Patent GB-191118360-A (GB)
Title: Improvements in or relating to Reversible Galvanic Batteries.
Inventor: MORRISON WILLIAM
IPC: H01M10/24
Filed: 1911-08-14
Granted: 1912-07-11
Abstract: 18,360. Morrison, W. Oct. 10, 1910, [Convention date]. Electrodes; electrolytes. - An alkaline accumulator has the positive electrodes filled with previously-mixed oxides of silver and mercury, and the negative electrodes with a zincchromium-oxygen compound, which may be a chromite, and oxide of mercury, the electrolyte consisting preferably of caustic potash containing a little chromium. On charging, the first part at least of which takes place at a high rate, the active material in the negative electrode is wholly or partly converted into metallic zinc and a potassium-chromium-oxygen compound. On discharging, a concentrated solution of caustic potash is formed in this electrode, and owing to the construction, described below, is retained therein and re-combines with the chromium on charging. The mercury in the negative material serves only for amalgamation ; that in the positive is oxidized and reduced with the silver in charging and discharging. The positive electrode material may be prepared by dissolving 1 part of silver and 5-9 parts of mercury in nitric acid, adding caustic potash, washing the precipitate with hot water preferably containing a little alkali, and then drying. The negative electrode material may be precipitated by adding potash to a solution of the sulphates of zinc and chromium, or it may be prepared by adding a solution of 1 part of chromium sulphate in hot water to 3 parts of zinc oxide suspended in water to form a thin paste, a green precipitate containing zinc, chromium, sulphur, and oxygen, possibly a thiochromite, being produced; on filtering and adding strong hot potash to the precipitate, the zinc-chromium-oxygen compound is formed, and is washed in hot water and dried. Copper supports for the electrode materials are preferred, nickel being unsuitable. The positive material is enclosed between copper sheets 10, 11, Fig. 6, having square tangs projecting at right-angles into the mass; one sheet is filled and another compressed on to it. The negative material, which requires a central conductor in order that action may not be confined to the surface, is packed in a porous sheath impermeable by zinc oxide, for instance a stout paper tube 13, Fig. 8, covered with woven asbestos or its equivalent 14, around a copper rod 15 having washers 19 which divide the sheath into small cells. The sheath is closed by an insulating-plug at each end, and is wound with wire or covered with a perforated metal tube insulated from the central copper rod. Each negative electrode consists of a row of such sheaths connected by clamping their central rods between two metal strips 18, Fig. 4. The electrodes, separated for instance by perforated hard rubber sheets 20, Fig. 4, with longitudinal ribs, are supported by thin tapered cross-bars 7 of rubber or other material spaced on bolts 8 by nuts, in a metal or other cell lined with insulating-material. A connecting-bolt 22 at the top for the electrodes of each sign is attached by a flexible strap 23 to a terminal on the cell cover.