The Romance of Modern Chemistry

CHEMISTRY AND ELECTRICITY verted into electrical energy, as evidenced by the pro- duction of an electric current. Besides the reaction which has just been discussed, there are many others which have been similarly harnessed. Among the better known electrical cells, which, like the Daniell cell, are devices for transforming the energy of a chemical reaction into electrical energy, are the Grove cell, the bichromate cell, and the Leclanché cell. Another very common form in which chemical energy is stored, ready for conversion into electrical energy, is the secondary cell or accumulator, sometimes called a storage cell. This is a sort of artificial chemical cell, and when complete consists of two lead plates immersed in dilute sulphuric acid, one of the plates, however, being specially prepared and coated with peroxide of lead. In this condition the cell is a store of chemical energy, and when the plates or poles are connected by a wire, a current passes through the latter from the peroxide plate to the lead plate. If much current is taken out of the secondary cell, it gets run down, like the weights in the grandfather’s clock, but like these it can be “wound up” again. This is done by passing through the cell, say from a dynamo, a current of electricity in the opposite direction to that of the current which the cell itself yields. The result of this is to put into the cell a fresh supply of electrical energy, which is there stored as chemical energy ready for immediate use. From what has been said, it will be plain that chemistry has made some very important contributions to the development and application of electricity. This debt, however, has been amply repaid, and any one who studies the modern development of chemistry will be much struck with the part which electricity now 295