178 
PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
for the specific heat of the same body at the same temperature. At temperatures at 
which a body softens, the specific heat does indeed vary considerably with the tempera- 
ture (compare for example § 77); but these numbers, as containing already part of the 
latent heat of fusion, give no accurate expression for the specific heat, and are altogether 
useless for recognizing the relations between this property and the atomic weight or 
composition. 
Just as little need the small differences be considered which Regnault found for a 
few metallic substances according as they were hammered or annealed, hard or soft. 
For dimorphous varieties of the same substance, even where there are considerable 
differences in the specific gravity, the specific heats have not been found to be materially 
different (compare FeS 2 , § 83 ; T-i© 2 , § 85; Ca€ 0 3 , § 86). The results obtained with these 
substances appear to me more trustworthy than those with graphite and the various 
modifications of boron and silicium, which moreover have given partly the same specific 
heat for the graphitoidal and adamantine modification of the same element. What 
trustworthy observations we now possess decidedly favour the view that the dimorphic 
varieties of the same substance have essentially the same specific heat. 
91. The view has been expressed that the same substance might have an essentially 
different specific heat, in the amorphous and crystalline conditions. I believe that 
the differences of specific heat found for these different conditions depend, to by far 
the greatest extent, upon other circumstances. 
The Tables in § 83 to § 89 contain a tolerable number of substances which have been 
investigated both after being melted, and also crystallized ; there are no such differences 
in the numbers as to lead to the supposition that the amorphous solidified substance 
had a different specific heat to what it had in the crystallized state. No such influence 
of the condition has been with any certainty shown to affect the validity of Dulong 
and Petit’s, or of Neumann’s law. I may here again neglect what the determinations of 
carbon, boron, or silicium appear to say for or against the assumption of a considerable 
influence of the amorphous or crystalline condition on the specific heat. Re gn AULT 
found (§ 85) that the specific heat of artificially prepared (uncrystalline'?) and crystal- 
lized titanic acid did not differ. According to my investigations (§ 48) silicic acid has 
almost the same specific heat in the crystallized and in the amorphous condition. 
In individual cases, where the specific heat of the same substance for the amorphous 
and crystallized modification has been found to be materially different*, it may be shown 
that foreign influences affected the determination for the one condition. Such influ- 
ences are especially: 1. That one modification absorbed heat of softening at the tem- 
perature of the experiment ; that is doubtless the reason why the specific heat of yellow 
* De la Rive and Makcet (Ann. de Chim. et de Phys. [2] vol. lxxv. p. 118) found the specific heat of 
vitreous to be different from that of opaque arsenious acid, and considered the fact to he essential ; hut their 
method was not fitted to establish such a difference. Pape’s view, too (Poggendokff’s Annalen, vol. cxx. 
pp. 341 and 342), that it is of essential importance for the specific heat of hydrated sulphates whether the salts 
are crystallized or not, does not appear to me to he proved by what he has adduced. 
