption is susceptible of no 
further control ; the assumption itself cannot be regarded as an explanation of the 
observed atomic heat of the compound. And nothing is altered in this by assuming 
(compare § 6 and 11) that the changes in the atomic heat of a substance on entering 
into chemical compounds take place in more or less simple ratios. 
A greater degree of probability must be granted to the view (compare § 10) that the 
atomic heats of the constituents of compounds, and the differences in the atomic heats 
of these bodies, according as they are combined or in the free state, depend upon the 
state of condensation in which these bodies are contained. If, for instance, from a 
consideration of the specific gravities or specific volumes (the quotient of the specific 
weights into the atomic weights) of compounds and of their constitutents, a conclusion 
could be drawn with some degree of certainty as to the state of condensation in which 
the latter are present in the former, and if definite rules could be given for the varia- 
tions of the atomic heats with the state of condensation, the result of such an investiga- 
tion, if it agreed with the observed results for the atomic heats of compounds, might be 
called an explanation of these observations. But what is here presupposed is partially 
not attained and partially not attempted. And, moreover, as far as can be judged 
from individual cases, the same element, when contained in different states of condensa- 
tion, appears to have the same atomic heat. It has been attempted to deduce the state 
of condensation, or the specific volume of oxygen in its compounds with heavy metals, 
