Vaporization of Liquids. 299 



not hold above 40°. To obtain more reliable values at higher 

 temperatures, I have calculated the latent heats of benzene by 

 means of Clausius's equation, 



by which the latent heat may be obtained up to the critical 

 point. By this means one may calculate the latent heats at 

 different temperatures of some other substances for which they 

 have not been experimentally measured, but in which v, v ; , and 

 p are known, and so obtain a fair number of cases by which to 

 test the validity of (9). The data have been obtained almost 

 completely from papers by Bam say and Young, or Young 

 and Thomas, in the Philosophical Magazine, Philosophical 

 Transactions, and Journal of the Chemical Society. 

 dp 



The values of -f and 



Oil 



of L have been given in one or two 

 cases by the observers, being obtained from an empirical 



has 



equation for the 



vapour-pressure. In the other cases -~ 



been determined by tabulating the differences in log 10 p for 

 20° (the curve for logp being nearly a straight line, these 

 differences do not differ greatly from the differential coeffi- 



-j- from them by the relation 



20 " 0-4343' 



a method which gives dp/dt somewhat more accurately than 

 taking differences on the vapour-pressure curve itself. The 

 values of the latent heats have generally been smoothed by a 

 curve before using in the equation for b. 



Below are given the values of b and a for a number of 

 substances, with L; determined in this way. 



Benzene. 



cients), and calculating 



dt p 



t. 



v. 



v'. 



I* 



b. 



a. 



02 



1-1113 



8141 



1010 



0-8900 





173 



1-1341 



3523 



98-7 



•8962 



1-671 XlO 9 



32-0 



1-1544 



1874 



95-9 



•8970 



1-682 



48-4 



1-1784 



1001 



92-9 



•8975 



1-690 



67 



1-2070 



538-0 



890 



•8910 



1-683 



110-4 



1-2812 



164-2 



80-1 



•8820 



1-675 



1634 



1-4008 



53-93 



68-3 



•8600 



1-673 



181-4 



1-4523 



38-84 



640 



•8512 



1-677 



202-3 



1-5225 



26-97 



59-0 



•8490 



1-707 



