some Thermodynamical Relations. 



137 



values calculated directly from the vapour-pressure curves 

 generally agree very well with those recalculated from the 

 equation 



W=R + c(t'-t), 



as will he seen in the following table. With the exception of 

 chlorobenzene and bromobenzene, the comparison is only 

 made for those substances which have been investigated 

 through a large range of pressure, for otherwise it is impos- 

 sible to determine the value of e with sufficient certainty. 



1. Water and Carbon Bisulphide. Ratios of the products 



j- . t for CS 2 to those of water at the same pressures taken 



as abscissae, and the temperatures of water corresponding to 

 those pressures taken as ordinates. c= — 0*000399. 



Pres- 

 sures. 



Eeduced 

 ratios of 



^ . t, calc. 



dt 



from curves. 



Eeduced 

 ratios of 



4r • t, recalc. 

 dt 



from equa- 

 tion. 



Products 



f.* forCS,, 



calc. from 

 curves. 



f.*forCS 2 , 



recalc. from 



values for 



water and 



recalc. ratios. 



A 

 per cent. 



millim. 













50 



•804 



•8042 



675-7 



675-9 



+0-03 



100 



•796 



•7989 



1280-0 



1284-0 



+031 



150 



•794 



•7955 



1839 



1842 



+0-16 



200 



•787 



•7929 



2373 



2391 



+0-75 



300 



•787 



•7892 



3430 



3442 



4-0-35 



400 



•784 



•7864 



4436 



4451 



4-0-34 



500 



•784 



•7841 



5417 



5417 



00 



600 



•782 



•7822 



6361 



6364 



4-0-05 



700 



•780 



•7805 



7317 



7320 



4-0-04 



800 



•783 



•7790 



8235 



8197 



-0-46 



900 



•785 



•7777 



9281 



9196 



-0-92 



1000 



•780 



•7764 



10102 



10054 



-048 



1500 



■781 



•7715 



14507 



14325 



-1-27 



2000 



•767 



•7678 



18460 



18481 



4-0-11 



3000 



•750 



•7622 



26056 



26476 



4-1-59 



5000 



•755 



•7545 



41128 



41106 



-005 



There are only two cases in which the difference between 

 the calculated and recalculated values amounts to 1 per 

 cent., and these two cases occur close together and are in 

 opposite directions. Generally the differences are much 

 smaller than 1 per cent., while the differences between the 



ghestand lowest of the reduced values of ~ . t (calculated 



or recalculated) exceeds 6 per cent. 



2. Bromo- benzene and Chloro-benzene. The values for 

 these substances appeared to be identical. They were there- 

 fore fnken together and compared both with carbon bisulphide 



