METALLURGY. 



463 



chalopyrite). bornite (or purple copper ore), copper 

 ghuiee'ior redruthitei. ami imli,u r <' cupper. The ores 

 first undergo calcination in heaps. " stalls," kilns. 

 or reverberatory furnaces, The first two methods 

 are >. >nu 'what wasteful, and arc adopted only where 

 timber is abundant. Kilns are generally used for 

 :'<x>r in sulphur. In the Swansea district (Wales) 

 reverberatory i'urnac-es are mostly used. The tem- 

 perature of the furnace is not raised so high that 

 the ore fuses. In calcination most of the arsenic 

 and part of the sulphur are converted into oxides 

 and carried off with the products of combustion. 

 The calcined ore now undergoes the " melting " or 

 "fusion" process after mixing with "metal slag." 

 The resulting product, known as "coarse metal,'' is 

 granulated by running into water. It should ap- 

 proximate the formula ('uFeS 3 . The granulated 

 metal is again roasted, and the iron sulphide is con- 

 verted into oxide. The " roasted coarse metal " is 

 now fused with refinery slags, so that the iron is 

 carried off in the slag as a silicate, and the copper 

 separates as " white " or " fine metal." This should 

 contain about 75 per cent, of copper and nearly 

 correspond to the formula Cu 2 S. It is then roasted, 

 by which process sufficient C'u s S is converted into 

 C'ugO, so that when melted they may react and form 

 Cu and S0 2 . On fusion the reaction takes place 

 with violent boiling. The crude copper is known 

 as " blister " or " pimple copper " from its appear- 

 ance, and it should contain about 95 per cent, of 

 copper. It is refined by melting and oxidation of 

 the impurities, and then "poling" to reduce the 

 copper which has been oxidized. As to the third 

 class of methods, burned pyrites from sulphuric-acid 

 works frequently contain small amounts of copper. 

 They are calcined with rock salt, by which means 

 copper chloride is produced. By scrap iron the 

 copper is precipitated from its solution. The crude 

 copper is purified as above or by electrolysis. Cer- 

 tain ores, on treatment with dilute sulphuric acid, 

 give up their copper as sulphate, which in its turn 

 may be treated with scrap iron. 



In a process applying electrolysis to the treat- 

 ment of low-grade copper ores, the finely ground 

 ore is leached with a hot solution of cupric chloride, 

 previously mixed with calcium solution, in a rotat- 

 ing barrel, through which a low voltage alternating 

 current is passed! The solution is then run through 

 a receptacle containing copper oxides or hydrates, 

 which remove iron and other impurities from it, 

 and is then conveyed into rectangular vats fitted 

 with asbestos diaphragms and electrodes. The cop- 

 per being deposited, the fluid is pumped back for 

 re-use. The resulting ore, being freed from copper 

 and chemically disintegrated, is said to be in an ex- 

 cellent condition for treatment by the cyanide or 

 other similar pr 



The Refractory Metals. Important additions 

 have been made within the past two or three years 

 to our knowledge of the refractory metals through 

 the researches of M. Moissan with the electric fur- 

 nace, in which he had the advantage, of higher 

 temperatures than it had previously been practica- 

 ble to attain. His success in the reduction of sev- 

 eral of these metals, including some of the most 

 difficult, was recorded in the " Annual Cyclopedia '' 

 for 1895. His experiments have been continued, 

 but chiefly with respect to the combinations of 

 those metals and the properties of their com pounds, 

 particularly of their carbides. Some of the results 

 of these experiments are of interest to the metal- 

 lurgist. 



The question of the fusibility of platinum in a 

 furnace fed with carbon and air has been compli- 

 cated by the possibility that metal which was so 

 fused might be contaminated by carbon or other 

 substances in the furnace. Victor 31 ever has, how- 



ever, recently melted platinum inclosed in a thiek 

 lilock of refractory earth under conditions in which 

 a ci rtainty existed that no impurities were prc.-ent. 

 At the same time an alloy of 25 per cent, iridium 

 and 75 per cent, platinum remained unattacked, 

 and kept its outer form and its luster quite un- 

 altered. 



A coal mine in the high plateau of the Andes, 

 about 16,000 feet above the sea, has been found to 

 be an important source of vanadium compounds. 

 The ash, constituting about 2 per cent, of the 

 product, contains from | to of its weight of 

 vanadium, besides some silver, with traces of zir- 

 conium and platinum. The vanadium has been ex- 

 tracted on a considerable scale by M. K. Helouis, 

 who has applied it to the preparation of aniline 

 black, to the coloring of porcelain, and in metal- 

 lurgy. 



In the reduction of vanadic acid with charcoal in 

 the electric furnace, M. Moissan has obtained easily 

 and in abundance a melting of vanadium titrating 

 from 4 to 5 per cent, of carbon. With a longer 

 continued heating, a new, definite, and crystallized 

 carburet is obtained. This compound does not act 

 upon water at the ordinary temperature, and is 

 more stable than melted vanadium in the presence of 

 acids. Pure vanadium unites at the temperature 

 of the electric furnace with iron, copper, and alum- 

 inum, but does not form an alloy with silver. 



The properties of molybdenum obtained from its 

 amalgam by distillation in a vacuum at a low tem- 

 perature are found by M. J. Feree to be different 

 from those of molybdenum as hitherto obtained. 

 The substance is pyrophoric, and ignites in the air, 

 yielding inolybdic oxides which are partially vola- 

 tilized by the heat liberated. It loses this property 

 if heated above 400 C. It becomes incandescent 

 in a current of sulphurous acid, which is entirely 

 absorbed, forming molybdenum sulphide and mo- 

 lybdic oxides. Nitrogen, carbonic acid, and hydro- 

 gen sulphide seem to have no action at the ordi- 

 nary temperature or at a gentle heat. Carbou mon- 

 oxide is rapidly decomposed. 



It results from the researches of M. Guichard on 

 molybdenite and the preparation of molybdenum 

 that it is easy to produce by the action of the elec- 

 tric arc a melting of molybdenum free from sul- 

 phur. This very simple preparation may. perhaps, 

 present some interest in connection with the manu- 

 facture of molybdenum steels, and also with the 

 use of the metal in the treatment of iron in the 

 Bessemer converter ; for M. Moissan has shown 

 that molybdenum has the advantage over man- 

 ganese of giving a volatile oxide, and of not sen- 

 sibly modifying the properties of iron. 



M. Moissan finds that rhodium, iridium. and pal- 

 ladium dissolve carbon with ease at the tempera- 

 ture of the electric furnace, and give it, on solidify- 

 ing, in the form of graphite. Xo combination to 

 form a carbide appears to take place. 



Pin-e tungsten is obtained by M. Moissan by the 

 reaction of tungstic acid with carbon in the electric 

 furnace. With a large excess of carbon the carbide 

 CWo is formed, which in the fused state readily 

 dissolves more carbon, graphite crystallizing out on 

 fusing. The pure metal can be 'readily filed and 

 forged, welds easily, has no action on the magnetic 

 needle, and has a melting point higher than that of 

 chromium or molybdenum. 



Alloys. It is "now quite usual, says Prof. W. ('. 

 Roberts-Austen, to think of alloys as being solid 

 solutions and to recognize that the atoms of solid 

 metals are in active movement. That this must lie 

 the case is revealed by the passage of metals to allo- 

 tropic modifications in which the physical proper- 

 ties differ widely from those of the same metals in 

 their normal state. The subject was first brought 



