A HOME-MADE DRY-CELL*
Procedure A strip of zinc two inches wide and three inches long was folded so that it formed a triangular box one inch wide and two inches high. A threecornered piece of zinc was then fitted in to form the bottom. The box was next filled with a mixture of two-thirds ammonium chloride (sal ammoniac), one-sixth manganese dioxide and one-sixth granulated carbon, i. e., powdered charcoal. A copper strip was then introduced into the center of the zinc case containing the above chemicals, care being taken that the copper strip did not touch the zinc case in any place. Chemical ingredients The chemicals in the zinc case were then moistened. Copper strippositive
Zinc casenegative
Explanation The sal ammoniac acted on the zinc, the manganese dioxide prevented polari+ion or the gathering of hydrogen bubbles on the copper strip as it united with Hem to form water, and the carbon kept the mixture porous. Conclusion
This battery, although so very small (oneby twoinches),when tested with a voltmeter showed one volt and registered half an ampere on an ammeter. In order to get a current from this cell it was of course necessary to complete the circuit by attaching a wire to the positive pole, thecopperstrip, and also a wire to the negative pole, the zinc case. This cell has no practical value but it was made by a high-school student to demonstrate the theory. Any other student can improve his standing somewhat by making one if it coincides with his school studies. *Winner of five-dollar award in student contest closing March 15, 1929.
