﻿and Expansions of some Liquids, 147 



always less than that of the water by itself which they contain. 

 This is true even of the most concentrated solution I have ex- 

 amined, which contained 24*5 for 100 of acid. There is thus 

 always a diminution of specific heat by the mixture of the water 

 with these solutions. 



Hydrochloric acid is one of the bodies for which the results 

 obtained by M. Thomsen have been already published. Here 

 is the comparison of the molecular heats found by that savant 

 with those indicated by the formula deduced from my experi- 

 ments : — 



n. Thomsen. Calculated. 



10 162 162-9 



20 338-5 338 



50 872 874 

 100 1769 1773 

 200 3557 3572 



The differences little exceed the errors possible on the one side 

 and the other, except for the solution with 200 molecules of 

 water. 



The result obtained by M. Thomsen for this solution appears 

 to me very low : it would suppose a singular anomaly in the law 

 of the progression of the differences C — 18rc. 



Chloride of Sodium : NaCl + n Aq. 



C 



». c. p. Observed. Calculated. C — 18%. 



12-5 08100 283-5 2296 2296 + 4-6 



25 0-8760 508-5 4455 445-5 - 4-5 



50 0-9280 958-5 889-5 888-3 —117 



100 0-9596 1858-5 1783 1784 -16 



200 0-9782 3658-5 3578 3582 -18 



The molecular heat is expressed by the formula 



n 1Q Ql\AK . 481 2100 



C = 18n— 20-45+ 5— 



n n z 



Inspection of the last column shows that the dilution of a so- 

 lution of chloride of sodium always occasions a diminution of the 

 molecular specific heat. A solution containing about 18 mole- 

 cules of water to 1 of the salt has the same specific heat as the 

 water which it contains ; but the specific heat of more dilute so- 

 lutions is less than that of the water contained in them. 



Solutions of chloride of sodium have also been studied by M. 

 Schiiller. From his experiments their specific heat may be ex- 

 pressed by the formula 



100 +p 



L2 



