Theory of Heat to the Study of Volatile Liquids. 487 



)f the liquid from t to t' . Dividing this quantity by the 

 nechanical equivalent 433*5, we shall obtain the differences 

 )f the latent heats, and hence equation IX., 



— difference of the internal latent heats. . (IX.) 

 ioo'Ootj t x m v 7 



But Ave have demonstrated that cohesion is the same for all 



F 



liquids ; therefore the factor 



433 



_ r t 'dz = 

 •5 J, «* - ! 



K for all liquids, 



and equation IX. is simplified into, 



Difference of the internal heats =K« (X.) 



From this equation we conclude that, for two temperatures 

 and t' taken arbitrarily, the difference of the internal latent 

 heats , multiplied by the atomic weight, is a constant number for 

 all liquids. 



The following is a statement of some numerical verifications 

 with the differences of temperature 100° and 110°, 100° and 

 150 c 



*°, 50° and 150° 



1 



Liquid. 



Internal latent heats. 



Atomic 

 weight. 



Product. 



At 100°. 



At 110°. 



Difference. 





calories. 



496-29 



183-60 



5103 



39-64 



6733 



At 100°. 



496-29 



183-60 



5103 



39-64 



67-33 



At 50°. 



53612 



218-75 



56-75 



44-64 



7607 



calories. 



48836 



177-21 



49-86 



38-53 



65-34 



At 150°. 



456-70 



154 09 



4512 



33-76 



56-61 



At 150°. 



456-70 



15409 



4512 



33-76 



56-61 



calories. 

 793 

 6-39 

 1-17 

 111 

 1-99 



3959 



29-51 



5-91 



5-88 



10-72 



79-42 

 64-66 

 11-63 



10-88 

 19-46 



9 

 11 

 59 

 65 



38 



9 

 11 

 59 

 65 



38 



9 

 11 

 59 

 65 



38 



71-37 

 70-29 

 69-03 

 7215 

 75 62 



356-31 

 324-61 

 348-69 

 382-20 

 407-36 



714-70 

 81106 

 68617 

 707-20 



739-48 



Alcohol 



Chloroform 



Chloride of carbon . . . 

 Sulphide of carbon ... 







Chloride of carbon . . . 

 Sulphide of carbon . . . 



Water 





Chloride of carbon . . . 

 Sulphide of carbon . . . 



Of all experimental determinations, those of internal latent 

 heats are the most delicate in calorimetry ; so that we cannot 

 demand more complete accord between theory and experiment 

 within limits of temperature so wide apart ; the agreement is 

 sufficient to justify our law respecting the internal latent 

 heats. 



As a complement to the experimental synthesis of our 

 equations, we can apply them to a cycle similar to that of 



