METALS. 



543 



fine appearance, by plunging them in a solu- 

 tion of 10 grammes of chloride of iron in half a 

 litre of alcohol at 60 0., and in contact with 

 metallic zinc. 



New Processes for Covering Metals with an 

 Adherent and Brilliant Coating of other Metals. 

 The foregoing process may perhaps have been 

 suggested by those of M. Fred. Weil, described 

 in Le Technologiate, February, 1865, and also 

 in Annales de Chimie et de Physique, for the 

 same year (translated in Chem. News, January 

 5, 1866). In regard to these processes, Prof. 

 Miller, before the British Association in 1865, 

 remarked as follows : 



" An extensive branch of industry is now 

 springing up in the improved methods of vol- 

 taic deposition of the metals. Weil has, by 

 the use of an alkaline solution of tartrate of 

 copper, contrived to coat iron and steel 

 with a tough closely adherent sheathing of 

 copper, by simply suspending the articles to be 

 coated by means of a wire of zinc in the metal- 

 lic bath. No battery is required. Lead and 

 tin may in a similar manner be deposited on 

 copper, iron, or steel, if the oxide of tin or of 

 lead be dissolved in a bath of strong solution 

 of caustic soda." 



M. Weil employs baths of salts or oxides of 

 the metals, held in alkaline solution (sodic or 

 potassic), either, as more commonly, by means 

 of inoffensive organic matters which tend to 

 prevent precipitation of oxide by the fixed 

 alkali, such as tartaric acid, glycerine, albumen, 

 etc., or by the excess of the fixed alkali itself; 

 and the deposit is secured, according to differ- 

 ence of the cases, either with or without the 

 cooperation and contact of metallic zinc or 

 lead, and at ordinary temperatures or those less 

 or more elevated. 



The most usual coatings, and generally speak- 

 ing the most valuable, are those of copper and 

 of bronze, and particularly as applied upon 

 iron, cast-iron, and steel. The metals to be 

 operated on do not require a previous coating 

 of foreign conducting matters, as black lead; 

 but they are to be thoroughly cleansed with 

 water acidulated with sulphuric acid to 2 B, 

 the action being continued from 5 to 20 min- 

 utes, then washed in plain water, and finished 

 in water made alkaline with soda ; then 

 cleaned with a scratch-brush, again washed, 

 and plunged into the copper bath in contact 

 with zinc. For this purpose, it is more econom- 

 ical to suspend simply wfth zinc wire than to 

 use zinc plates ; and the time of immersion 

 may vary, according to the effect sought, from 

 3 to 72 hours. 



A copper solution giving very satisfactory re- 

 sults is formed by dissolving in 10 litres of 'water 

 350 grammes of crystallized sulphate of copper, 

 1,500 do. of sodio-potassic tartrate, and 80 do. 

 of soda lime, containing from 50 to 60 per cent, 

 of free soda. The solution does not attack 

 iron, cast -iron, or steel, or other metals whoso 

 oxides are insoluble in potash and soda. Care 

 is to be taken that the iron or other articles 



to be coppered do not touch each other. The 

 coating of copper increases within certain 

 limits with the duration of the immersion, and 

 it adheres firmly; but when it is necessary to 

 fit this for resisting alternations of moisture and 

 dryness or the action of sea-water, additional 

 thickness must be given by employment of a 

 battery, either with an acidulated copper solu- 

 tion or with the special solutions above indicated. 

 In cases in which such additional thickness is 

 not necessary, after sufficiently long immersion 

 in the bath, the liquid is drawn off through a 

 tap, and the coppered articles are washed in 

 water, then cleaned with a scratch-brush, and 

 dried, first in sawdust and then in a stove. 



When, after a great number of copperings, 

 the liquids become exhausted, they may be re- 

 newed by precipitating the zinc in solution by 

 sulphide of sodium, not in excess, and recharg- 

 ing the solution with sulphate of copper. The 

 incidental ingredients, such as soda, sodio- 

 potassic tartrate, glycerine, etc., serve for an 

 indefinite time. In the second of the accounts 

 above referred to, methods are indicated for 

 keeping the copper solution saturated, or of 

 a given strength, throughout operations con- 

 ducted on a large scale. 



The advantages claimed by the author for 

 his process are : 1, the perfect adherence of the 

 copper deposited on iron, cast-iron, and steel ; 

 2, rapidity, simplicity, and economy ; 3, faith- 

 ful reproduction in the coating of the most 

 delicate details; 4, beauty of the colors and 

 tones secured by deposits of different materials 

 or under different conditions; 5, harmlessness 

 and stability of the solution; 6, the power of 

 repairing a damaged copper or other coating 

 secured by these processes. 



Yellow bronzes in copper baths bronze in 

 beautiful tints, and without contact with zinc. 

 The finest tints were furnished by an alloy of 

 copper, 83 ; zinc, 14 ; lead, 0.6 ; tin, 1 .3 ; nickel, 

 1.1. Iron and other metals immersed in con- 

 tact with zinc in a copper bath to which is 

 added some stanuate of soda, or solution of 

 bichloride of tin with soda, are covered with a 

 true bronze (coating of alloy of copper and tin). 

 The zincing of copper or coppered articles is 

 speedily effected by immersing them in a con- 

 centrated solution of caustic potash or soda, 

 heated to nearly or quite 100C. ; and in a 

 longer time, when the solution is cold. By 

 adding to such solution a salt of tin or of lead, 

 and heating to from 50 to 100C., the articles 

 just named, as well as iron, cast-iron, and 

 steel, can (in contact with zinc) be tinned or 

 leaded ; though the deposit will contain some 

 zinc. To secure a deposit of tin, pure, and 

 of increasing thickness, place in a vessel con- 

 taining the tin solution a porous vase hold- 

 ing the alkaline lixivium and the metallic 

 zinc; and then, plunging the article to be 

 tinned into the outer vessel, connect it by 

 a conducting wire with the zinc. In tartro- 

 alkaline baths containing cobalt or nickel in- 

 stead of copper, and heated, articles in the last- 



