528 



METALLURGY. (ALUMINUM, COPPER, TIN.) 



Aluminum. Among the applications men- 

 tioned by Prof. W. P. Blake as having been made 

 of aluminum in the construction of portable in- 

 struments of precision are sextants made in New- 

 York, which have so far proved satisfactory ; a 

 mining transit made in Washington ; and a 

 double reflecting and repeating circle made in 

 New York for use on a boat and to be held in 

 the hand, weighing, exclusive of the eyepieces 

 and the handle, only one pound, or about one 

 third as much as an ordinary sextant. The 

 circle is about 9 inches in diameter and cast in 

 one piece. The casting is homogeneous and free 

 from blow holes, and dresses up clean and sharp. 

 The metal works well under the file, in the lathe, 

 and under the graduating tool. Every part has 

 also the requisite rigidity under the touch. The 

 drawbacks to the use of aluminum are that by 

 reason of its soft and " spongy " character it is 

 apt to tear under the tool, and that it does not 

 give clean threads. The former difficulty is 

 remedied by adding a small quantity of silver, 

 which increases the hardness considerably ; the 

 latter by a careful use of the tap and die. 



The Maussier aluminum process, which is being 

 introduced in Prance, comprises three stages 

 desilification, reduction, and liquation. Desilifi- 

 cation is effaced by fluorine or fluoride of calcium 

 in the presence of carbon, at a high temperature. 

 Lime, or carbonate of sodium or potassium, may 

 be added to facilitate the process. Reduction is 

 obtained by means of iron and manganese heat- 

 ed to incandescence in the presence of carbon. 

 Liquation, or separation of the aluminum from 

 the iron and manganese, is obtained by dropping 

 the molten mass into carbon ingot molds. 



In the electrolytic process of W. Diehl, of Ber- 

 lin, a bath is prepared of the fluorides of alkali 

 metals, or the compound fluorides of the alkali 

 metals and anhydrous alum, a sulphate of an al- 

 kali, and chloride of sodium. The substances are 

 melted together, allowed to cool down, ground, 

 and washed in water for removal of traces of 

 sulphur. The fluoride thus formed will consist 

 of aluminum fluoride and an alkaline fluoride. 

 It is melted with an alkaline chloride and fluor- 

 spar, and while in a molten state the mass is sub- 

 mitted to the electric current, when aluminum 

 is collected at the negative pole, and chlorine is 

 liberated at the positive pole. The alkaline flu- 

 oride which is formed may be melted with anhy- 

 drous alum or with a solution of nitrate of alumi- 

 num to form another double fluoride to which 

 electrolysis may be applied. 



In Dr. Netto's process, which has been at work 

 on the Tyne, cryolite is fused with salt, and so- 

 dium is added to the resultant product, when 

 sodium fluoride and metallic aluminum are ob- 

 tained. The sodium used in this process is ob- 

 tained by a method allowing melted caustic 

 soda to flow gradually into charcoal contained 

 in a cast-iron retort heated to dull redness 

 which requires a less high temperature than is 

 necessary in the Castner process. 



Graham's method is based upon the reduction, 

 by sodium, of fluoride of aluminum. The latter 

 substance is produced by the action of sulphate 

 of alumina on fluor-spar and cryolite ; but the 

 cryolite need be used only at the beginning of 

 the operation, for it is reproduced afterward as 

 a consequence of the reduction of the fluoride of 



aluminum. Under these conditions it is purer 

 than the natural mineral. 



Alfred E. Hunt, James W. Longley, and 

 Charles M. Hall have been studying the effects 

 of impurities on aluminum with the following 

 results: At very high temperatures aluminum 

 and sulphur combine to form a sulphide of the 

 composition A1 2 S 3 . Ordinary aluminum of com- 

 merce is free from sulphur. 'Lead is found as an 

 accidental impurity in aluminum in proportions 

 up to one quarter of 1 per cent. In small pro- 

 portions it appears to have no appreciable action 

 on the properties of the metal. In larger pro- 

 portions lead does not alloy with aluminum, and 

 no homogeneous alloy, or even mixture of the 

 metals can be obtained. Antimony does not 

 unite with aluminum to form any homogeneous 

 alloy. Chromium unites with it readily, harden- 

 ing it, and adds to its tensile strength. Tungsten 

 unites with it, hardening it, but not giving any 

 useful alloys. Platinum unites with it readily, 

 but the alloys are brittle and unsound. Accord- 

 ing to Fissier, silver seems to be the most useful 

 metal to improve aluminum. No very valuable 

 alloys of tin and aluminum have been discovered. 

 Tin'added to aluminum makes it more brittle, 

 and does not seem to give any useful properties in 

 return ; but small proportions of aluminum add- 

 ed to tin make it more elastic, without materially 

 decreasing its malleability. Cadmium unites 

 readily with aluminum, giving fusible alloys 

 which are malleable; but it seems to impart 

 weakness rather than strength. Bismuth forms 

 with aluminum brittle, but very fusible alloys. 

 ' Nickel unites with it, in any large proportions, 

 to form brittle alloys ; in small proportions, up 

 to 3 per cent, of nickel, the effect is to harden 

 aluminum without seriously decreasing its mal- 

 leability or ductility. Zinc readily forms alloys 

 with aluminum, which are brittle and highly 

 crystalline. The best solder yet obtained for 

 aluminum is the alloy of zinc with it, using 

 Venetian turpentine as a flux. Unfortunately 

 it will not flow well, and the soldered surfaces 

 are not capable of withstanding hard usage. 



Copper and Tin. As described by M. L. de 

 Launy, three methods of treating cupriferous 

 pyrites are pursued in the district of Huelva; 

 those of natural cementation, artificial cementa- 

 tion, and artificial cementation with chlorides. 

 The first of these methods is essentially one of 

 atmospheric oxidation. The broken ore is spread 

 out on floors in heaps varying from fifteen feet 

 to forty feet in thickness. Water is distributed 

 over the surface of the heaps, and the operation 

 is continued for several years. Three million 

 tons of ore are under treatment at a time. The 

 sulphates formed by the joint action of air and 

 water are dissolved in the water, and are col- 

 lected in channels leading to the cementation 

 tanks. These are filled with pig iron piled 

 checker-wise, through which the coppery liquors 

 are run in such a manner as to obtain the most 

 complete precipitation with a minimum consump- 

 tion of pig iron. The precipitated copper depos- 

 its on the surface of the pigs, and is cleaned off 

 about once a month. The term artificial ce- 

 mentation is applied to the method in which the 

 pyrites is burned in heaps previous to extraction 

 by water and precipitation. In the process of 

 artificial cementation with chlorides the copper 



