532 



METALS. 



base. Such solutions are obtained from suphuretted 

 copper-ores, which have been calcined with common 

 salt, as in the Longraaid or Henderson process, or 

 when similar ores after roasting are digested with 

 chlorides of iron or other chlorides, as, for example, 

 in the Hunt and Douglas patent process. In case, 

 however, the solutions of copper to be precipitated 

 contain no chlorides, a portion of common salt is 

 added, and in case they contain no sulphates, a 

 portion of sulphate of soda or other soluble sul- 

 phate is added. In either case, these salts may 

 equal the amount of copper present. Such solutions, 

 containing both chlorides and sulphates, especially 

 if heated, as is usual in copper precipitation, very 

 quickly dissolve the tin from tinned iron when this 

 is immersed therein, and at once let it fall again as 

 an insoluble hydrated oxide of tin, which may be 

 readily drawn off while suspended in the liquid, and 

 collected by subsidence in proper tanks, to be sub- 

 sequently treated by methods known to chemists, 

 such as dissolving in hydrochloric acid and precipi- 

 tating by metallic zinc, by reduction in the dry way, 

 or by conversion into stannate of soda. The scrap- 

 iron thus freed from tin is then employed in the or- 

 dinary way to precipitate the dissolved copper, as 

 metallic or cement' copper^ from the solutions de- 

 scribed. The copper solution, holding the suspend- 

 ed oxide of tin, may be drawn off at once from the 

 iron to the settling-tank, and a fresh solution added ; 

 or the precipitation of the copper may be carried on 

 without interruption in the first solution till this is 

 exhausted, and the oxide of tin afterward separated 

 from the metallic copper by taking advantage of the 

 greater lightness and the more finely-divided state 

 of the former. Should it be desirable to remove the 

 tin from the iron plate without causing an immedi- 

 ate precipitation of copper thereon, this may be 

 effected by mixing a solution of perchlpridej or 

 other persalt of iron, with the copper solution. 



New Method of welding Copper. Improve- 

 ments m the operation of welding copper have 

 been introduced by a Baltimore firm (Messrs. 

 Rehbein, Eoberts & Brocchus). The two 

 pieces of copper to be united having previ- 

 ously been prepared, so that the surfaces form 

 a lap or other suitable joint, prepared borax 

 (biborate of soda) is applied on and between 

 the surfaces of the joint, which are heated and 

 hammered. The borax is prepared by being 

 heated until all the water of crystallization has 

 evaporated, when the residuum is pulverized 

 for use. After being hammered while hot, the 

 joint is further heated to a white heat, and 

 sprinkled over with a chloride, magnesic, sodic 

 (common salt), or other equivalent compound, 

 suitable for the exclusion of the oxygen, and 

 then finally welded, or during the welding 

 operation a stream of chlorine gas may be 

 directed upon the heated copper joint. 



Purification of Lead ~by Steam. This pro- 

 cess, as described in Iron, serves as a substi- 

 stute for stirring the molten lead either by 

 hand or by steam-machinery. The apparatus 

 employed in the steam system consists of an 

 upper and lower boiler, each with its own fur- 

 nace : the former, for the melting of the lead 

 and separating the silver, will contain about 

 nine or ten tons; and the lower, which is for 

 the crystallization, from fifteen to sixteen tons. 

 A stage, erected around the lower boiler, al- 

 lows the workmen to watch the operation and 

 remove the oxides. The metal. is run from the 



upper to the lower vessel through tubes fitted 

 with friction-valves moved by means of a lever ; 

 and in order to prevent the lead from pene- 

 trating into the steamway-pipe a valve-cock is 

 adopted. 



The lead, having been melted in the upper 

 boiler, is skimmed and run off into the lower 

 one, and at that moment a small jet of steam is 

 let in to effect the mixture of the crystals of 

 the previous operation with the lead in fusion. 

 A small stream of water, thrown upon the 

 surface of the lead at the commencement of 

 the operation, facilitates the formation of the 

 crystals. The steam is introduced from a boiler 

 close at hand, under the pressure of three at- 

 mospheres, through a lateral tube near the 

 bottom of the lower boiler, and is distributed 

 uniformly by means of a horizontal disk of 

 cast-iron placed over the nozzle of the steam- 

 pipe in the centre of the lower part of the 

 boiler. The boiler is fitted with a cover in 

 segments, which are opened alternately every 

 five or six minutes, when a workman detaches 

 such lead as has been flung by the action of the 

 escaping steam against the upper sides of the 

 boiler and adhered there. Beneath the lower 

 boiler are two small supplementary furnaces, 

 which bring up the discharge-tubes to the 

 proper temperature, and are lighted just pre- 

 vious to the drawing off. The steam causes a 

 violent and continued boiling of the whole 

 mass of metal in fusion most favorable to the 

 separation of the silver from'the lead and the 

 purification of the latter. The above action is 

 chiefly mechanical, but a sensible chemical 

 effect is also perceived, for the lead undergoes 

 a refining action independent of that which 

 results from its fusion at a dull-red heat pre- 

 vious to crystallization, so much so that all pre- 

 vious refining is dispensed with in the case of 

 moderately hard lead, though not when the 

 metal is very hard. 



If the chemical action of the steam were nil 

 the purity of the lead produced without pre- 

 vious refining could only be attributed to the 

 series of partial refinings to which the lead is 

 submitted by the fact of a great number of re- 

 meltings at a dull-red heat ; but a fact which 

 tends to show that the steam exercises a chemi- 

 cal action is, that the oxides which are produced 

 are first yellowish and earthy, but, as the op- 

 eration proceeds, become black and heavily 

 charged with copper, a circumstance which is 

 not produced in the boilers of the ordinary 

 system in spite of the most vigorous stirring. 

 Toward the end of the operation, while the 

 steam is still in action, in the liquid portion in 

 which are concentrated the silver, copper, anti- 

 mony, and arsenic, the lead is found to have 

 been deprived of the copper which it contained. 

 The antimony is gradually eliminated by the oxi- 

 dation caused by the air during the rerneltings ; 

 soft lead gives even more oxide than hard lead 

 containing more antimony, which proves that 

 the latter oxidizes first and preserves the lead 

 from oxidation. 



