196 ANNUAL OF SCIENTIFIC DISCOVERY. 



tion of common salt between two metals, iron and copper, connected 

 together in a voltaic battery ; the salt is decomposed at the expense of 

 the iron, its chlorine combining with the metal to form chloride of iron, 

 whilst the sodium enters into combination with the oxygen of the 

 water, forming caustic soda ; the other constituent of the water, the 

 hydrogen, passing off in the gaseous state. The caustic soda thus pro- 

 duced goes in the direction of the copper, and, in order to prevent the 

 -amalgamation of the two solutions, (chloride of iron and caustic soda,) 

 a diaphragm, constructed of some suitable porous material, is placed 

 between the iron and the copper, the solution of salt being placed in 

 that part of the apparatus used to contain the iron, and clean water 

 put on the sides in which the copper is situated, in order to receive the 

 caustic soda produced by the decomposition of the salt. In order to 

 insure the decomposition of the salt, two conditions are essential to be 

 observed, viz., that the temperature of the saline solution be between 

 70 and 150 Fah., and the access of the atmospheric air prevented; 

 other wise the chloride of iron will become converted into oxide, and the 

 salt be recomposed as fast as it is decomposed, thus rendering the pro- 

 cess of no utility. 



The following details are given by the patentee for the manufacture 

 of a ton of soda-ash, according to his process : For this purpose a 

 cistern or tank is constructed of stone, slate, or other suitable material, 

 not liable to be acted upon by caustic soda, the dimensions of which are 

 eleven feet long, six feet wide, and three feet deep. It is divided into 

 three compartments, by means of diaphragms, formed of some suitable 

 porous material, such as biscuitware or unglazed earthenware. These 

 diaphragms run the full length of the cistern, and are so placed, that 

 the middle compartment is one foot wide, and the two outer compart- 

 ments each 2 feet in width. The cistern being thus ready for use, 

 pigs of Scotch iron are placed in the two outer divisions or compart- 

 ments of the cistern or tank, in such a manner that the salt water may 

 touch as much of their surfaces as possible. A small portion of each 

 pig of iron is also filed bright, so that perfect metallic contact between 

 each piece of iron may be ensured, by placing the bright part of the 

 pig in connection with the bright part of the one next adjoining. 



The number of pieces of iron employed to be as many as will leave 

 room for the addition of 324 gallons of salt water, which must next be 

 placed in each of the compartments containing iron. Two plates of 

 copper, of the same dimensions as the length and depth of the cistern, 

 are to be placed at each of the two porous diaphragms, at a distance 

 of a quarter of an inch from them. Either copper foil or copper plate, 

 of any thickness, may be employed for this purpose, as surface only is 

 required, no action on the copper taking place in the process. Each 

 piece of copper must be connected with the pig of iron nearest to it, 

 by means of a strip of copper bent over the diaphragm, and fastened 

 by means of a screw, or other suitable means, in connection with the 

 bright part of one of the pieces of iron in the outer compartments, with 

 a view of ensuring that full metallic contact which is necessary for the 

 success of the operation. For the manufacture of a ton of soda-ash, a 

 solution of 2,489 pounds of salt in 474 gallons of water is employed, 



