ooi-PEE DEPOSITION.] UNDULATORY FORCES. ELECTRO-METALLURGY. 



233 



kept in constant motion, gently swinging to and fro the 

 metal frame upon which they are suspended having four 

 small wheels running upon four small inclined planes 

 fixed upon the edges of the vat, which are kept in 

 constant motion by steam or other available power. 



199. Temperature of Solution. Several solutions, such 

 as the cyanide of copper and potassium, the cyanide of 

 gold and potassium, itc., require to be kept hot, in order 

 to make them conduct freely, and yield suitable metal ; 

 not that they cannot be worked cold, but that they work 

 much better and quicker at a high temperature, which 

 more than compensates for the expense of heating them. 



200. Protection of Depositing Liquids from Light. 

 Some liquids, such as the double sulphite of silver and 

 potash, and the hyposulpliite of silver and potash, require 

 to be protected as much as possible from the influence of 

 light ; and even the ordinary cyanide of silver liquid is 

 better screened from an excess of this agent. 



201. Clean Connections necessary. Tn every case we 

 must be very careful to observe that the circuit is 

 complete, and that it is capable of conducting the current 

 freely throughout ; that the articles to be coated are 

 conductors of electricity, or have been made so by any 

 of the means already recommended ; and that their 

 surfaces, as well as all the ends of the wires, at their 

 various points of contact, are perfectly clean. 



202. Management of Coppering Liquids. With the 

 sulphate of copper solution (120) no particular manage- 

 ment is required, beyond the general rules already laid 

 (lu.vn (19G). It is not suitable for depositing direct upon 

 zinc, tin, lead, iron, or steeL Articles formed of these 

 metal* ore first coated with a thin layer of copper, in the 

 cyanide of copper and potassium solution (120) ; then well 

 washed, and transferred immediately to the sulphate 

 solution, and tho remainder of the required thickness of 

 copper deposited upon it. 



203. Uset of Copper De/>ontion. Among the many 

 uses to which the electro-deposition of copper lias been 

 applied, we may mention the following : To make copper 

 cells for Daniell's batteries ; making copies of stereotype 

 plates, engraved copper plates, and engraved rollers ; 

 coppering the surface of printing- type ; coppering steel 

 pens (patented); to protect iron and steel goods from 

 rusting, coating telegraph wires, ship's bolts, <fcc. ; to 

 make copies of Daguerreotype pictures* ; to moke coppered 

 cloth ; to coat glass chemical vessels ; to coat and protect 

 metal and plaster statues, busts, and sculptured works ; 

 to preserve tho form of flowers, fruits, ferns, seaweed, 

 insects, reptiles, <tc. ; to make medallions, busts, and 

 various figures and ornaments in copper ; it has also been 

 applied in the arts of glyphography and electro-tint 

 printing. 



204. Making Objects in Copper, Coppering, Jcc. To 

 make a cell of Donicll's battery in copper, coat the inside 

 of a glass jar or earthen jolly-pot with wax, resin, or 

 stearine, by making the vessel hot ; then either blacklead 

 it thoroughly, or treat it with the phosphorus, silver, 

 and gold solutions ; or, what is more simple, coat it 

 uniformly all over the inside with tho phosphorus 

 moulding composition (87), and then treat it with the 

 gold and silver liquids. Make a connection by a fine 

 copper wire with the lower part of the coating ; fill tho 

 vessel nearly full of the sulphate of copper depositing 

 solution (120), suspend in it a sheet of copper, and 

 connect the sheet of copper and the tine copper wire with 

 a small battery of one or two pairs. If, instead of the 

 battery process, we adopt the single cell arrangement, 

 containing dilute sulphuric acid and a piece of zinc, 

 placing a porous cell in the sulphate solution, and con- 

 necting tho fine copper wire with the piece of zinc ; a 

 deposit of copper will soon spread over the entire inside 

 surface of the jar, when that has been previously prepared 

 by tho phosphorus method. Engraved steel plates are 

 copied by stopping-oil' tho back with copal varnish, 

 allowing it to bucomo perfectly dry. They are then im- 

 mersed in the cyanide coppering liquid, and a thin film 

 of copper is thrown down : after. washing well, they are at 

 once immersed in the sulphate of copper solution, and 

 the required thickness of copper is deposited ; this will 



VOL. I. 



] require from 24 to 48 hours. The surface of the steel 

 should be previously prepared for a non-adhesive de- 

 posit, otherwise the two metals cannot be separated. 



205. Copying Wood-cuts in Copper. For printing 

 purposes, where a large number of impressions of a par 

 ticular wood-cut is required, the plan of taking copies of 

 the engraved wooden block in copper by the electro- 

 process, and using those copies instead of tho original 

 block to print from, has been gradually extending itself 

 for some years, and has now attained a considerable 

 degree of importance; the vignette at tho head of the 

 title-page of the Illustrated News, the title-page of Punch, 

 many of the large engravings in the Illustrated News, and 

 even the illustrations of some of the penny periodicals, 

 are regularly produced in this way. To copy an engraved 

 wooden block, the engraved surface is first moistened with 

 water, and firmly enclosed by a shallow frame ; a thick 

 piece of gutta-percha, more than sufficient to fill the 

 enclosed space, and made quite soft by heat, is then laid 

 upon it, commencing its contact at the centre of the 

 engraving, and proceeding outwards, so as to exclude all 

 air-bubbles ; a plate of cold iron is then laid upon the 

 gutta-percha, and the whole subjected to pressure, gentle 

 at first, but increased to a high degree as tho substance 

 cools. The block and copy are then separated, and the 

 figured surface of the gutta-percha (with connecting 

 and guiding-wires previously attached) is treated in the 

 usual manner with blacklead or with the phosphorus, 

 silver, and gold solutions ; copper is then deposited upon 

 it in a solution of sulphate of copper, until a moderate 

 thickness of deposit is obtained, which will occupy at 

 least twelve or eighteen hours ; when sufficiently thick 

 the deposit is removed, its back made rigid by a layer of 

 solder or type-metal (the surface being previously 

 moistened with a solution of chloride of zinc to make the 

 solder adhere), the back is planed flat, and mounted 

 upon a block of wood to the height of tho type. In 

 London this process is carried on upon a large scale, some 

 of the copies being upwards of two feet square. En- 

 gravings upon steel are copied in an exactly similar 

 manner to those upon wood. 



We have recently tried some experiments with a view 

 of making the deposit of copper upon gutta-percha and 

 marine glue spread more rapidly than it does, by pre- 

 paring the surface with blacklead ; it being a matter of 

 some importance, in copying wood engravings for perio- 

 dicals of such large circulation as the Illustrated News, 

 that tho time occupied in the process be reduced. Our 

 experiments have succeeded to some extent, and wo give 

 tho following results of them for tho benefit of the 

 printing trade. 



After having formed a reverse copy, in gutta-percha 

 and marine glue, of the engraved wooden block, and 

 affixed the conducting wires to it, take a mixture of one 

 measure of spirit varnish, and either four or five mea- 

 sures of vegetable naphtha, and apply it very sparingly in 

 a thin layer, by a soft camel's-hair brush, over the whole 

 surface of the mould where the deposit is desired to be 

 spread. Whilst tho surface is still wot, cover it with a 

 mixture of three parts of yellow and one part of white 

 bronze powder, and bring the powder in thorough con- 

 tact with the whole of the moistened surface, by striking 

 it all over with a dry, soft brush ; then gently brush oil' 

 all the superfluous powder. Tho bronzed mould may 

 now be immersed in the ordinary sulphate of copper 

 solution, and the following actions will occur: The 

 particles of white bronze powder being composed almost 

 wholly of tin, and those of yellow bronze containing 

 much copper, those of tin will dissolve and coat them- 

 selves with copper by the simple immersion process (4), 

 and those of brass or copper (the yellow ones) will 

 become coated by their contact with those of tin (Two 

 Metals and One Liquid Process, 7), and thus a thin 

 deposit of copper will almost instantaneously spread all 

 over the bronzed surface. This effect will of course take 

 place without connecting the mould with the battery; 

 but they may be immediately connected together, and a 

 deposit will spread almost instantaneously over the whole 

 of the bronzed surface by the ordinary battery process, 



2 ii 



