Thrs lcttcr prcwnts the first collection of consIstcnt n~~~~uren~~nt~ of Hall constants for ddute solutions of clectrolytes-25 aads, salts, bases c_omposcd 01 6 nnions and 6 cations. Thcsc rcsuh are mtcrprctcd In terms of smiplc models tor the ionic solvatlon.
The Hall effect has been for long a choice tool for the study 0: the solid state, cspecrally of scmi-conductors where it enabies one to determine the conccntration of the charge carriers. Thrs effect should be, in the same way, of great help in the study of transport phenomena in ionic solutions. It is only the great difficulties of its application to the liquid state which explain the present lack of experiments in this field.
WC used the ac cross-modulation method [I] to make Hall measurements m electrolytes at room tcmpcrature. The electric and magnetic fields were applied at 243 Hz and 75 Hz respectively, and the 168 HL Ifall voltage difference frequency was measured. Rms values for I and B were 500 PA and 0.2 T respectively.
A pure silica parallelcpiped-shaped cell with platinum electrodes was used, the electrolyte specimen dimcnsions being: thickness: 0.200 mm; width: 8 mm; length: 3.5 cm.
In the most favourablc case the Hall voltdgc is as :ow as 250 nV. With an applied current electrode tcnsion of 250 V (i.e. IO9 times the Iiall tension), a nonalignment tension arrses whrch is IO6 times the llall tension.
As for induced tension, it extends to a few hundreds of mV or more if no precaution is taken; it must be reduced to a few tens of PV. To get simultaneously a very weak induced tension both in the current and measuring circuits, WC used a differential mode device, the cell and connections being as symmetrical as pos-