METALH-C soLtiTioxs.] UNDULATORY FORCES. ELECTRO-METALLURGY. 



221 



111. Mr. Joseph Steele coats zinc, iron, steel, copper, 

 and brass, with tin, in his patent solution, by the 

 battery process, thus: Dissolve 60 pounds of common 

 soda, 15 pounds of pearl-ash, 5 pounds of caustic potash, 

 and 2 ounces of cyanide of potassium, in 75 gallons of 

 water, at 75 Fah., and filter the mixture so made; 

 then add 2 ounces of acetate of zinc, and 16 pounds of 

 binoxide of tin; stir the resulting solution until all is 

 dissolved; it is then ready for use. Work it by the 

 battery process with an anode of zinc or tin, and with 

 the liquid at 75 Fah. 



112. Electrical Relations of Tin and Iron. Tin is feebly 

 negative to iron at all temperatures between 62 and 

 203 Fah. in distilled water, and positive to it at 212 

 Fah. It is positive to iron at all temperatures between 

 62 and 212 Fah. in a saturated solution of boracic 

 acid; also the same between those temperatures in a 

 strong solution of phosphoric acid in distilled water ; or 

 in one measure of oil of vitriol mixed with either nine or 

 ninety-six measures of distilled water ; or in a mixture 

 of one measure of this acid, and 192 measures of dis- 

 tilled water, from 73 to 158 Fah. , and negative to iron 

 above that to 2ft Fah. It is positive to iron from 72 

 to 212 Fah. in a mixture of equal measures of hydro- 

 chloric acid and water ; it is negative to iron from 70 to 



Fah. , and positive above that to 212 Fah. , in a 

 mixture of one measure of hydrochloric acid and nine 

 measures of distilled water ; it is negative to iron from 

 70 to 212 Fah. in a mixture of one measure of hy- 

 drochloric acid, and ninety measures of distilled water ; 

 and positive to iron from 68 to 212 Fah. in one 

 measure of hydrofluoric acid and nine measures of water ; 

 it is positive to iron in one measure of nitric acid and 

 nine measures of water from 70 to 111 Fah., and 

 negative from 111 to 212 Fah. ; and it is positive to 

 iron from 82 to 212 Fah. in a mixture of one measure 

 of nitric acid and ninety-six measures of water. 



113. Lead Salts. The most common salts of lead arc 

 the nitrate, and the acetate. The nitrate is formed by 

 dissolving lead in dilute nitric acid, taking care that no 

 more lead is added than the acid will dissolve ; the re- 

 sulting solution must be filtered, evaporated, and crys- 

 tallised ; it is a hard, white salt, soluble in water. 

 Acetate of lead is made by digesting oxide of lead in 

 vinegar or acetic acid; filtering, evaporating, and crys- 

 tallising the liquid : it is soluble in water. 



114. Lead Solution. Lead may be deposited from an 

 aqueous solution, either of nitrate or acetate of lead, or 

 from a solution of plumbite of potash : the hitter is 

 formed by dissolving litharge in a boiling solution of 

 caustic potash. Zinc and tin articles (but not iron) 

 decompose this liquid, and coat themselves with lead in 

 it, by simple immersion. It is difficult to deposit any 

 considerable thickness of reguline metal from either of 

 these liquids. 



115. Salts of Iron. Among the salts of iron in most 

 common use, are the sulphate, chloride, and nitrate : 

 they may be respectively formed by dissolving metallic 

 iron in dilute sulphuric, hydrochloric, or nitric acids, 

 evaporating and crystallising the solution as much as 

 possible out of contact with the atmosphere. 



116. Iron Solutions. Iron may be reduced from a 

 solution of its protosulphato (green copperas), made by 

 dissolving metallic iron in dilute sulphuric acid ; or from 

 its protochloride, which is preferable, and which is made 

 by dissolving iron in hydrochloric acid. We have de- 

 posited it in the state of regulino white metal, by passing 

 a current of considerable intensity (15 or 20 pairs) for 

 one hour, through an anode of iron immersed in a 

 saturated aqueous solution of sal-ammoniac ; its appear- 

 ance when deposited from this liquid is rather white, 

 and very similar to that of freshly broken cast-iron. By 

 the same means it may also be deposited, using a satu- 

 rated solution, either of carbonate of ammonia, acetate 

 of ammonia, or acetate of potash. Good metal may be 

 obtained from a saturated aqueous solution of a mixture 

 of two parts of protosulphato of iron and one part of sal- 

 ammoniac. We have deposited it from an aqueous solu- 

 tion of ferrate of potash, which may be formed either by 



igniting peroxide of iron (crocus) very strongly for some 

 minutes with caustic potash and saltpetre. Or make a 

 very strong solution of caustic potash, immerse it in a 

 large iron or steel anode, and a small copper or platina 

 cathode, and pass a strong current from fifteen or twenty 

 pairs of Sinee's batteries through it until it acquires a 

 deep amethyst or purple colour; by that time the 

 cathode will have obtained a coating of iron, which will 

 be in the state of a dark powder if the power have been 

 too great, or it will have the appearance of white cast- 

 iron, or intermediate between that and the appearance of 

 reguline deposited zinc, if the power have been sufficiently 

 weak. This solution rapidly decomposes without any 

 very apparent cause, becoming colourless, and depositing 

 all its metal in the state of peroxide at the bottom of 

 the vessel. Iron may be very easily deposited from its 

 sulphate, thus : Dissolve a little crystalline sulphate of 

 iron in water, and add a few drops of sulphuric acid to 

 the solution ; one pair of Smee's batteries may bo used 

 to deposit the irou upon copper or brass. The metal in 

 this pure state has a very bright and beautiful silvery 

 appearance. An aqueous solution of cyanide of potas- 

 sium is a very bad conductor with an iron anode, even if 

 it be maintained hot. 



117. Cobalt Solution. A solution of protochlorido of 

 cobalt may be easily formed by digesting commercial 

 brown oxide of cobalt in hot hydrochloric acid ; it is a 

 deep-blue liquid, but changes to a reddish-brown colour 

 on the addition of water ; by slow cooling, fine red crys- 

 tals of the chloride may be obtained. We have not tried 

 this liquid for electro-deposition. 



118. Nickel Solutions. The nitrate of nickel solution 

 may be formed by dissolving nickel in nitric acid 

 slightly diluted with water, and, when dissolved, diluting 

 with additional water; it is a solution which does not 

 yield its metal freely. We have deposited nickel in the 

 state of reguline white metal, from a solution of the 

 double chloride of nickel and ammonia, by making a 

 lump of metallic nickel the anode in a strong aqueous 

 solution of sal-ammoniac, and passing a strong current of 

 electricity through it for several hours, until the liquid 

 acquired a pale greenish-blue colour. Wo have also 

 obtained a similar deposit by treating a solution of one 

 part of arseniate of potash and five parts of water in a 

 similar manner. It has also been deposited from a solu- 

 tion formed by dissolving pure nickel in nitric acid, then 

 diluting and precipitating it by a solution of carbonate 

 of potash, or cyanide of potassium ; washing the pre- 

 cipitate, and dissolving it nearly to saturation, in a solu- 

 tion of cyanide of potassium, and operating upon this 

 liquid, by the battery process, with an anode of pure 

 metal. Its appearance, when deposited from this solu- 

 tion, is said to be nearly equal in whiteness to silver, 

 and its deposition has been proposed to be applied to 

 the production of an inferior class of plated articles. 



119. Copper Salts. The ordinary salts, '<bc., of copper, are 

 the protoxide (black oxide of copper), sulphate, cliloride, 

 nitrate, acetate, and cyanide. To make the protoxide, 

 heat either the carbonate or nitrate to a moderate red 

 heat, or the sulphate to intense redness. The sulphate 

 may bo formed by heating one equivalent (31 7 parts) of 

 copper filings, and at most two equivalents (98 parts) of 

 oil of vitriol, until the residue is quite dry ; then dis- 

 solving the product in water, filtering, evaporating, and 

 crystallising the solution.; but it is much more con- 

 venient to purchase it, on account of its low price. The 

 chloride and nitrate may be formed the first by dis- 

 solving copper in aqua regia, or by saturating hydrochloric 

 acid with protoxide of copper, and evaporating and crys- 

 tallising the liquids; and the second, by dissolving 

 copper in nitric acid, evaporating and crystallising the 

 solution. Acetate of copper is most conveniently pur- 

 chased ; its commercial name is crystallised verdigris. 

 Cyanide of copper may be made by adding a solution of 

 cyanide of potassium to a solution of sulphate of copper 

 (each liquid being cold), as long as a precipitate can bo 

 produced filtering and washing the precipitate, which is 

 the required compound ; it is a fine powder, of a pale- 

 green colour. In the operation, a large quantity of 



