Practical Daniell Cell

—An inexpensive and easily made form of Daniell cell consists of a U-shaped tube with a little cotton pushed down to the bott on of the bend to form the porous partition. A saturated solution of sulphate of copper is put into. one leg of the tube and a solution of sulphate of zine in the other. The positive plate consists of a rod of chemically pure zine and the negative plate is a rod of pure copper. These rods are inserted through corks which are placed in the tube ends. Such a cell can be put together in a few minutes and gives a reliable standard of electromotive force, good enough for ordinary work, the current, however, is smal” compared to the usual form of Daniell cell.