Home › Electroplating With Various Metals › To Electroplate with Tin

To Electroplate with Tin

Tin purposes is as follows: To a solution of sulis easily deposited from a solution of proto- phate of copper, add a solution of ferrocyanide chloride of tin. If the two poles or electrodes of potassium (yellow prussiate of potassa), be kept about 2 inches apart, a most beautiful so long as a precipitate continues to be formphenomenon may be observed. The decom- ed; this is allowed to settle, and, the clear position of the solution is so rapid that it liquor being decanted, the vessel is filled with water, and when the precipitate settles, the 3758. Test for Galvanized Iron. liquor is again decanted, and these washings When zinc is deposited on iron by galvanic are repeated until the sulphate of potash is agency, it should form a chemical combination washed quite out. This is known by adding with the iron, and not be merely attached a little chloride of barium to a small quantity thereto. It is proposed by Mr. T. Bruce of the washings; if no white precipitate is Warren, of England, to use this fact for pracformed by this test, the precipitate is suffi- tically testing the efficiency of the galvanizaciently washed. A solution of cyanide of tion. If mercury be poured over the surface, potassium is now added to this precipitate the zinc that is only locally attached will until it is dissolved, during which process the form an amalgam with the mercury. M. solution becomes warm by the chemical reaction that takes place. The solution is filtered, and allowed to repose all night. If the solution of cyanide of potassium that is used is strong, the greater portion of the ferrocyanide of potassium crystallizes in the solution, and may be collected and preserved for use again.

If the solution of cyanide of potassium used to dissolve the precipitate is dilute, it will be necessary to condense the liquor by evaporation, to obtain the yellow prussiate in crys- Warren also uses this as a quantitative test, to verify the amount of zinc in combination with the iron.

3759. Το Make a Cyanide Solution of Brass. Dissolve 1 pound (troy) cyanide of potassium, 2 ounces cyanide of copper, and 1 ounce cyanide of zinc, in 1 gallon rain or distilled water; then add 2 ounces muriate of ammonia. This solution is to be used at 160° Fahr. on smooth work, with a compound battery of 3 to 12 cells. tals; the remaining solution is the coppering 3760. Electroplating with Platinum. solution. Should it not be convenient to This metal has never yet been successfully separate the yellow prussiate by crystalliza- deposited as a protecting coating to other tion, the presence of that salt in the solution metals. A solution may be made by dissolvdoes not interfere with its power of depositing ing it in a mixture of nitric and muriatic acids, the same as is employed in dissolving copper.

3756. To Prepare Iron for Coating gold; but heat must be applied. The soluwith Copper. When it is required to cover tion is then evaporated to dryness, and to the an iron article with copper, it is first steeped remaining mass is added a solution of cyanide in hot caustic potash or soda, to remove any of potassium; next, it must be slightly heated grease or oil. Being washed from that, it is placed for a short time in dilute sulphuric acid, consisting of about 1 part of acid to 16 parts water, which removes any oxide that may exist. It is then washed in water, and scoured with sand till the surface is perfectly clean, and finally attached to the battery, and immersed in the cyanide solution. (Sce No. 3755.) All this must be done with dispatch, so as to prevent the iron combining with for a short time, and then filtered. This solution, evaporated, yields beautiful crystals of cyanide of platinum and potassium; but it is unnecessary to crystallize the salt. A very weak battery power is required to deposit the, metal; the solution should be heated to 100°.

Great care must be taken to obtain a fine metallic deposit; indeed, the operator may not succeed once in twenty times in getting more than a mere coloring of metal over the oxygen. An immersion of five minutes' dura- surface, and that not very adhesive. The tion in the cyanide solution is sufficient to causes of the difficulty are probably these: deposit upon the iron a film of copper. But the platinum used as an electrode is not acted it is necessary to the complete protection of upon; the quantity of salt in solution is very the iron, that it should have a tolerably thick little; it requires a particular battery strength coating; and, as the cyanide process is expen- to give a good deposit, and the slightest sive, it is preferable, when the iron has re- strength beyond this gives a black deposit; ceived a film of copper by the cyanide solu- so that, were the proper relations obtained, tion, to take it out, wash it in water, and whenever there is any deposit, the relations attach it to a single cell or weak battery, and of battery and solution are changed, and the put it into a solution of sulphate of copper. black pulverulent deposit follows. If there is any part not sufficiently covered