314 BULLETIN OF THE UNIVERSITY OF WISCONSIN. 



Tables 3 to 11 do not contain all the salts represented in 

 Table 1. The freezing-points of barium chloride solutions have 

 lately been determined by Jones and Chambers 1 between ap- 

 proximately the concentrations 0.1 and 0.6 normal, as have also 

 those of chlorides and bromides of other alkaline earths. Table 

 3, giving the results obtained with NaCl, indicates that for the 

 concentrations investigated (0.2 to 1.0 normal approximately) 

 the molecular weight is practically constant. For about 0.2 

 normal the molecular weight was found to be 32.6, which cor- 

 responds to a dissociation of 79.4 per cent. ; for an approxi- 

 mately normal solution the molecular weight. was found to be 

 31.7, which corresponds to a dissociation of 84 per cent. These 

 two results represent the extreme variations of the values in 

 Table 3. For the average value of the six determinations, 32.2, 

 the dissociation is 81 per cent. According to Table 1 the de- 

 gree of dissociation (calculated according to the usual formula 



— - ) is about 79 per cent, for the 0.2 normal solution and 



Aoo 



70 per cent, for the normal solution. 2 The degrees of disso- 

 ciation 79 per cent, and 70 per cent, correspond respectively 

 to the molecular weights 32.7 and 34.4. It is clear then, 

 that the degree of dissociation for the most dilute solution tested 

 is found to be the same by freezing-point and conductivity 

 methods to within the experimental error of the former method. 

 But the dissociation increases rapidly with the dilution accord- 

 ing to the conductivity, whereas the freezing-point results show 

 that it at least remains constant, if it does not diminish with the 

 increase of the dilution within the limits tested. C. Dieterici 3 

 has shown by his very careful measurements of the diminution 

 of the vapor tension of NaCl solutions at 0° that between the 

 limits 0.1 and 1.0 normal the molecular diminution of the 

 vapor tension decreases as the dilution increases. E. W. Wood 4 



'Amer. Chem. Jour. 23, 89 (1900). 



*In calculating the degrees of dissociation from the conductivity the values 

 of the conductivity at infinite dilution were taken either directly from the high- 

 est values given in the table of conduct! vites; or when the trend of the curve 

 (which was in all cases charted) required it, from the careful extrapolation of 

 the curve. 



8 Wied. Ann. 62, 616 (1897). 



«Zeit. phys. Chem. 18, 522 (1895). 



