PAPERS ON CHEMISTRY AND PHYSICS 259 



Of this number about twenty appear to have been deter- 

 mined with the required degree of accuracy. The ex- 

 perimental slopes of each of these curves are given in 

 Table 1, together with the value of the factors obtained 

 by dividing the expeiiniental slope by the ideal slope. 

 970. Each factor was then located on the middle line, and 

 a straight edge was so placed across the chart that it 

 passed through this factor and the point chosen for 

 naphthalene. The point at which this line cuts the op- 

 posite side of the chart is the location of the substance in 

 question. Having located these substances they were 

 then used in finding the location of other substances, the 

 binary systems with naphthalene of which had not been 

 deteimined. 



In making the calculations involved in finding the lo- 

 cation of these other substances in the chart it was often 

 found that the positions of the substances already fixed 

 in the table could be checked repeatedly. In all cases 

 shown the positions finally adopted are the mean values 

 of several closely agreeing experiments using different 

 solutes or solvents. 



It will be observed that there may be some question, 

 especially where the factor has a value near to unity, as 

 to whether the factor should be slightly above or slightly 

 below the ideal position. In deciding this question one 

 may be guided somewhat by Hildebrand *s table of rela- 

 tive internal pressures and also by the solubility rela- 

 tions in other systems. 



In making the complete table we have calculated to 

 mole fractions the solubdity and freezing point measure- 

 ments of over 400 binary mixtures. Xot all of the sub- 

 stances studied appear in the chart. There have been a 

 large number of isolated systems investigated which 

 need only a few measurements in order to coordinate the 

 complete solubility relations of these substances. TVe 

 hope soon to make these measurements and to publish 

 the results in a later communication. 



rSES AND LEMTIATIONS OF THE CHART 



The uses of this chart are quite evident from the fore- 

 going discussion. In the first place it may be used to 



