Woodward Battery

A Novel Form of Primary Battery.

In a battery recently invented by Mr. Henry Woodward advantage is taken of the depolarizing property of the oxide of copper in the construction of a cell which shall retain its E. M. F. constant. The cell, which is shown in the accompanying engraving, Fig. 1, has a negative element of peculiar construction and the positive electrode is constructed of zinc sponge. The negative element B is made by taking a piece of iron of requisite size and shape, placing around it a jacket C of perforated iron, and filling the space between the casing and the piece of iron with oxide of copper and iron filings, or turnings D. By this construction a large and good conducting surface is secured, while rapid polarization is prevented. The electrode is placed in a cauatic-potash solution in a cell with the zinc sponge element.

In another form of cell designed by Mr. Woodward, the object has been to obtain a battery of high E. M. F., and which shall at the same time be of low cost. This cell, which is shown in Fig. 2, consists of an outer jar A, in the centre of which is placed a porous cup a, containing a series of zinc plates a', these plates being connected together in order to present as large a surface as possible. In this cup is placed a solution of sea-salt, Epsom salt or caustic potash, the latter, however, being most efficient.

To make the caustic-potash solution, a sufficient quantity of crude potash is boiled in water until the water is thoroughly saturated, which requires about three hours, when there is added a paste made of lime, and the whole is then boiled for about two hours longer, after which it is strained. It is then ready for use. The outer jar B is filled with broken pieces of carbon, in which is placed a carbon plate b. Upon this carbon plate is poured a strong solution of chromic acid.

This combination, it is claimed, yields a comparatively high electromotive force.

Figs. 1 and 2. — the Woodward Primary Battery.