Cup, Porous

A cup used in two-fluid voltaic batteries to keep the solutions separate to some extent. It forms a diaphragm through which diffusion inevitably takes place, but which is considerably retarded, while electrolysis and electrolytic convection take place freely through its walls. As material, unglazed pottery is very generally used. In some batteries the cup is merely a receptacle for the solid depolarizer. Thus, in the Leclanché battery, the cup contains the manganese dioxide and graphite in which the carbon electrode is embedded, but does not separate two solutions, as the battery only uses one. Neverthele , the composition of the solution outside and inside may vary, but such variation is incidental only, and not an e ential of the operation.