Many devices which will change alternating current to a direct current have been put on the market, but probably there is not one of which suits the amateur's needs and pocketbook better than the electrolytic rectifier.
Electrolytic Rectifier and Connections
For the construction of such a rectifier four 2-qt. fruit jars are required. In each place two electrodes, one of lead and one of aluminum. The immersed surface of the aluminum should be about 15 sq. in. and the lead 24 sq. in. The immersed surface of the lead being greater than that of the aluminum, the lead will have to be crimped as shown in Fig, 1. In both Fig. 1 and 2, the lead is indicated by L and the aluminum by A. The solution with which each jar is to be filled consists of the following:
Water 2 qt.
Sodium Carbonate 2 tablespoonfuls
Alum 3 tablespoonfuls
Care should be taken to leave the connections made as shown in Fig. 2. The alternating current comes in on the wires as shown, and the direct current is taken from the point indicated.
The capacity of this rectifier is from 3 to 5 amperes, which is sufficient for charging small storage batteries, running small motors and lighting small lamps. --Contributed by J. H. Crawford, Schenectady, N. Y.