The Effect of Pressure on the Electrical Conductance of Salt Solutions in Water

Abstract

New data are presented for the change with pressure of the equivalent conductance of the following $\frac{1}{100}$ normal salt solutions in water: at 30\ifmmode^\circ\else\textdegree\fi{}C, HCl, LiCl, NaCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, ${\mathrm{Na}}_{2}$S${\mathrm{O}}_{4}$, Na${\mathrm{C}}_{2}$${\mathrm{H}}_{3}$${\mathrm{O}}_{2}$, Ca${\mathrm{Cl}}_{2}$, Ba${\mathrm{Cl}}_{2}$, Th${\mathrm{Cl}}_{4}$, ${\mathrm{K}}_{3}$Fe(C${\mathrm{N})}_{6}$, ${\mathrm{K}}_{4}$Fe(C${\mathrm{N})}_{6}$; and at 75\ifmmode^\circ\else\textdegree\fi{}C, all the above solutions excepting NaF and Th${\mathrm{Cl}}_{4}$. The pressure range at 30\ifmmode^\circ\else\textdegree\fi{}C is 1-10,000 kg/${\mathrm{cm}}^{2}$, and at 75\ifmmode^\circ\else\textdegree\fi{}C it is 1-11,000 kg/${\mathrm{cm}}^{2}$. It is pointed out that the observed maxima in the equivalent conductance can not be entirely caused by a change in the degree of dissociation of the ions with pressure. By using a well-known expression for the equivalent conductance at infinite dilution, and also by using the Debye-H\"ucklel formula, it is shown in each case that there must be a large change in the diameters of the ions due to the pressure if the theory is to agree with the data.