Prem Behari Mathur and Nityanandan J. Paul
Central Electrochernicol Research Institute Karaikudi, lndio
1
II
Magnesium Cell for Demonstration
compactness, nonpolarizability, high ampere hour capacity, and simplicity of fabrication are some of the attractive features of the new cell system described here. This cell system consists of copper and magnesium plates or ribbon dipping into copper sulfate solution. A layer of insoluble material develops a t the magnesium electrode as soon as the electrode is dipped in copper sulfate solution. This layer acts as a natural separator between anode and cathode, eliminates short circuiting, and so allows close packing of the electrodes in the cell. The internal resistance and volume of the cell is thus minimized. The copper sulfate solution used here acts as an electrolyte for the magnesium electrode and also as a depolarizor a t the cathode. The cell system does not get polarized a t any rate of drainage of current, and hence it is useful for continuous heavy discharge. Typical data are 6 hr of operation a t 1.1 v a t 100 ma current.' Miniature Cells. Miniature cells can be made out of magnesium plate or magnesium ribbon. Magnesium ribbon can be loosely wound over or within copper articles of different shapes such as a copper washer (Figure la), or a copper or brass thimble (Figure lb), or a plastic sheet (Figure lc). Magnesium ribbon will act as one terminal and a copper wire connected to the copper electrode as the other. On dipping the assembly (la, lb) in CuSOl solution, or filling (lc) with copper sulfate solution in a glass or plastic box, the cell will start functioning. MATTHUR, P. B., in press.
AND
A water activated dry type cell can also be made using anhydrous copper sulfate in the assembly. The salt is not hydroscopic and so the dehydrated salt does not absorb a large enough amount of water to start the chemical reactions with the magnesium in the cell. The shelf life of the cell is therefore kept high. Long Duration Cell. A cell can be made with a bulb fixed on the lid of the container. The cell may be filled with copper sulfate solution, the copper and magnesium terminals connected to the bulb, and the copper electrode dipped in the solution and the magnesium electrode left outside the cell (Figure id). At the time of emergency the magnesium electrode may be inserted into the cell and dipped into the solution. The cell will immediately light the bulb. Magnesium plate or an assembly where a long magnesium ribbon (25-30 in. long) is wound over a plastic sheet can be used in these long duration cells. Some copper sulfate powder can be added to the solution for maintaining the concentration. MATHUR. P. B..
AND
PAUL,N. J., J . Sci. Indwtr. Res.,
PAUL,N. J., Indian J . Appl. Chem., Figure 1.
Miniature cells
Volume 40, Number I , January 1963
/
43
