IX. On a new form of voltaic battery

Abstract

The battery which I have the honour to bring under the notice of the Royal Society is one of high electromotive force, namely, about two and three quarter volts, and a single cell consequently decomposes water; it is very light and portable, and convenient for many purposes. The electro-positive element is sodium, the electro-negative element is either carbon, spongy platinum,copper, or other metallic gauze; no fluid is used in which to immerse the plates, but the atmospheric air which is always impregnated with more or less hygrometric moisture serves to set up the action of the battery by giving up sufficient moisture to wet the surface of the sodium, so that a very thin film of fluid (a solution of soda), is thus interposed between the sodium and electro-negative element, and the internal resistance is very small in consequence of the thinness of the film of fluid. The sodium is used in the form of plates, conveniently about a quarter of an inch thick, and the plates of carbon, of which one is placed on each side of the sodium, a little longer and about the same thickness as the sodium; these plates, carbon, sodium, carbon, are kept together by means of vulcanised rubber bands, and suspended vertically, a vessel being placed underneath to receive the soda solution as it forms. A battery composed of plates 10 inches long and ½ an inch wide gives a current of 0·122 ampére at first starting, but as polarisation takes place, after five minutes, only 0·079 ampère. The cost of a battery of this size is 0·40 fr. (4 d . about), it remains in action for six days without the renewal of the sodium. Batteries of larger dimensions, as for example 10 inches long and 15/8 inches wide, last four weeks, because the action is chiefly on the edges of the sodium plate, and the broader the plate the longer the sodium lasts without renewal.