48 Prof. R. A. Lehfeldt on the 



bable error of log p 50 = 0*0005, whence p 50 = 175*3 + 0*1. This 

 reduced to 0°and sea-level in lat. 45° becomes /> 50 = 174" 8 mm. 

 The results are shown in the accompanying diagram (fig. 2) and 



Fiff. 2. 



90 



100 



40 50 60 70 80 



Molecular per cent, of alcohol (or carbon tetrachloride). 



in the tables below. I have only been able to find one earlier 

 observation on the same mixtures : from Regnault's experi- 

 ments * on mixtures of alcohol and benzene at higher and 

 lower temperatures one finds by interpolation p 50 = 39l mm. 

 for a mixture in equal volumes of the liquids, whilst the value 

 from my curve is 393 mm. It is satisfactory to find this 

 confirmation, slight as it is, because the alcohol mixtures are 

 the least certain, on account of the inevitable presence of 

 traces of water. 



The difference between the alcohol curves and those of the 

 normal liquids is most marked; for while mixtures of carbon 

 tetrachloride and benzene, or carbon tetrachloride and toluene, 

 have a vapour -pressure never very different to that which 

 would be obtained by interpolation from the pressures of the 

 * Kegnault, Mem, de V Acad, xxvi. 



