Aluminium. 181 



The carbonate of soda should be obtained from crystals dried 

 and pulverized fine : the carbon and chalk should also be 

 reduced to powder ; and the whole, as soon as possible after 

 having been mixed, should be made into a paste with very dry 

 oil, and then calcined at a red heat in an iron mercury-bottle, 

 that it may occupy a small space — and thus a larger quan- 

 tity of potassium be obtained by the subsequent process. The 

 calcined mass is subjected to a high heat in an iron mercury- 

 bottle, which is not so rapidly destroyed as might be expected, 

 and ought to last for three or four operations ; it is kept compa- 

 ratively cool by the resulting oxide of carbon, and by the sodium 

 assuming an asriform state, and the heat required is not near so 

 great as might be supposed. An iron tube leads from the bot- 

 tle which is inside the furnace, to a receiver, which is outside, 

 and has an aperture for the escape of the gases. The car- 

 bonic oxide formed from the chalk, assists in carrying the 

 vapour of sodium rapidly into the receiver, and thus prevents 

 it from decomposing any of the gas by which it is necessarily 

 surrounded — an effect that would be facilitated by its finely 

 divided state as vapour ; the receiver also is thus kept hot 

 enough to unite the metallic globules, without a wasteful after 

 process. One-seventh of the weight of the mixture which has 

 been used, or one-fourth of the weight of the carbonate of soda, 

 should be obtained in sodium. If the mixture employed has 

 been such as to melt, it will have prevented a free disen- 

 gagement of the gases. 



To obtain the aluminium. — From 3000 to 5000 grain of 

 chloride of aluminium are placed in a tube of glass or por- 

 celain, about one and a half inches interior diameter, and are 

 insulated by two plugs of asbestos. Hydrogen, purified and 

 dried, by being transmitted through sulphuric acid and chloride 

 of calcium, is sent through the tube : and, while it is passing, 

 the chloride of aluminium is gently heated by a few coals, to 

 drive away any hydrochloric acid which may have been formed 

 by the action of the air on the chloride, and also the chlorides 

 of sulphur and silicium which are invariably present in small 

 quantities. Sodium, previously crushed between two pieces of 

 dry filtering paper, and placed in a boat, is then introduced into 

 one end of the tube while it is still full of hydrogen, and is 

 melted ; the chloride is at the same time heated so as to make 

 it rise in vapour, that it may come in contact with the sodium, 

 and be decomposed; and when the sodium has disappeared, 

 and the chloride of sodium that has been formed is saturated 

 with chloride of aluminium, the process is complete. An in- 

 candescence which occurs is easily regulated. The boat, being 

 taken from the tube, the mixed chlorides, in which the globules 

 of aluminium are suspended, are removed, by dissolving in 

 vol. i. — NO. III. o 



