The German scientist Johann Christian Poggendorff overcame the problems with separating the electrolyte and the depolariser using a porous earthenware pot in 1842. In the Poggendorff cell, sometimes called Grenet Cell due to the works of Eugene Grenet around 1859, the electrolyte is dilute sulphuric acid and the depolariser is chromic acid. The two acids are physically mixed together, eliminating the porous pot. The positive electrode (cathode) is two carbon plates, with a zinc plate (negative or anode) positioned between them. Because of the tendency of the acid mixture to react with the zinc, a mechanism is provided to raise the zinc electrode clear of the acids.