Reilly & HiCKiNBO'j'TOM — Concentration of Alcoholic Liquors. 243 



The values of K obtained experimentally by Sorel varied from 7'15 at 

 5 per cent, concentration to 9'9 at 1 per cent, concentration. The calculated 

 values of /^ agree approximately with those obtained directly (see Table IV), 

 thus confirming the relation between the two coefficients we have already 

 deduced. 



It will be seen that the distillation coefficients of the alcohols increase in 

 an approximately regular manner with an increase in the molecular weight. 

 The occurrence of a branched chain in the compound results in an increased 

 volatility, as shown by a comparison of the distillation results of the butyl 

 alcohols. The trend of the figures is analogous to that in the case of the 

 lower fatty acids. The fact that the solute of lower boiling point exerts a 

 greater pressure in solution than one of higher boiling point is probably 

 dependent on the fact that the attraction of the unlike molecules (alcohol 

 for water) diminishes with rise of molecular weight of the alcohols, as shown 

 by decreasing miscibility. 



In connection with these comparisons it should be mentioned that there 

 is often an evolution of heat and a volume change on mixing the alcohols 

 with water. This is true, however, with large excess of water ; but, for 

 example, with sixty molecules of alcohol to forty of water there is an 

 absorption of heat in the case of tertiary butyl, H-propyl, and ■iso-butyl 

 alcohols. The contractions on mixing also diminish with rise of weight of 

 alcohol (Young and Eortey).i 



Table IV. 



It is seen from Table IV that the distillation coefficient is influenced by 

 the concentration. This is not due to temperature eiiects, since it has been 

 found that on calculating the value of K, it only diminishes slightly with 

 increasing temperature, as in Table V. 



1 Trans. Chem. Soo., 1902, 81, 717- 



