﻿150 M. C. Marignac on the Specific Heats, Densities, 



This number agrees exactly with the determinations of M. Reg- 

 nault, who found 0*11294 between 13° and 58°. The atomic 

 heat is therefore equal to 9. 



For the specific heat of the mixture Br + CS 2 (51 per cent, of 

 bromine) I found 0*174, and consequently 27*1 for the molecular 

 heat. This is exactly the sum of the heats of the two liquids in 

 the mixture. 



Iodine: I+rcCS 2 . 

 n. c. p. C. C-18-lra. 



10 0219 887 194 13 



20 0-228 1647 376 14 



According to MM. Favre and Silbermann, the specific heat of 

 fused iodine is 0*1082; therefore its atomic heat is 13-7. 



Thus iodine is dissolved in sulphide of carbon without its spe- 

 cific heat being sensibly diminished. 



A solution with 10 molecules of sulphur, containing 14*3 per 

 cent, of iodine, is very near saturation. I could not operate on 

 more concentrated liquids. 



We see that all these solutions present a character very dif- 

 ferent from that observed in the aqueous solutions of acids and 

 salts. The diminution of specific heat resulting from solution, 

 or from dilution when this exists (as in the case of sulphur and 

 phosphorus), is always within narrow limits. Above all, the 

 molecular heat of these solutions never becomes inferior to that 

 of the solvent alone. 



General Observations. 



In the preliminary summary of his great work on the specific 

 heats of aqueous solutions, M. Thomsen announces that he can 

 deduce from his observations the general conclusion that^a dimi- 

 nution of specific heat always results from the mixture of water 

 with a solution. 



The generality which he attributes to this law is perhaps de- 

 pendent on the fact that all his researches were made upon com- 

 binations belonging to one class (hydrated salts, acids, and 

 bases). It is known, in fact, that a mixture of water and alcohol 

 has a specific heat superior to that of its elements. It results 

 from the facts reported in this memoir that solutions of sugar 

 have a specific heat equal to that of their elements. It may 

 even be remarked that among the few bodies for which M. 

 Thomsen has published the results of his experiments there is 

 one which behaves like sugar, viz. ammonia ; certainly the dif- 

 ferences do not reach the limits of error admitted by him as 

 possible. 



But, with this reserve, it is nevertheless true that this dimi- 

 nution of specific heat is very general, and that its proportion is 

 often very considerable. Thus we have seen that a solution of 



