M. CLAPEYRON ON THE MOTIVE POWER OF HEAT. 



371 



From the experiments made by several philosophers we are enabled to 



calculate the values corresponding to the boiling point of k and -£-, for 



dt 

 different liquids; we can therefore deduce from them the corresponding 



values of — 

 C 



0< C c! C.^ -g 



NAMES 



of 



Liquids. 





Sulphuric Ether., 

 Alcohol 



Water 



Essence of Tur- 

 pentine 



1 

 28-12 



1 

 25-19 



1 

 29-1 



1 



30 



-^5 = 



.^ !!■?.. 



2-280 

 1-258 

 0-451 

 3-207 



CS g Oh 



90-8 

 207-7 

 54-3-0 



76-8 



Tempera- 

 ture 

 of 

 ebullition. 



Corre- 

 sponding 

 values 

 1 



of 77- 



35-5 

 78-8 

 100- 

 156-8 



1-365 

 1-208 

 1-115 

 1-076 



These results confirm, in a striking manner, the theory that we are 

 explaining ; they show that C is slowly augmented with the tempera- 

 ture, as has been already stated : we have seen that for < = o, — - = 1-41 



whence C = 0*7092 ; this result is deduced from experiments upon the 

 velocity of sound. 



We here find, starting from experiments upon the vapour of water 



for t - 100°, -i- = 1-115, whence C = 0-S9G9 ; C is therefore in- 

 creased from at 100° to 0-187, which gives as the mean of the dif- 

 ferential coefficient between tliese two limits 



dC 

 dt 



= 0-00187. 



The mean of the two experiments perfonned by MM. De Laroche 

 and Berard gives us, between the limits 22°-83 and 96-90, for the mean 



value of — the quantity 0-002565. 



These two results differ little from each other, and their divergence 

 will be sufficiently explained, by reflecting on the number and the va- 

 riety of the experiments whence the data on which they are founded 

 are derived. 



