74 
PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
tioned, that a dimorphous substance has the same specific heat in its two conditions. 
This he showed was the case with arragonite and calcite, and with iron pyrites and 
marcasite. But the most important is the discovery that in analogous compounds the 
products of the atomic weights into the specific heats are approximately equal. Neu- 
mann stated this last observation in the following manner : — “ In bodies of analogous 
chemical composition the specific heats are inversely as the stochiometrical quantities, 
or, what is the same, stochiometrical quantities of bodies of analogous chemical com- 
position have the same specific capacity for heat.” Neumann adduced 8 carbonates, 
4 sulphates, 4 sulphides (Me S), 5 oxides (Me O), and 3 oxides (Me 2 0 3 ), as showing 
this regularity, which is to be denoted as Neumann’s law *. 
5. Soon after the publication of Neumann’s researches in 1833, Avogadro published f 
a “ Memoir on the Specific Heat of Solid and Liquid Bodies.” He there gave a number 
of determinations of the specific heat of solid bodies made by the method of mixture. 
As far as can he ascertained by comparison with the most trustworthy of our newer de- 
terminations, these results are by no means so accurate as those of Neumann; but they 
are far more accurate than those which had been obtained up to about 1830, and many 
of them come very close to the best of our modern results. It would be unjust to 
Avogadro’s determinations $ to judge them all by one case, in which he obtained a 
totally erroneous result (for ice, by a modified method) ; and by the circumstance that in 
a subsequent memoir § he gives specific heats for several elements as deduced from his 
experiments, which are decidedly incorrect ||. Avogadro recognizes the validity of 
Hulong and Petit’s law. With reference to the specific heats of compound bodies, he 
considers that he had established, with tolerable probability, that for solid and liquid 
bodies the same regularity prevails which he had previously deduced for gases from 
Dulong’s experiments. That is, “ that the specific heat of the atom of a compound body 
is equal to the square root of the integral or fractional number expressing the atoms or 
parts of atoms which go to form the atom of the compound body such as it exists in the 
solid or liquid state, taking as unity the specific heat of the atom of a simple body in the 
samestate.” He observes that there is a difficulty incidental to the application of this 
law to solid and liquid bodies, which is not met with in the case of gaseous bodies, 
in which the composition by atoms or by volumes is held to be directly given by 
opportunity of seeing Neumann’s memoir cited by Pape, “ Commentatio de emendenda formula per quam calores 
corporum specifici ex experimentis metbodo mixtionis institutis computantur.” Regiomonti, 1834. 
* The objections of Regnault (Ann. de Chim. et de Phys. [3] vol. i. p. 131) as to the inadequacy of the 
proofs adduced 'by Neumann in support of the law do not apply. 
t Ann. de Chim. et de Phys. [2] vol. lv. p. 80, as an abstract from * Memorie della Societa Italiana delle 
Scienze residente in Modena,’ t. xx. Fascicolo 2 di fisica’. 
+ They are also found in Gmexin’s ‘ Handbuch der Chemie,’ 4 Auflage, vol. i. in the Tables, pp. 215-218 et seq. 
§ Ann. de Chim. et de Phys. [2] vol. lvii. p. 113. 
|| I only know Avogadro’s investigations from the abstracts published in the Ann. de Chim. et de Thys., and 
am not aware whether the hold corrections of Avogadro urged by Regnault ( Ann , de Chim. et de Phys. [2] 
vol. lxxiii. p. 10) were used in all his experiments, or only in some. 
