paper. The peroxide of the manganese (manganese dioxide) is added to the electrolyte to lengthen the life of the cell by preventing the formation of hydrogen about the carbon electrode.
The paste is sealed into the cell and the carbon electrode is firmly held in place by wax or pitch. This also keeps the cell from drying out.
Ordinary dry cells are capable of producing an electromotive force (e.m.f.) of 1½ volts. A “B” battery consists of a number of primary dry cells connected in series so that the voltage obtainable is the sum of the voltages of the individual cell. We shall learn more about this. Strictly speaking, a single cell should not be called a battery, the word battery meaning a number of cells connected together.
Fig. 8--Cut-away view showing construction of a dry cell.
Fig. 9--Cut-away view showing construction of a 45-Volt B battery.
The old-fashioned wet cells and dry cells that are used at the present time, are called primary cells to distinguish them from the type of cells used in storage batteries, which are called secondary cells. Primary cells cannot be recharged, secondary cells can be. When the chemicals in the primary cells become inactive, the cell is useless--when a secondary battery is run down or discharged, it can be renewed by passing an electric current through it. In other words the electrodes and electrolyte (solutions) are of such materials that there can be no chemical action between them until after the current has first been forced through them.
