THE ELECTROMOTIVE FORCE AND FREE ENERGY OF 
DILUTION OF LITHIUM CHLORIDE IN AQUEOUS 
AND ALCOHOLIC SOLUTIONS. 
J. N. PEARCE AND F. S. MORTIMER. 
Various experimental methods may be employed for compar- 
ing the activities of solutions of electrolytes, viz., freezing point, 
boiling point, vapor pressure, osmotic pressure, electrical con- 
ductivity and electromotive force. Of these, the latter is gen- 
erally more convenient of application ; it has the advantage in 
that measurements are more easily made and its use is not re- 
stricted to any particular temperature interval. In solutions 
ranging from the moderately dilute to the very concentrated 
it may be applied more accurately than the conductivity method. 
The electromotive force method, however, has its limitations. 
It shares with all of the other methods the disadvantage of be- 
ing inapplicable for solutions other than those, of the uni-univa- 
lent electrolytes. This, coupled with the troublesome factor of 
the boundary potential, has limited its usefulness. 
Many attempts have been made to eliminate this boundary 
potential. Some, following the lead of Ostwold , 1 have interposed 
solutions of an inert salt between the electrode vessels. Unfor- 
tunately, the electromotive forces thus measured vary consid- 
erably not only with the concentration of the interposed solution, 
but also with the nature of the electrolyte used. Consecpiently 
such measurements are of doubtful value. 
Nernst , 2 Planck , 3 Henderson , 4 Cumming , 5 and others have 
sought to overcome the effect due to boundary potential by in- 
troducing formulae involving the relative mobilities of the ions. 
A few cells have been set up which do not involve the trans- 
ference of ions from one electrode vessel to the other. Cells 
of this type are limited to those electrolytes for which it is pos- 
sible to find electrodes reversible to both of the ions in the so- 
lution. So far the only cells thus investigated from which cal- 
iMessungen, 3d ed., p. 448. 
theoretical Chemistry, Nernst, Translation of 6th German ed., p. 370. 
3 Wied. Ann., 40, 561, 1890. 
*Zeit. phys. Chem., 59, 118, 1907. 
5 Trans. Faraday Soc., 8, 86, 1912. 
