THE NEW THEORY OF SOLUTIONS. 417 



Influence of concentration. — If AT were strictly propor- 

 tional to g the values of M'AT/g in any vertical column 

 would be the same. For the alcoholic solutions this is 

 practically the case, even up to a concentration of over 1 7 

 per cent, for the solutions of salicylic acid. In general, 

 however, as is illustrated by the solutions in benzene, AT 

 does not increase as rapidly as the concentration, hence the 

 molecular rise diminishes as the concentration increases. 

 For a few solutions like those of camphor and naphthalene 

 in chloroform the reverse state of things is exhibited, the 

 molecular rise increasing as the concentration increases. 

 These results support the conclusion already stated regard- 

 ing the validity of Wiillner's law as applied to dilute 

 solutions. 



hifluence of the chemical nature of the dissolved sub- 

 stance. — Since the values of the molecular rise, for the same 

 dissolved substance, vary to some extent with the concen- 

 tration, in order to most satisfactorily compare the values 

 given by different dissolved substances, the effect of change 

 of concentration must be allowed for. This is usually done 

 by finding the probable value of M'/\T/g for an extremely 

 dilute solution, for according as the solution is more dilute 

 the more closely it may be expected to conform to the ideal 

 laws. A convenient method consists in plotting a curve 

 with the observed values of M'AT/g as ordinates and either 

 the values of AT or g as abcissae. On extrapolating and 

 finding the ordinate corresponding with AT or g = o the 

 probable value is obtained for the molecular rise in an 

 extremely dilute solution. The numbers given at the top of 

 each of the columns headed M'AT/g in the preceding tables 

 are the values thus deduced.^ With benzene as solvent, 

 although the molecular weights of the two dissolved sub- 

 stances differ considerably and the variation in AT/g is com- 

 paratively speaking large, these values for the molecular 

 rise, viz., 26*2 and 26*9, closely agree. The values given 

 by the two alcoholic solutions, viz., 11*3 and 1 1 '5, are 

 also in satisfactory agreement. Unless in the case of a 

 particular class of substances dissolved in certain solvents — 

 associated solutions— to be discussed at a later stage, the 



