62 PHYSICS: E. H. HALL Proc. N. A. S. 
character from H and OH, no such simple behavior is to be expected, nor 
is it found Rules for such systems have still to be discovered. 
The reason for the above dependence of solubility upon compound 
formation becomes evident when we examine the freezing-point depression 
curve of a system such as LiiSO^-H^SO^ The absolute freezing-point 
of the salt is so high that , unless compound formation took place, solu- 
bility in the acid at ordinary temperatures would, according to the 
Schroder-Le Chatelier equation, 4 necessarily be negligible. The removal 
of simple solute molecules by combination with solvent, however, results 
in an increased solubility, and the extent of such increase depends, natu- 
rally, upon the extent of compound formation. The further develop- 
ment of this topic and the presentation of quantitative results will be 
given in forthcoming articles in the Journal of the American Chemical 
Society. 
* Contribution No. 350. 
1 Kendall and Booge, /. Amer. Chem. Soc, 39, 1917 (2323). 
2 Carpenter, Ph.D. Dissertation, Chicago, 1915; Gibbons, /. Amer. Chem. Soc, 37, 
1915 (149); Booge, Ph.D. Dissertation, Columbia, 1916; Gross, Ph.D. Dissertation, 
Columbia, 1919; Landon, Ph.D. Dissertation, Columbia, 1920; Adler, Ph.D. Dissertation, 
Columbia, 1920; Davidson, Ph.D. Dissertation, Columbia, 1920. 
3 Kendall and Booge, loc. cit.; Gross, loc. cit. 
4 Roozeboom, Heterogene Gleichgewichte, 2, 1904 (270-84). 
THE PELTER EFFECT 
By Edwin H. Hall 
Jefferson Physical Laboratory, Harvard University 
Read before the Academy, November 16, 1920 
When a current of electricity goes from metal a, in which the free- 
electron fraction of the conductivity is (kf -r- k) a , to the metal in which 
the corresponding fraction is (kf -f- k)p, ionization or reassociation must 
take place at the junction, according as (kf -f- k)p is greater or less than 
(kf -7- k) a . The resulting change of condition is the same whether we 
assume the ionization or reassociation to take place after or before the 
crossing of the interface between a and /3. We shall use each of these 
hypotheses in turn, beginning with the first. 
The gain of energy, and so the heat energy absorbed, by the unit quan- 
tity of electricity, 10 coulombs, in the form of electrons, in crossing the 
boundary from a to /3 is 
n - (*').('•• - 4 + (f ).("' - '•-). + ( p ' - p -) 
where (Pp — P a ) f means the P f of /3 minus the P of a, etc., the nomencla- 
ture according in general with that of my preceding papers. 
