In the new element there can be used advantageously as exciting-liquid in the first case such solutions as have in a concentrated condition great depolarizing-power, which effect the whole depolarization chemically without necessitating the mechanical expedient of increased carbon surface. It is preferred to use iron as the positive electrode, and as exciting-liquid nitro muriatic acid (aqua regis), the mixture consisting of muriatic and nitric acids. The nitro-muriatic acid, as explained above, serves for filling both cells. For the carbon-cells it is used strong or very slightly diluted, but for the other cells very diluted, (about one-twentieth, or at the most one-tenth). The element containing in one cell carbon and concentrated nitro-muriatic acid and in the other cell iron and dilute nitro-muriatic acid remains constant for at least twenty hours when employed for electric incandescent lighting.