SM247      Daniell Cell     circa 1960     Electricity

This type of double fluid cell has an e.m.f. of 1.08 Volts and consists of an amalgamated zinc negative pole in a 5% solution of zinc sulphate (ZnSO₄.6H₂O) or of dilute H₂SO₄.   This is separated by a porous partition from a copper anode in a saturated solution of copper sulphate (CuSO₄.5H₂O).

In supplying a current the zinc electrode goes in solution as zinc sulphate while the copper cation is deposited as metallic copper at the positive electrode.

Since the two solutions have different densities, the Daniell cell can also operate without a porous partition with the CuSO₄ at the bottom.

The e.m.f. of the cell is not affected by polarization and depends on the concentration of the solutions, increasing with an increase of CuSO₄ solution concentration and decreasing with an increase in the concentration of the ZnSO₄ solution.

This was the first form of constant battery and was invented by Daniell in 1836.   It is probably the best of all constant batteries.