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Dr. Kopp on the Specific Heat of Solid Bodies. [May 12, 



Eg O3. It is seen that the compounds of those elements which, in the free 

 state, have themselves a smaller atomic heat than most other elements, are 

 characterized by a smaller atomic heat. 



This leads the author to discuss whether it is to be assumed that the 

 elements enter into compounds with the atomic heats which they have in 

 the free state. This assumption is only admissible provided it can be 

 proved that the atomic heat of a compound depends simply on its empirical 

 formula, and not on the chemical character or rational constitution. Much 

 of what has previously been said favours this view of the case. It is also 

 supported by the fact, which the author proves, that similar chemical cha- 

 racter in analogous compounds, and even isomorphism, do not presuppose 

 equality in the atomic heats, if in one compound an atomic group (a com- 

 pound radical) stands in the place of an elementary atom of another : for 

 instance, the atomic heat of cyanogen compounds is considerably greater 

 than those of the corresponding chlorine compounds, And those of ammo- 

 nium materially greater than those of the corresponding potassium com- 

 pounds. A further support for that assumption is found in the fact that, 

 regardless of the chemical character, the atomic heat of complex com- 

 pounds is found to be the sum of the atomic heats of simpler atomic groups, 

 the addition of which gives the formulae of those more complex compounds. 

 A few cases selected from the comparisons of the author may explain this. 



The atomic heats have been found, — 



For the oxides EO 11*1 



For binoxide of tin SnO^ 13-8 



Total for 24*9 



For sesquioxide of iron ^Fe^Og 26*8 



Or, 



For oxides 2EO = R.O^ 22*2 



For binoxide of tins Sn 03..= E3 O3 41-4 



Total for Eg 63 '6 



For arseniate of lead, , 'Bh^ ASgO^ 65-4 



Finally, the author shows, as supporting that assumption, that (as was 

 already maintained) water is contained in solid compounds with the atomic 

 heat of ice. The various determinations of the specific heat of ice give the 

 atomic heat of H2 O at 8*6 for temperatures distant from 0°, and at 9'1 to 

 9*8 at temperatures nearer 0°. The atomic heat has been found (to adduce 

 again a few comparisons) 



For crystallized chloride of calcium, ... €!a CI2 + 6H2 O 75*6 



For anhydrous chlorides R CI2 18"5 



Difference for GH^O 57l_g.g 



For crystalHzed gypsum €a S O^-f- 2H2 O 45*8 



For anhydrous sulphates ESO 26-1 



Difference for ...... 2 H2 O ]2ll=9'9 



2 



