4.—Porous cells should be examined, and cracked ones replaced.
5.—No sulphate of zinc or dirt should be allowed to collect at the lips of the cells.
In the case of a Daniell battery—
1.—The solutions should be inspected daily, and crystals of sulphate of copper added as required.
2.—The zinc plate must not touch the porous cell, or copper will be deposited on it (the zinc).
3.—The battery should be charged with sulphate of zinc from the first.
4.—The copper solution must be watched and prevented from rising over the edge of the porous jar, the tendency of such solutions being to mix with each other by an action termed osmosis.
These being in addition to foregoing general directions for Voltaic batteries.
Defects in a Voltaic Battery on its Current becoming Deficient.—On the electric current of a Voltaic battery becoming deficient, the following defects should be looked for:—
1.—Solutions exhausted; for instance, sulphate of copper in a Daniell's entirely or nearly gone, leaving a colourless solution.