The electromotive force is 1.5 volts, current of the No. 7 size on short circuit, 24 amperes. Nos. 2, 5, 6, or 7 are most suitable for electric gas lighting, either by simple primary coil or jump spark coil.
The Edison Lalande Cell.
This cell (Fig. 55), gives a large, steady current and is of low internal resistance, but its electromotive force is not high, being less than .7 volt on closed circuit. Its output of current varies with the size, type S being .025 ohm internal resistance and capacity of 300 ampere-hours. The Edison Lalande cell can be applied to electric gas lighting in cases where a large demand is made upon the battery, for example in church or theatre lighting.
Its elements consist of positive plates of amalgamated zinc suspended on each side of negative plates of black oxide of copper. The electrolyte is an aqueous solution of caustic soda. A layer of heavy paraffin oil is poured on top of the solution to prevent the solution from evaporating and also to keep the soda crystals from creeping up and over the rim of the jar.
Fig. 55.
To set up an Edison Lalande cell, fill the jar up to the brown mark with clear water; pour in the soda from the tin box, and stir. When thoroughly dissolved, pour on top of the solution one half-inch layer of the oil which is sent with the battery. Then the elements attached to the cover can be inserted, and the cell is ready for use.
Use care not to splash the solution, as it will burn the clothing and skin. If any does get on, a little animal grease or vegetable oil will quickly saponify it.
In the action of this cell the oxide of copper is reduced to metallic copper and the zincs consumed, it being intended that each element will require renewal at the same time. Upon picking into the oxide plate with a sharp-pointed instrument, if the plate is red throughout, it is exhausted; but, should it show black in its interior, it is still capable of a little more use, but is preferable to use a new plate whenever there is but little oxide left.
Never remove the oxide plates from the battery, and do not allow the solution to be less than one inch above oxide plates.