670 Scientific Proceedings, Royal Dublin Society. 



For these two substances 



logu ^A - log.n F E = . 000900 . 



I A _ In 



therefore 



log lu [Pa (1 - M)/p B M] = 04198671 - 0101635m + 0-270739M 2 - 0179896m 3 . 



(Ill) 

 from which equation they calculated the ratios jp A /p B an d the molar percentages 

 of benzene in the vapour, benzene and toluene being regarded as substances of 

 normal molecular weight. 



The data obtained by Fortey and Young indicate that the vapour-pressures 

 of mixtures of benzene and toluene are represented without serious error by 

 the formula P = mP a + (1 - m)P Bj and in the table below the vapour- 

 pressures determined by Eosanoff, Bacon, and Sehulze are compared with 

 those calculated by them by the formula (II) and with those calculated by 

 the simple formula P = mP a + (1 - m)P b . 



The formula of Eosanoff, Bacon, and Sehulze obviously reproduces the 

 results better than the simple formula P = mP a + (1 - m)P e , but the devia- 

 tions in the latter case are by no means large. They are in the same direction 

 and of the same order of magnitude as those found by Fortey and Young from 

 their data. 



