Mr Kemp on a New of Kind Galvanic Pile. 73 



it decomposes imperfect cowductors, mu3t be acknowledged to be of some im- 

 portance. 



AB, CD, Fig. 1. Plate II. represents a circular wooden cup half an inch in 

 depth, and three in diameter, having a projecting rim AB. H is a small button 

 of wood turned on the bottom of the cup at its centre, and which projects one- 

 eighth of an inch from it. EF is a circular plate of copper attached to the cup, 

 by means of a wire of the same metal, on which a screw is formed. The wire 

 passes through the cup, and screws into a brass nut I, Fig. 3., which is sunk 

 into the inside of it ; the copper plate being kept at its proper distance by the 

 button of wood. The whole is rendered tight by a coating of wax, care being 

 taken to keep the nut and the projecting point of the wire free from wax. 



The copper plate EF, Fig. 2. is perforated with holes, to allow the hydro- 

 gen, as it is formed at the surface of the zinc and mercury, to pass up through 

 it and escape, which would otherwise collect into a globule at its under surface, 

 and force the water over the edge of the cups, and destroy the action of the 

 pile. A plate of wire-gauze, or a copper wire coiled round so as to form a 

 plate, will answer the purpose equally well, as it allows the hydrogen to pass 

 freely through its interstices, at the same time that it presents a favourable sur- 

 face for conducting the fluid. 



A quantity of the liquid amalgam of zinc and mercury, merely sufficient to 

 cover the bottom, is to be poured into the cup, which will be in contact with 

 the copper plate EF, through the medium of the nut and wire ; over this is 

 poured as much diluted muriatic acid as will nearly fill the cup. In this 

 manner we have obtained one complete plate, consisting of copper, the amal- 

 gam of mercury and zinc, and acid, and, by continuing the series, they may be 

 increased to any extent. 



In this arrangement, the amalgam of zinc and mercury becomes the posi- 

 tive plate, while the copper is rendered negative. 



For the purpose of experimenting with this apparatus, the amalgam (rf 

 mercury and zinc having been poured into the cups as stated, they are to be 

 placed above each other as appears in Fig. 4. ; the undermost plate of 

 which becomes the negative pole, and the uppermost the positive. The cir- 

 cuit is formed the same as in the pile already described. 



The formation of the amalgam of mercury and zinc, which is used as the 

 positive plate in this arrangement, is easily effected, and the preparation only 

 occupies a few minutes. A quantity of zinc in fragments being put into a 

 crucible, over which is poured about four or five times its weight of mercury, 

 and heat applied to it by a common fire, when the mercury arrives at its 

 boiling point, the zinc will be found to be completely dissolved. To this 

 composition, while warm, any quantity of mercury may be added, which will 

 combine with it, in the same manner as if it had been heated along with it in 

 the crucible. 



The amalgam, when once prepared, is fit for use as long as any of the zinc 

 remains in the solution ; and as the quantity dissolved at each time by the acid 

 is very small, the same amalgam may be employed for a considerable time: 

 and, indeed, so long as a particle of zinc remains in combination with the mer- 

 cury. When the whole is dissolved, the mercury is left in a perfectly pure 



