Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . yet CTRO — GILDING AND SILVERING. 61 almost impracticable to reduce platinum in otherthan the divided state, which has, however, an im-portant application in the coating of platinum platesfor batteries, where it prevents the adhesion ofhydrogen. The solution used for this purpose is thechloride obtained by dissolving platinum in nitro-muriatic acid, and partially evaporating to expel anygreat excess of acid. The solution may be subse-quently dilu
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . yet CTRO — GILDING AND SILVERING. 61 almost impracticable to reduce platinum in otherthan the divided state, which has, however, an im-portant application in the coating of platinum platesfor batteries, where it prevents the adhesion ofhydrogen. The solution used for this purpose is thechloride obtained by dissolving platinum in nitro-muriatic acid, and partially evaporating to expel anygreat excess of acid. The solution may be subse-quently diluted to any required amount. 98. The battery used for gilding and silveringconsists of from three to six or eight pairs, accordingto the extent of surface to be covered, and the resist-ance offered by the solution. As the solutions growolder, they require less power to decompose them ibut there is then a greater tendency to the blackdeposit. The positive pole usually employed is aplatinum wire, or pointed strip of platinum is not dissolved by the solution, and conse-quently the electro-negative element of the salt has Fig. to be evolved, instead of entering into a new com-bination. It is on this account that several pairshave no more efficiency in decomposing the solu-tion than one pair where the positive pole is dis-solved. The object of the present arrangement is6 62 DAVISS MANUAL. to bring the whole action more exclusively underthe control of the battery, and to avoid local ordinary purposes, a Smees battery, weaklycharged, is preferable. Fig. 34 represents an oddsand ends battery of this kind, connected with thesilvering apparatus, differing only from that describedin 89 by being uncovered. It will be observedthat the positive pole, in the decomposing cell, isplaced at a distance from the object to be Another form of Smees battery, connectedwith a depositing apparatus for silvering daguerreo-type plates, is exhibited in Fig. 35. This
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
