METALLURGY. (Tin.) 



387 



crease in weight caused by substituting alu- 

 minum for copper. For high-tension cables, alu- 

 minum may possibly be in some cases cheaper 

 than copper. The author suggests that since the 

 cost of power required for the electrolytic conduc- 

 tion of aluminum is higher than that of any other 

 electrolytic manufacture, it will be advantageous 

 to use water-power. 



Mr. W. H. Preece has observed that when alu- 

 minum wires break, they give way at points 

 where impurities exist; and for that reason, he 

 remarks, it is satisfactory that the purity of the 

 metal has been increased by recent processes. 



It is shown by Prof. T. W. Richards that in 

 the classification of alloys of aluminum the use- 

 ful ones fall into two groups those in which 

 small amounts of another metal are present with 

 aluminum, and those in which aluminum is added 

 in small amounts to other metals. Generally 

 speaking, according to William Campbell and 

 John Mathews, the metal present in the smaller 

 amount should not exceed 15 per cent.; and in 

 alloys of the first class much smaller proportions 

 give the maximum improvement in the alloy, 

 hardness being one of the qualities most sought. 

 Aluminum seems to be able to take up consider- 

 able quantities of certain metals without under- 

 going change of volume, though the density and 

 probably the hardness are improved in such 

 cases. Aluminum seems to form intermetallic 

 compounds more readily than any other single 

 metal, unless it be the metals of the alkalies. 

 On the other hand, there are several metals with 

 which it will not combine or even mix to give 

 homogeneous alloys except when the added metal 

 is present in very small quantities. Among the 

 metals of this class, lead, bismuth, and cadmium 

 may be mentioned. 



Specimens of alloys of aluminum in the form 

 of wire 0.126 inch in diameter were placed by 

 Prof. E. Wilson on the roof of King's College, 

 London, where they remained about thirteen 

 months, in order to investigate the effect of ex- 

 posure to a London atmosphere. The percentage 

 of variation of specific resistance had a some- 

 what wide range, according to the conditions. 

 Corrosion increased with the percentage of cop- 

 per. Nickel alloyed with copper had the effect of 

 slightly increasing conductivity during exposure. 

 The conclusion was reached that copper alone 

 should not be used in light aluminum alloys. 

 The presence of equal amounts (about 1 per cent.) 

 of nickel and copper certainly reduced conductiv- 

 ity to a small extent, but the gain in mechanical 

 and non-corrosive properties was great. 



From tests made at the Zurich Polytechnic In- 

 stitute of aluminum bronzes furnished by the 

 Neuhausen Aluminum Company, it is found that 

 the specific gravity of the metal first rises and 

 then falls, as the percentage of aluminum in- 

 creases. The maximum strength for soft alloys 

 was obtained with 3.4 per cent, of aluminum, 

 and for hard alloys with 1.4 per cent, of that 

 metal. For brass, the elasticity decreases with 

 the increase of aluminum, and is extremely low 

 with 2 per cent, of it. Iron in the proportion in 

 which it is present in the alloys was not ob- 

 served to influence sensibly the physical charac- 

 teristics. Aluminum bronze containing 10 per 

 cent, of aluminum with 1.5 per cent, of silicon 

 and iron is too brittle to be of any practical 

 value. As regards abrasion by friction, the hard 

 alloys, with less than 89.6 per cent, of copper, 

 lose little in weight, while the soft alloys, with 

 less than 6 per cent, of aluminum, heat and wear 



rway rapidly. 

 The addition of a small quantity of aluminum 



has been found by E. S. Sperry advantageous in 

 the manufacture of German silver. It greatly 

 improves the qualities of the alloy, ca'using it to 

 fill the molds completely and entirely preventing 

 the formation of blow-holes. Less than 0.05 per 

 cent, of aluminum is required to impart this 

 quality. The addition of larger proportions, as 

 from 3 to 3.5 per cent., gives the metal qualities 

 that make it more like tempered steel than any 

 other of the non-corrosive alloys. Hard and stiff 

 bars can be worked and machined. As the best 

 formula for this hard alloy, Mr. Sperry gives: 

 Copper 57, nickel 20, zinc 20, and aluminum 3 to 

 3.5, according to the stiffness required. 



Tin. In the process of Paul Bergsoe for the 

 electrolytic recovery of tin from scrap and waste 

 alloys, the tin-bearing materials are reacted upon 

 by stannic chlorid, and the stannous salts formed 

 are subjected to electrolytic treatment. In the- 

 ory the process is identical with the Hoepfner 

 process for extracting copper, which depends 

 upon the varying valences of the metal. This 

 process consists in bringing a salt of copper in 

 a higher state of oxidation into contact with the 

 ore, whereupon copper passes into solution and 

 the solvent is reduced from the cupric to the 

 cuprous condition. This solution is then elec- 

 trolyzed with insoluble anodes, whereby it is 

 caused to deposit one-half of its metal, with res- 

 toration of its valence and solvent power and 

 recovery of an amount of metal equivalent to that 

 dissolved. The Hoepfner process has encountered 

 in practise the very serious obstacle of a low re- 

 action velocity a solvent action so slow as to 

 render its application to the most commonly oc- 

 curring ores of copper, the sulfids, of doubtful 

 practicability. From this defect the tin process 

 is free, for the stannic salts are energetic solvents. 

 The successful treatment of tin scrap, however, 

 has proved in the past a difficult problem, on ac- 

 count of its very low tin content and because 

 of the tendency of the iron to pass with the tin 

 into solution. The industrial value of the new 

 process as applied to this purpose is therefore 

 yet to be investigated. 



Two electrolytic processes for the recovery of 

 tin from tin -scrap as carried out in work in 

 Germany are described in an anonymous article 

 in the Zeitschrift fur Electrochimie, both of 

 which are based on the use of scrap as anode 

 material. In one the bath contains sodium chlo- 

 rid and hydrate; in the other, hydrochloric acid. 

 It is an advantage of the former method that less 

 iron gets into the solution; but, on the other 

 hand, the energy efficiency of the process is lower, 

 and when it is used, the deposit obtained at the 

 cathode is more spongy. The failure to get me- 

 tallic tin directly is a disadvantage of both proc- 

 esses. The metal can, however, according to the 

 article, be obtained in the electrolytic bath under 

 certain conditions. Pfenhauser has suggested 

 that avoidance of the formation of sponge may 

 be simply a question of maintaining the concen- 

 tration of the tin-salt solution near the cathode 

 a condition which appears to be difficult in 

 works treating tin-scrap on an industrial scale. 

 The problem of producing metallic tin at the 

 cathode is complicated fiirther by the slow, grad- 

 ual increase of impurities in the electrolyte. Of 

 several works that have been built in Germany 

 for carrying out the electrolytic process, the 

 largest is that of Goldschmidt at Essen, where 

 from 50 to 60 tons of tin-scrap are treated per 

 day. Other works have been or are being built 

 in Austria and Germany, and a company was 

 formed in England in 1901 to operate an elec- 

 trolytic works. 



