Name.

Electrodes.

Solutions.

E.M.F.

Clark.

Pure mercury and pure zinc.

The mercury is covered with a paste of mercurous sulphate and a saturated solution of zinc sulphate, in which is placed the rod of zinc.

1.434 at 15° C. at any temp t° C. it is

1.434[l-.0008(t° - 15°)].

Daniell.

Copper and zinc.

The zinc is immersed in a solution of zinc sulphate, and the copper in a solution of copper sulphate.

Depends upon the densities of the solutions; it varies from 1.07 to 1.14 volts.

Groves.

Platinum and zinc.

The platinum is immersed in a strong nitric acid, and the zinc in dilute sulphuric acid.

About 1.93 volts.

Bunsen.

Carbon and zinc.

The carbon in nitric acid, and the zinc in dilute sulphuric acid.

About 1.74 volts.

Leclanche.

Carbon and zinc.

The carbon is packed in a porous pot with peroxide of manganese and broken gas carbon. The zinc is immersed in solution of sal ammoniac.

About 1.47 volts; but is quickly reduced if used to send a strong current.

Potash - bichromate.

Carbon and zinc.

The best solution is 1 lb. of potassium-bichromate, 2 lbs. strong sulphuric acid sp. gr. 1.836, and 12 lbs. water, in which both electrodes are immersed, the zinc being withdrawn when the cell is not in use.

About 2 volts; but is quickly reduced if employed to send a strong current.