848

SODIUM.— Manufacture of.

tion of potassium are applicable also, with slightmodifications, for the preparation of sodium. Theapparatus required is also of exactly the samedescription as in the case of potassium. The sub-stances employed may be either sodium hydrate andiron, or sodium carbonate and charcoal. These areplaced in a malleable iron bottle—those in whichmercury is imported answer admirably—and heatedto whiteness in a powerful blast furnace. The gas,which is evolved at the beginning of the process, isof a yellow colour ; this is allowed to escape into theair, the receiver not being adapted to the retort tilla cold iron rod thrust into the bottle comes outcovered with globules of sodium, which take fire inthe air. The sodium vapour is then conducted into areceiver (which may be of iron or copper) containingmineral naphtha or rock oil; it is kept cold by sur-rounding it with cold water, which is frequentlychanged. It should, of course, be provided with avent for the escape of the incondensable gasesevolved during the decomposition. The operation ismuch more productive than in the case of potassium,because the sodium does not combine with carbonicoxide.

The decomposition either of sodium hydrate bymetallic iron, or of carbonate of soda by charcoal, is,however, effected with greater difficulty than is thecase with the corresponding potassium salts. By mix-ing the sodium hydrate or carbonate of soda with alittle potassium hydrate or carbonate of potassium,the operation is effected with greater facility; butthe metal obtained is then a brittle alloy of sodiumand potassium. From this, however, the whole ofthe potassium may readily be separated by meansof slow oxidation, without any considerable loss ofsodium. To effect this, the alloy is formed intoplates and placed in a large bottle; these are coveredwith naphtha, and the air in the bottle is occasionallyremoved. After a few days the whole of the potas-sium will have disappeared, and pure and veryductile sodium remains. In Schoedler’s processthe carbonate of soda used is obtained by the igni-tion of sodium acetate, free access of air beingavoided. The object of this is to obtain the car-bonate in a very pure state, since, if sodium sulphatebe present, it becomes reduced in the process tosodium sulphide, which acts strongly on the ironbottle. The mixture of carbonate of soda and char-coal obtained is mixed with a fourth of its weight ofcharcoal in fine powder, and with double this quan-tity of charcoal in a coarse state, to prevent fusionof the mass. Should this occur, the fused con-tents spirt into the tube and choke it up. Themixture, heated in the iron bottle, yields pure sodium,with a very small residue of carbon, &c.

The process now commonly employed for thepreparation of sodium was devised by II. St. C.Deville. Crystals of sodium carbonate are cal-cined, powdered, and mixed with a slight excessof powdered charcoal or coal: chalk is also addedto keep the mixture fluxed during the process.In preparation in small quantity the proportionsare:—

Dry carbonate of soda,. 717 parts.

Charcoal,. 175 u

Chalk,. 108 “

When the continuous process is used, which willbe described further on, the proportions are:—

Dry carbonate of soda. 30 parts.

Charcoal,. 13 “

Chalk,. 3 “

The materials are pounded and sifted, then mixedby hand and again sifted, in order to insure theirintimate association. The mixture must be used assoon as made, lest moisture be absorbed. It is alsoconsidered advantageous, when circumstances per-mit, to calcine the whole mass before introducing itinto the distilling apparatus; since it is thereby ren-dered much more compact, and a larger quantitycan be operated on in a vessel of a given size.

The distillation is performed either in a mercurybottle or in iron cylinders of large dimensions. Thereceiver preferred by Deville is that designed byMaresca and Donny for the condensation of pot-assium. These receivers are made of two plates ofiron from one-twelfth to one-eighth of an inch thick:one of them, A, Fig. 1, is turned up at the edges,while the other, B, is left flat, except at the end, C,where both plates are formed into a cylindrical neck,1 inch in internal diameter. The conical portion,which joins the cylindrical neck to the flat body ofthe receiver, should be made as short as possible.

Fig. 2. Fig. 1.

Fig. 3.

The two portions when joined form a rectangularbox with a cylindrical neck. These receivers areeither left completely open at the back (Fig. 2), orthey are closed at the back, with the exception of asmall aperture near the top, Fig. 3. The plates areheld together by iron clamps.

With the first apparatus (Fig. 2) the condensedsodium (so soon as the receiver becomes hot enoughto retain it in the liquid state) flows off as fast asproduced; with the second (Fig. 3) the sodium fillsthe receiver, which is then removed.

When the process goes on well the sodium is verypure. Some impure sodium remains attached tothe plates of the receiver; lienee the plates shouldalways be scraped before again using them, thematter scraped off being received under roek oil,and redistilled.

The temperature absolutely required for the re-duction of sodium carbonate is about that required