TO THEIR STATE OF IONIZATION—MACGREGOR, 243 
2, and J, will be characteristic of the ions and will not depend 
upon the salt from which they have been dissociated. A certain 
amount of evidence has been accumulated which may be said to 
point in this direction. In the case of several properties it has 
been shown that for solutions of considerable dilution, the 
ditference between the values of the property for solutions of 
two salts (ap and bp) having a common ion and the same 
molecular concentration, is independent of what the common 
ion may be; and the value of the difference divided by the 
number of gramme-equivalents per litre of the salts in solu- 
tion has been taken to be approximately the difference between 
the constants J, and l; Results of this kind have been 
obtained by Valscn and Bender for density and refracting 
power, by Kohlrausch for electrical conductivity, by Raoult for 
the depression of the freezing point, by Traube * for the change 
of volume on solution, by ROntgen and Schneider for compress- 
ibility, and by Jahn for the electromagnetic rotation of the 
plane of polarization. 
Applying the above expression, we have for the difference 
in the values of a property per unit of molecular concentration, 
(Pap—P op) /N=Kay Se) a hap thy) (4 a5— p+ lat ap — 4 bp (12 
and at infinite dilution 
ea Epp) = (np up Woo Batomuatcobos out0 (13) 
Had the experiments referred to been all carried out at extreme 
dilution, as were those of Kohlrausch, afterwards extended by 
Loeb and Nernst, the evidence would be quite satisfactory. 
Bat in general they have been made at only moderate dilution, 
and it is obvious from (12) that the approximate independence 
of the common ion on the part of (Pop Pap) /%, may be quite 
consistent with considerable variation in /,—1J,. It is clear that 
the first three terms of (12) may readily mask any variation 
in the last two, and that, if the last two did not vary, /,—J, 
could not in all cases be the same. 
* Ztschr. anorgan. Chemie, iii. (1892), p. 1. 
+ Ztschr. fiir phys. Chemie, ii. (1888) p. 948. 
