ELECTRO-METALLURGY.

83

Practice of making medals, Sc c., of copper. I should imagine that the black oxide of?°pper dissolved in solution of cyanide of potassium would answer better; as the ironln the ferrocyanide might be rather injurious. The iron to be coppered being previously' Ve U cleaned from rust, &c., with the aid of a dilute acid, is to be plunged into thecyanide solution heated*to 120° Fahrenheit, and connected by a wire with the negativePole of a voltaic battery, as formerly described. In from five to ten minutes, the iron'^dl be completely coated. It is then to be scoured with sand, and plunged into solutionsulphate of copper; whereby it will show black spots wherever there are any defec-places. In this case, it is to be cleaned and replaced under the cyanide solutiou,^ the decomposition cell for a minute or two. Zinc may be deposited from a solutionits sulphate by a like arrangement.

•Metallic tdoth may be made as follows :—On a plate of copper attach quite smoothly* stout linen, cotton, or woollen cloth, and connect the plate, with the negative pole ofa . v oltaic battery; then immerse it in a solution of copper or other metal, connecting ajhece of the same metal as that in the solution with the positive pole; decomposition‘jkes place,* and the separated metallic particles in their progress toward the metalPjute or negative pole, insinuate themselves into the pores of the tissue, and form a coin-Nete sheet of flexible metal. Lace is metallized by coating it with plumbago, and thenObjecting it to the electro-metallurgic process.

. The gilding solution should be used in the electric process at a temperature ofo0° F, The more intense the electric power, the denser and harder is the metallicc °at deposited.

Metallic silver may be combined with cyanogen by subjecting it to the joint actiona solution of cyanide of potassium and positive electricity. Or cyanide of silver may. e precipitated from the nitrate by a little cyanide of potassium, and afterward dissolvedy means of an excess of cyanide of potassium. The quantity of electric power or sur-acc-size of the battery should in all cases be proportioned to the surface of the articles0 be placed or gilt, and the electric intensity or number of sets of jars proportioned tohe density of the solution. Plating is accomplished in from 4 to 6 hours. The articless hould be weighed before and after this operation, to ascertain how much silver theyW taken on” ,

Messrs. Elkington make their moulds with wax, combined with a little phosphorus,v hich reduces upon their surfaces a thin film of gold or silver, from solutions of these.° e tals, which films are better than the blackleaded surfaces for receiving the copperae Posite. They also recommend to add a little alkali to the solution of sulphate of.°Pper, intended to afford a deposit? of metal. The single cell, first described above,best adapted for this purpose.

. M. Rnolz employs for gilding, a solution of sulphuret of gold in sulphuret of potas-hm, which he prepares by precipitating a solution of gold in aqua regia, by sulphu-.Jated hydrogen, and redissolving the precipitate with sulphuret of potassium. By

the

Use of this solution of gold, he obtains a very beautiful and solid gilding, and at less

^ x Pense than with cyanide of potassium. Every metal which is a negative electrode ton m . a y be gtM«l.

: "latinizing is effected best by means of a solution of the potash-chloride of platinum11 caustic potash. 1 milligramme (0-015 grain) covers completely a surface of 50JlPare centimeters (2 inches square); the film of platinum is only one hundredth of a^gramme thick.

j. M. Boettger has shown that we may easily tin copper and brass in the moist way by* s solving peroxide of tin (putty) in hydrate of potash (caustic potash ley), putting atc e bottom of the vessel holding that solution some turnings of tin, setting the piece ofJ^her or brass upon the turnings, and making the liquor boil. An electric current is°duced by the contact of the dissimilar metals; and as the tin is withdrawn by the,j® p Pw or brass from the solution, it is restored to it by the turnings. Zinking may be, ne in the same way ; by putting pieces of zinc into a concentrated solution of chlorine,to the piece of metal to he zinked in contact with these pieces, and applying heat

the vessel containing the whole.

j*or certain new methods of constructing and arranging voltaic batteries for electro-etallurgic operations, a patent was obtained by .Dr. Leeson ip June, 1842.

*£• 42, is a longitudinal section of the battery, and jig. 43, a plan view of the framea tvhich the metal plates are attached, a is a rectangular wooden trough, containingce ]T°°den frame b, formed with vertical grooves in its sides, to receive a series of porous, ‘I s c, c, c. The plates of the battery are suspended in the fluid or fluids by brassne f ?’ d ’ fast ened t0 a wooden frame e, e, which rests upon the trough a, and is con-out c t0 tbe other frame b, by two pins/, when they are required to be raised togetherthe trough a, a.

1 be battery may be charged as usual with one or two fluids ; one of them in the latter