THE DISTRIBUTION OF MOLECULES 



83 



sures of other mixtures of such compounds, and thus check the theory by 

 corresponding experiments. 



The boihng points of many binary mixtures of alcohols, bromides, 

 iodides and acetates have been measured by Holley {Jour. Amer. Chem. 

 Soc, 24, 448 (1902)) and by Holley and Weaver {Jour. Amer. Chem. 

 Soc., 2/, 1049 (1905))- For mixtures containing 0.5 mol fraction of each 

 component the total vapor pressure of the mixture was compared with 

 that of the separate pure components and then by a series of trials the 

 partial pressure and q) were calculated by Equations (25). 



TABLE III 



Observed and Calculated Mixture Energies (p for Binary 

 Mixtures of Alkyl Bromides and Alcohols 



Table III gives a summary of the values qposs which were thus obtained 

 from the experimental data on mixtures of bromides with alcohols. The 

 values marked qpcoz have been calculated ^ by Eq. (17) from the following 

 values of y. 



Hydrocarbon-bromine 7(1^"^^) == 10. ergs per cm.- 



Hydrocarbon-hydroxyl yC^-OH) = 33.7 

 Bromine-hydroxyl Y(Br-OH) = 49.6 



The value of Y(R-Br) was assumed to be 10 as a reasonable interpola- 

 tion between y(R-I) = i3-7 and y(R-C1) =4.1 as given in Table H. 

 The values of y(R-OH) and Y(Br-OH) were then determined by least 

 squares to make the agreement as good as possibfe between ^>ohs and ^>cai 

 in Table HI. 



Considering the rather rough nature of these data and the uncertainty 

 in some cases as to whether the normal or iso-compounds were used, the 

 agreement is as good as could be expected. The signs of the differences 

 between qpobs and (^cai seem to be distributed nearly at random. 



^ The surfaces 5 of the molecules were calculated from the molecular weights and 

 the densities at room temperature, assuming arbitrarily close packed spheres. The 

 surface fractions a, b, c and d were calculated by taking for the surface of the bromine 

 atom 25. A^ and for the hydroxyl group 30.A^. 



