486 M. R. Pictet on the Application of the Mechanical 



Liquid. 



Total 

 latent 

 heat. 



Water ! 536(cal.) 



Chloroform | 61 



Sulphide of carbon j 83*54 



Sulphuric ether | 8976 



Essential oil of turpentine 688 



Mercury 



Acetone 



Benzine 



Wood-spirit 



Chlorhydric ether 



Alcohol 



Sulphurous acid 



775 

 130 



9226 

 264 



921 

 210 



94-56 



Boiling- 

 point. 



Atomic 

 weight. 



External 

 latent 

 heat. 



Total heat 



by atomic 



weight. 



100 



9 



40(cal.) 



12 50 



60 



59 



531 



1080 



46 



38 



818 



1000 



35 



37 



815 



10-7 



155 



68 



614 



11-8 



350 



100 



606 



119 



55 



29 



11044 



11-45 



80 



39 



8-838 



1017 



67 



16 



20-48 



12-35 



10 



32 



8-58 



10-37 



78-2 



23 



14-9 



12 5 



-10 



32 



865 



112 



Internal 



by aton 



weigh 



11 8 

 10 0< 



9-7< 

 10 

 10-94 

 10-2 

 10-4 



9-9 

 113(1 



9-fr 

 115 

 104 



This Table shows, by the numbers contained in the last two 

 columns, that all the liquids have the same cohesion, and that 

 our hypothesis is true. These comparisons will perhaps make 

 it possible for us to calculate as a fraction of a millimetre the 

 real diameter of the atoms. Indeed cohesion plus the pressure 

 exerted upon the liquid are the only forces which resist the 

 disgregating action of heat ; and by varying the temperature 

 we get two numerical equations which would be perfectly de- 

 finite, if we knew the law of the attractions as functions of 

 the distances of the attracting particles, and the distribution 

 of the external pressure upon each atom. I reckon upon re- 

 suming this question in an early publication. 



The result of this numerical verification permits us to 

 establish another relation between the latent heats and the 

 atomic weights. 



Since cohesion is a constant quantity for all liquids, what do 

 the differences observed by M. Eegnault in the internal latent 

 heats at various temperatures represent ? They are only the ex- 

 pression of the work expended to separate the constituent atoms 

 of the liquid from the temperature t to tf. If we admit that 

 the temperatures are proportional to the amplitudes of the 

 flight of the atoms from each other, calling F the attraction 



F 



of two atoms for a distance corresponding to 1°, — = the at- 

 traction for a temperature x, and the integral of the work 

 necessary to raise the temperature from t to t' will be 



C v dx 

 f 1 ~— . This elementary work must be repeated for each atom 



Jt xm 



of the liquid ; and referring the work to the kilogramme we 



1 f * dx 

 shall have - 1 — ^ = work expended to raise the temperature 



