722 ALUMINUM. 



distilled. Through tubes in stationary covers the distilled metal passes 

 to condensers, where it is solidified. When the process is completed, 

 the crucible is lowered and a new one with a fresh charge is substituted 

 and raised into the furnace. The residues are carbonate of soda and 

 metallic iron, both of which can again be utilized. The process is as 

 simjile as it is ingenious, and the temperature required is very moderate, 

 the sodium distilling as eazily as zinc. One charge requires about an 

 hour, and a battery of four furnaces can yield a ton of sodium a day. 

 The metal is kept from oxidation by a covering of mineral oil till used. 



The Deville-Castner process takes the double chloride finely divided 

 and mixed with thin slices of sodium, and empties the mixing cylinder 

 on the hearth of a reverberatory furnace, where the mass quickly melts, 

 and a re-action takes place that finally liberates a silvery stream of 

 molten aluminum, that is drawn out from below, while the melted slag 

 runs off from above. The first run is purest and contains about three- 

 fourths of the charge. The remainder is scraped oft' from the hearth, 

 or found entangled with the slag, from which it has to be separated. 

 The aluminum is finally re-melted in plumbago crucibles, and cast into 

 ingots, bars, or plates. 



The Journal of the Society of Arts, from whose very extended account 

 the foregoing is abridged, adds that day by day, as the manufacture 

 progresses, improvements are made which either enhance the economy 

 of production or the purity of the product, and speaks in the highest 

 praise of the skill, energy, and perseverance of Mr. Castner and his 

 assistants, by whom, more than any others, aluminum has been brought 

 into the market on commercially practicable terms and in a condition 

 of almost perfect purity. 



Grabau's process may be briefly described. Powdered cryolite put 

 into a solution of the sulphate of aluminum gives by re-action the fluoride 

 of aluminum, which is then heated till ready to evaporate. The heated 

 fluoride is pulverized and thrown upon melted sodium contained in a 

 vessel lined with cryolite. The heat generated by the violent re-action 

 melts the aluminum as well as the cryolite ; and the molten mass being 

 poured out, the pure aluminum settles at the bottom, while the cryolite 

 is at the top. The main advantage of this method over the Castner 

 process is that it goes on at a lower temperature and is extremely simple. 



Numerous other processes are described by Richards in his exhaustive 

 work on the subject ; c. (/., reduction by cyanogen, by hydrogen, by car- 

 buretted hydrogen, by carbon and carbon-dioxide, concerning all of which 

 Dr. T. Sterry Hunt remarks that " there has been no pure aluminum 

 made commercially save from the chloride by the use of sodium." Web- 

 ster is the chief manufacturer in England on his own patents, and large 

 works have been erected in France on Buuseu and Deville's process by 

 electrolysis. 



But after all, the only true rival of the Castner-Deville process seems 

 to be the Hall process, on patents of Charles M. Hall, and carried on by 



