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Galvanic Tinning

M. Maistrasse-Dupré, it appears, had been commissioned by the French government to apply, by galvanic means, tin upon divers objects which had been made of so-called galvanized iron-that is, iron covered with zinc. To Electroplating lectroplating with Various

Metals. The following purpose he applied galvanic elements made of receipts furnish the means of coating objects copper and zinc plates, the length of which is with tin, zinc, brass, German silver, and other 48 inches, the width 28 inches, placed in a leaden trough and separated and isolated by metals.

3749. To Electroplate Copper, Brass, means of wooden partitions. The copper or German Silver, with Aluminum, sheet was immersed in a mixture of equal take equal measures of sulphuric acid and parts of acetate of lead and common salt, and water, or take 1 measure each sulphuric and the zinc element was placed in weak sulphuric hydrochloric acids and 2 measures water; add acid, specific gravity 1.060. This battery reto the water a small quantity of pipe-clay, in mains in constant action and working order the proportion of 5 or 10 grains by weight to for 8 days, at an outlay of only 2 francs. every ounce by measure of water (or ounce When the objects which are galvanically to the pint). Rub the clay with the water until tinned are afterwards heated to the melting the two are perfectly mixed, then add the acid point of tin, the goodness and durability of to the clay solution, and boil the mixture in a hot-tinned materials is thus obtained. Copper covered glass vessel 1 hour. Allow the liquid thus tinned (galvanically), and afterwards to settle, take the clear, supernatant solution, heated, is superficially converted into bell while hot, and immerse in it an earthen por- metal, while the method of tinning galvanous cell, containing a mixture of one measure ically has the great advantage over the old of sulphuric acid and ten measures of water, method, that it can be applied to objects to together with a rod or plate of amalgamated which the method of tinning in ordinary use zinc; take a small Smee's battery of 3 or 4 is not applicable. cells, and connect its positive pole by a wire

3752. Το Electroplate with Brass. with the piece of zinc in the porous cell. Brass can be deposited when the solution is Having perfectly cleaned the surface of the composed of 1 part sulphate of copper in 4 article to be coated, connect it by a wire with parts hot water, 8 parts sulphate of zinc in 16 the negative pole of the battery, and immerse parts of hot water, 18 parts cyanide of potasit in the hot clay solution; immediately sium in 36 parts of hot water. These are abundance of gas will be evolved from the mixed, and 250 parts of water added. Instead whole of the immersed surface of the article, of a copper positive electrode plate, one of and in a few minutes, if the size of the article brass is necessary; the solution is required to be kept nearly boiling, and a powerful battery to be used. 3753. To Prepare Cyanides of Copper and Zinc. For copper, dissolve 1 ounce of sulphate of copper in 1 pint of hot water.

For zinc, dissolve 1 ounce of the sulphate of zinc in 1 pint of hot water, and proceed the same as for cyanide of silver. (See No. 3697.) 3754. Cyanide Solution of Copper or Zinc. Dissolve 8 ounces (troy) cyanide of potassium, and 3 ounces cyanide of copper or zinc in 1 gallon of rain or distilled water.

They should be used at about 160° Fahr.; with a compound battery of 3 to 12 cells. is adapted to the quantity of the current of electricity passing through it; a fine white deposit of aluminum will appear all over the surface. It may then be taken out, washed quickly in clean water, and wiped dry, and polished; but if a thicker coating is required, it must be taken out when the deposit becomes dull in appearance, washed, dried, polished, and reimmersed; and this must be repeated at intervals, as often as it becomes dull, until the required thickness is obtained.

With small articles it is not absolutely necessary that a separate battery be employed, as the article to be coated may be connected, as in the one cell method (see No. 3669), by a