524 



METALLURGY. 



given only to the rich ore. The furnaces in 

 which the poor ore is treated are thirteen feet 

 high and three feet three inches in diameter. 

 Each furnace is closed at the top by a hopper 

 with two doors, the upper of which has a 

 water-joint. Twelve charges v are made each 

 day, and care is taken to open the upper door 

 as little as possible. The charge consists of 

 two hundred-weight of ore, mixed with a 

 quarter the quantity of charcoal. It is low- 

 ered into the furnace by opening the lower 

 door, while the upper door is closed; and a 

 fire is kept burning at the upper part of the 

 furnace to prevent the escape of the gases. 

 The mercurial vapors and gases of combustion 

 are led by a chimney into condensing cham- 

 bers. From 150 to 160 tons of ore are ex- 

 tracted at the Siele mines every month about 

 22 tons of metallic quicksilver ; and this is 

 packed in about 300 cans with screw stoppers. 

 Aluminum. The only establishment at which 

 aluminum is regularly manufactured is at Sa- 

 lindres, where about 2,400 kilometres are pro- 

 duced annually. The metal is prepared by 

 melting the double chloride of aluminum and 

 sodium with sodium and some cryolite as a 

 flux. The new method of obtaining the metal 

 from bauxite, proposed by Mr. Webster, does 

 not promise to be as successful in cheapening 

 its cost as its author hoped it would be. Mr. 

 "Webster has suggested a process of preparation 

 of alumina, for the purpose of manufacturing 

 aluminum, by heating alum with coal-pitch ; 

 subjecting the resultant mass, broken to pieces, 

 to the action of hydrochloric acid, for the 

 elimination of sulphureted hydrogen; adding 

 5 per cent, of charcoal-powder or lamp-black, 

 with enough water to make a thick mass; dry- 

 ing the mass made up into balls, and heating 

 the balls to a red heat for three hours under 

 exposure to air and the vapor of water, for the 

 conversion of sulphur and carbon into sulphur 

 dioxide and carbon dioxide, and the removal 

 of impurities. The dry residue, which con- 

 sists of aluminum oxide and potassium sul- 

 phate, is cooled and ground to a fine powder. 

 The powder is then treated with about seven 

 times its weight of water and boiled for about 

 an hour. The solution containing potassium 

 sulphate is then run off and evaporated to 

 dryne^s, and the alumina is washed out and 

 dried. Mr. J. Morris, of Uddington, near Glas- 

 gow, claims to obtain aluminum by treating 

 an intimate mixture of alumina and char- 

 coal with carbon dioxide. For this purpose 

 a solution of aluminum chloride is mixed with 

 powdered wood, charcoal, and lamp-black, and 

 then evaporated, until it forms a viscous mass, 

 which is shaped into balls. During the evapo- 

 ration hydrochloric acid is given off. The resi- 

 due consists of alumina intimately mixed with 

 charcoal. The balls are dried, and then heated 

 with steam in appropriate vessels for the pur- 

 pose of driving off all the chlorine, care being 

 taken to keep the temperature so high that the 

 steam is not condensed. The temperature is 



then raised, so that in the dark the tubes are 

 seen to be at a low red heat, and dry carbon 

 dioxide is passed through. This is said to be 

 reduced by the charcoal to carbon monoxide, 

 which, as affirmed by Mr. Morris, reduces the 

 alumina to aluminum, the metal appearing as 

 a porous, spongy mass. 



Precious Metals. Prof. Chandler Roberts, 

 who is engaged in the study of metals at tem- 

 peratures above their melting-points, has de- 

 scribed some experiments on the mobility of 

 gold and silver in melted lead. If a lump of 

 a gold-lead alloy with 30 per cent, of gold, 

 covered with lead, is heated in a crucible, the 

 gold appears at the surface the very moment 

 when perfect fusion has been attained. The 

 diffusion also takes place rapidly if the gold alloy 

 isputin a small crucible, and this is placed within 

 another crucible containing lead. By melting 

 in a cylinder, 200 millimetres high, a solid cyl- 

 inder of lead with a small piece of the gold 

 alloy fused to its bottom or, better still, by 

 placing the gold at the top of one limb of a 

 U-shaped crucible, and withdrawing test por- 

 tions from the top end of the other limb Mr. 

 Roberts arrived at the diffusion rate, 300 milli- 

 metres in five minutes for gold. Sir William 

 Thomson has characterized this as a great dis- 

 covery, remarking that the rate of diffusion of 

 gold in lead appeared to be immensely greater 

 than the rate of diffusion of liquids. The sub- 

 ject, he said, is one, in fact, of which we under- 

 stand very little, but the property will probably 

 prove of great value in metallurgy, where one 

 example of it, the rapid mixture of spiegelei- 

 sen with iron, is well known. 



Messrs. Bias and Miest have discovered that 

 if, in electrolysis, compressed ores are used as 

 anode in a bath of an electrolyte containing 

 the same metal as the metal of the ore, on the 

 passage of the current the ore is decomposed, 

 the sulphur, etc., being precipitated at the an- 

 ode, while the metal collects at the cathode. 

 When ores containing several metals are oper- 

 ated on, the precious metals, being most easily 

 precipitated, are thrown down first in the me- 

 tallic state at the cathode under the action of 

 a moderate current. The final separation of 

 these metals requires very little battery-power; 

 for the mass of metal, when dissolved under 

 the action of the current, generates sufficient 

 heat for the ulterior separation of each metal. 

 The products at the anode are extracted and 

 purified by treatment with carbon bisulphide, 

 and afterward by separate electrolysis. 



Alloys. Mr. Alexander Dick has produced a 

 new copper-zinc alloy, which he calls Delta- 

 metal, and which, it is claimed, exhibits char- 

 acteristics as essentially superior to brass as 

 those of bronze are to gun-metal. Its advan- 

 tages are great strength and toughness, and a ca- 

 pacity for being rolled, forged, and drawn. It 

 can be made as hard as mild steel, and when 

 melted is very liquid and capable of producing 

 sound castings of close, fine grain. The color 

 can be varied from that of yellow brass to that 



