A Useful Electric Cell

Abstract

TAKE a glass vessel, a porous cell, a zinc rod and a carbon plate, such as are used in the ordinary Leclanché cell (a circular glass vessel of the same capacity is better). Prepare a solution of 20.4 grams of potassium dichromate and 87.4 grams of sulphuric acid (sp. gr. 1.75) in 350 grams of water and pour it into the glass vessel. Place the carbon plate in this solution. Fill the porous cell with a solution of 14.5 gm. of ammonium chloride in 200 gm. of water and place it in the glass vessel containing the dichromate solution. The amalgamated zinc rod is placed in the porous cell. The E.M.F. of this cell is 2 volts. The internal resistance is about 0.6 to 0.8 ohm. When continuqusly used, it gives a constant current for more than 12 hours, and the E.M.F. remains unchanged. The rate of dissolution of zinc (when a rod of zinc is used) is only 2.5 gm. in 12 hours, while in the bichromate cell the rate is 12 gm. When used intermittently, the cell remains efficient for more than three weeks.