METALLURGY. (COPPER, NICKEL, TIN, AND ZINC.) 



357 



I 



clnstries and Iron, the world's total output of 

 electrolytic copper fifteen or twenty years ago did 

 not exceed from 15 to 20 tons a week. In 1881 

 and 1882 this amount was increased by the erec- 

 tion of new refineries to about GO tons. In years 

 succeeding several American refineries began oper- 

 ation, and between 1888 and 1890 the world's 

 total production was between 280 and 300 tons per 

 week. Since that time a very large number of 

 refineries have come into existence in different 

 countries, and it is safe to estimate the world's 

 production at the present time as not less than 

 500 tons per day, or about 180,000 tons per annum. 

 Dining the refining of this quantity of metal not 

 less than 20,000,000 ounces of silver and 100,000 

 ounces of gold are recovered. Converted into a 

 money value, these weights represent $45,000,000 

 in copper, $12,500,000 in silver, and $2,000,000 in 

 gold. 



Of the physical properties of electro-deposited 

 copper, the same authority said, in a lecture before 

 the Institution of Electrical Engineers, that copper 

 prepared by electrolysis may have a density as 

 low as 8, while the density of normal copper is 8.9. 

 Hard rolling, cold hammering, and hard drawing 

 increase the tensile strength and limit the elas- 

 ticity of copper considerably. The extensibility 

 of annealed copper becomes less at high tempera- 

 tures, and that of mechanically worked copper 

 becomes higher. Some copper sheets (not an- 

 nealed) deposited by the electrolytic centrifugal 

 process, 0.0245 of an inch in thickness, broke at 

 433 pounds, which is equivalent to 22.1 tons per 

 square inch. Hani-drawn wire made by this pro- 

 cess has a tensile strength of 29 tons per square 

 inch, and annealed wire 20 tons, the electrical 

 conductivity being 99 per cent. 



Of the recent improvements in the production 

 of electrolytic copper, having in view both increase 

 of the deposit and smoothness and homogeneity, 

 rne of the earlier plans for increasing the output 

 was that introduced by Elmore, in which an agate 

 burnisher was caused to pass continuously over 

 the surface on which the deposit was being made. 

 A metal of very great strength was thereby ob- 

 tained. In a more recent development a sheepskin 

 impregnated with animal fat is vised as a bur- 

 nisher. In a method introduced by Mr. Sherrard 

 Cowper-Coles, the copper is deposited upon a ver- 

 tical mandrel, which is caused to rotate very 

 rapidly. The centrifugal force developed and the 

 \vash of the electrolyte over the rotating surface 

 keep it clean and free from gas, making a smooth 

 and dense deposit nearly certain. 



The physical tests of metallic nickel, as Mr. 

 David H. Browne shows in a paper on The Proper- 

 ties and Possible Uses of Nickel Steel, furnish 

 no explanation of its remarkable effects when al- 

 loyed with iron. The most notable of these effects 

 is the manner in which nickel increases the elastic 

 effects of the steel to which it has been added, 

 a fact exhibited in the much greater resistance 

 which the metal develops against numerous and 

 repeated strains; or, in other words, in the exten- 

 sion of the limit at which molecular fatigue begins 

 as distinguished from molecular distortion, which 

 is effected by the addition of the small percentage 

 of nickel. This is the property that emphatically 

 distinguishes nickel steel from simple steel. After 

 discussing the advantages of nickel steel for bridge 

 construction, for plates for boiler and tank work 

 and ships' hulls, armor plates, shaftings and for- 

 cings, Mr. Browne mentions as among the purposes 

 for which the alloys of that name are applied 

 resistance wire, bicycle tubing and spokes, stay- 

 holts, fire-box sheets, boiler tubing, firearms, safes, 

 and vaults, bobbin spindles, and a great variety 



of other purposes for which some peculiarity of 

 strength, ductility, or incorrodibility gives it 

 special fitness. One of the most promising of 

 these uses is the making of tool steel. For this 

 purpose the alloy containing about 0.80 per cent, 

 carbon with 3 per cent, of nickel is probably the 

 best for everyday use. Increasing the nickel to 

 5 or 6 per cent, increases the strength, but necessi- 

 tates skilled treatment in forging. Tool steel with 

 0.80 per cent, carbon and from 3 to 5 per cent, 

 nickel possesses all the properties of high carbon 

 simple steel without its brittleness. Nickel steel 

 shows very pronounced toughness. A nickel-steel 

 tool containing 4 or 5 per cent, of nickel with 

 0.80 per cent, carbon is as hard after tempering 

 as the best simple tool steel of from 1 to 1.25 per 

 cent, carbon without the brittleness and glassy 

 nature which distinguish the latter. When used 

 for drills the nickel steel appears to work with 

 much less than the usual friction, and does not 

 become so hot in use as carbon steel. Nickel steels 

 are exceedingly sensitive to heat treatment, but 

 are less easily spoiled by overheating, and may 

 therefore be worked at a somewhat higher tem- 

 perature than a carbon steel that will give the 

 same temper. 



A molecular transformation of tin organ pipes, 

 under which the metal crumbled to a gray powder, 

 was first noticed in 1851 by Erdmann. It was 

 observed again by Fritsche at St. Petersburg, and 

 has since been studied repeatedly by various ob- 

 servers. The matter has more recently been taken 

 up by Messrs. Cohen and Van Eijik, who in a 

 preliminary dilatometric study of a gray tin dis- 

 covered the existence of a transition temperature 

 at about 30 C. A transition element was there- 

 fore constructed, having gray tin as one electrode 

 and ordinary white tin as the other. A study 

 of the electro-motive force of this cell with vary- 

 ing temperatures showed that the reaction, gray 

 tin to white tin and white tin to gray tin, was a 

 reversible one, with a transition point at 20 C. 

 A careful determination of the same point by the 

 dilatometric method gave the same value. All 

 the observations of early workers are brought into 

 line by this research. The authors point out that, 

 except during a few warm days, all tin is in an 

 unstable equilibrium, and tends to transform itself 

 slowly into the gray powder modification. 



Three commercial methods for the extraction 

 of zinc are defined by Capt. C. C. Longridge in 

 a paper on that metal and its treatment. They 

 are the dry, or most usual process, by reduction, 

 distillation, and condensation, by which metallic 

 zinc is obtained; the chemical, a little-used meth- 

 od, which results in the formation of zinc com- 

 pounds from which the metal has to be won in 

 the dry way; and the electrolytic process, which 

 is more or less in an experimental stage. Not 

 only ores, but furnace and refinery products, fur- 

 nace or retort residues containing zinc ore, calcined 

 silver ores rich in zinc, and alloys of zinc with 

 lead, silver, and gold are treated by the dry pro- 

 cess. In many cases zinc extracted from ores or 

 by-products by the dry process is too impure. 

 Refining is accomplished by slow fusion at the 

 lowest possible temperature, the melted metals 

 being retained in this state for a considerable time, 

 while the lighter impurities rise as scum, the 

 heavier metals sink to the bottom, and the puri- 

 fied zinc forms a middle layer. This process has 

 been improved in this country by the utilization 

 of natural gas. 



The chemical or wet process is characterized by 

 the author as unsuitable and costly. Its use is 

 chiefly confined to separating zinc from valuable 

 alloys, etc., and converting it into marketable by- 



