DILUTION OF LITHIUM CHLORIDE 
513 
On -passing the current from a single lead accumulator for one 
to two minutes there is formed a closely adhering, reddish brown 
deposit of silver chloride. For any one series of measurements, 
the silver chloride electrodes were always first checked against 
each other. This was done by grouping them in a dilute solu- 
tion of hydrochloric acid and observing the potential differences 
between each electrode and another similar electrode taken as 
a standard. Only those varying by less than .05 millivolts were 
chosen. Two or three of these electrodes were then placed in 
each half-cell. After they had been in contact with their re- 
spective solutions for four or five hours, each electrode was re- 
eheeked against those in the other half-cell. Unless at least two 
electrodes in each half-cell differed by less than .02 millivolts, 
the cell was disconnected and the electrodes replated. 
Form of cell. — It was desired to measure the electromotive 
forces of two combinations, viz., one involving transference, 
Ag — AgCl j Li Cl n" j | LiCl n' | AgCl— Ag, 
the other without transference, 
Ag— AgCl | LiCl n' — LiCl n ' (LiHg x )- (LiHgx ) LiCl n'-LiCl ri | AgCl-Ag 
The form of cell adopted was such that both of these combina- 
tions could be obtained from a single set-up of the apparatus. 
Two half-cells, each having two side-tubes and containing solu- 
tions of the desired concentrations in contact with the silver 
chloride electrodes, were so arranged that from one set of side- 
tubes a. liquid junction could be made and the first combination 
thus obtained. The other set of side-tubes were thus left free 
for liquid connection with small cells', into which dipped the 
amalgam electrodes, thereby forming the cell without transfer- 
ence. Liquid contact between the half-cells was effected by 
means of an inverted T-tube fitted with a three-way stop-cock. 
To further prevent diffusion loose plugs of cotton were inserted 
into the bore of these stop-cocks. Fresh liquid contacts were 
readily made by drawing more of each solution into the free 
limb of the T-tube. For cells with transference it is essential 
that a sharp boundary be produced between the solutions im- 
mediately before measurements are made. It was found that 
the electromotive force of the cells directly connected remained 
constant for several days when this precaution was observed. 
33 
