742 Dr. S. "R. Milaer on the Eject of lnterionic 



different range for the two different branches, then also the 

 radium series can be deduced from the uranium series. Of 

 course, such a deduction is very hypothetical. 



Recently von Hevesy *, and also Fajans f, proved that a 

 relation exists between the expulsion of a and f$ rays and the 

 change in chemical properties. As the atomic weight of 

 the products also depends on the number of a. particles 

 expelled and finally "a relation of a similar though not 

 nearly so definite a character as that found by Geiger for 

 the a rays appears to hold between the velocity of expulsion 

 of ft particles and the period of transformation of the product 

 concerned "•$-, it seems not improbable that all radioactive 

 constants depend on the number of charges expelled only. 



Summary. 



The following relations seem to exist, first, between the 

 initial velocity of the a rays and the number of charges 

 expelled during disintegration: log V a =A + wB, and second, 

 between the period of transformation and the number of 

 charges expelled: log\ = C + ?iD, where B and D are general 

 constants, A and C special constants for each series, and n the 

 number of charges expelled. 



Noordwvk-Zee, Duinhoeve, 

 February 1913. 



LXXIX. The Effect of lnterionic Forces on the Osmotic Pres- 

 sure of Electrolytes. By S. R. MlLNEK, JD.Sc, Lecturer in 

 Physics, The University of Sheffield § . 



THE osmotic pressure of dilute solutions of inorganic 

 electrolytes, as determined from the lowering of the 

 freezing-point, is always nearly, but not quite, as great as it 

 would be if the dissociation of the electrolyte were complete. 

 The explanation given by Arrhenius in 1887 that in such 

 electrolytes an appreciable fraction of the molecules remains 

 undissociated, is still the one which is generally accepted. 

 This theory is strongly supported by the agreement of the 

 values of the dissociation calculated from freezing-point and 

 from conductivity measurements, but it gives results for its 

 variation with the concentration which are, as is well known, 

 wholly at variance with the law of mass-action; and although 

 many attempts have been made to explain this discrepancy 



* Phys. Zeitsch. xiv. p. 50 (1913). 

 t Phys: Zeitsch. xiv. p. 137 (1913). 

 % Loc. cit. p. 610. 

 § Communicated by the Author. 



