Cell, Standard Voltaic, Latimer Clark's.
A mercury and zinc electrode couple with mercurous sulphate as excitant
and depolarizer. The positive element is an amalgam of zinc, the
negative is pure mercury. Each element, in a representative form, the H
form, is contained in a separate vessel which communicate by a tube.
Over the pure mercury some mercurous sulphate is placed. Both vessels
are filled to above the level of the connecting tube with zinc sulphate
solution, and kept saturated. It is tightly closed or corked. The E. M.
F. at 15° C (59° F.) is 1.438.
Temperature correction
(1 - (.00077 *(t - 15° C) ) )
t being expressed in degrees centigrade (Rayleigh). A diminution in
specific gravity of the zinc solution increases the E. M. F. The cell
polarizes rapidly and the temperature coefficient is considered too
high.
Fig. 80. LATIMER CLARK'S STANDARD CELL.