938 COPPER 



descent coko absorbing all the oxygen, the iron is prevented from oxidising, and it 

 remains in a metallic state combined with some carbon. When this process is com- 

 pleted, the powder is drawn off into close vessels and kept until required for use, 

 carefully guarded from the air. If this preparation is thrown into a solution of 

 sulphate of copper, there is a violent action, and the copper in a metallic state is at 

 once thrown down. In practice, M. Bischoff prefers spreading out this preparation 

 in thin layers, and passing the copper water through it. The process has been in 

 use at some of the works on the banks of the Dee, and, as we understand, considerable 

 success has attended its use. The only difficulty appears to be in preserving the finely- 

 divided metallic iron from oxidation, which is essentially necessary to the success of 

 the process. 



Mr. S. Higgs junr. has greatly accelerated the process of precipitation by forcing 

 Bteam through the solution of copper in which pieces of iron have been placed. This 

 process has been successfully applied by him at Huel Margery copper-mine, St. Ives, 

 Cornwall. 



ALLOTS OF COPPER. Copper forms the basis of a greater number of important 

 alloys than any other metal. "With zinc it forms brass in all its varieties. See BRASS. 



Bronze and bell-metal are alloys of copper and tin. This compound is prepared in 

 crucibles when only small quantities are required ; but in reverberatory hearths, when 

 statues, bells, or cannons are to be cast. The metals must be protected as much as 

 possible during their combination from contact of air by a layer of pounded charcoal, 

 otherwise two evils would result ; waste of the copper by combustion, and a rapid 

 oxidation of the tin, so as to change the proportions and alter the properties of the 

 alloy. The fused materials ought to be well mixed by stirring, to give uniformity to 

 the compound. See BELL-METAL ; BRONZE. 



By an analysis of M. Berthier, the bells of the pendules, or ornamental clocks, 

 made in Paris, are found to be composed of copper 72'00, tin 26-56, iron 1'44 per cent. 



An alloy of 100 of copper and 14 of tin is said by M. Dussaussy to furnish tools, 

 which, hardened and sharpened in the manner of the ancients, afford an edge nearly 

 equal to that of steel (?). 



Cymbals, gongs, and the tam-tams of the Chinese are made of an alloy of 100 of 

 copper witB about 25 of tin. To give this compound the sonorous property in the 

 highest degree, it must be subjected to sudden refrigeration. M. D'Arcet, to whom 

 this discovery is due, recommends to ignite the piece after it is cast, and to plunge it 

 immediately into cold water. The sudden cooling gives the particles of the alloy 

 such a disposition that, with a regulated pressure by skilful hammering, they may bo 

 made to slide over each other, and remain permanently in their new position. When 

 by this means the instrument has received its intended form, it is to be heated and 

 allowed to cool slowly in the air. The particles now take a different arrangement 

 from what they would have done by sudden refrigeration ; for, instead of being ductile, 

 they possess such an elasticity, that, on being displaced by a slight compression, they 

 return to their primary position after a series of extremely rapid vibrations ; whence 

 a very powerful sound is emitted. Bronze, bell-metal, and probably all other alloys 

 of tin with copper, present the same peculiarities. 



Some valuable researches on alloys of copper and tin have recently been made by 

 M. Alfred Riche (Annalcs de Chimie et de Physique, xxx. [4], 1873, p. 351). It has 

 been asserted that the Chinese wtfrk their bronze at a red heat, but M. Riche lias 

 succeeded in making tam-tams by manipulating his bronze at much lower tempera- 

 tures. 



The bronze-founder should study to obtain a rapid fusion, in order to avoid the 

 causes of waste indicated above. Reverberatory furnaces have been long adopted for 

 this operation ; and among these, the elliptical are the best. The furnaces with 

 Bphoroidal domes are used by the bell-founders, because, their alloy being more fusible, 

 a more moderate heat is required ; however, as the rapidity of the process is alwaj-s 

 a matter of consequence, they also would find advantage in employing the elliptical 

 hearths. Coal is now universally preferred for fuel. 



The process of coating copper with tin exemplifies the strong affinity between the 

 two metals. The copper surface to bo tinned is first cleaned with a smooth sand- 

 stone ; it is then heated and rubbed over with a little sal-ammoniac, till it be perfectly 

 clean and bright ; the tin, along with some pounded resin, is now placed ou the copper, 

 which is made so hot as to melt the tin, and allow of its being spread over the surface 

 with a dossil or pad of tow. The layer thus fixed on the copper is exceedingly thin. 

 Bayen found that a copper pan, 9 inches in diameter and 3 inches deep, being 

 weighed immediately before and after tinning, became only 21 grains heavier. Now 

 as the area tinned, including the bottom, amounted to 155 square inches, 1 grain of 

 tin had been spread over nearly 7i square inches ; or only 20 grains over every sq. foot. 



Copper and Arsenic form a white-coloured alloy, sometimes used for the scales of 



