 Alfred Dun 1885, nitro-muriatic acid ("aqua regis") - Iron & Carbon
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.