This is a one fluid battery. The two plates are zinc and carbon. The solution is a solution of iodide of potassium in water, in which iodine is dissolved. The usual strength I use is 1 oz. of iodide of potassium in 2 oz. of water. In this dissolve ½ oz. of iodine, but the strength of the iodine and of the iodide of potassium can be considerably varied without affecting the electromotive force.

The iodine is meant to prevent polarization by uniting with the nascent hydrogen to form hydriodic acid, which will then unite with the caustic potash, to form iodide of potassium and water. In this way the iodide of potassium acts as a carrier of iodine, from the iodine in solution, to the zinc plate.