ALKALIES. 257 



vegetable life, they should become constituent parts of plants. It has 

 been already stated, that hydrogen has been supposed by some, to 

 be one of their constituent principles ; a suggestion which is coun- 

 tenanced by their levity, and by the fact, so contrary to what is found 

 to be true in most other cases, that their oxides are heavier than the 

 metals which they contain.* 



SEC. IV. LITHIA. 



1. NAME. From Xidos, a stone, or Xidsios, stony. 



2. DISCOVERY. 



Detected in the year 1818, by Mr. Arfwedson, in the petalite, which 

 contains from 3 to 8 per cent. ; in the triphane or spodumene, ) there 

 is 8 per cent, and in crystallized lepedolite, 4 per cent. ; it has been 

 found also in the green and red tourmaline, and in several varieties 

 of mica. 



3. PROCESS. 



(a.) Fuse the powdered petalite, 1 part, with carbonate of pot- 

 ash 3 parts, dissolve in muriatic acid evaporate to dryness digest 

 in alcohol, which takes up the muriate of lithia and little else ; this so- 

 lution is evaporated to dryness, and the residuum again dissolved in 

 alcohol, which gives the muriate pure ; it is then digested with car- 

 bonate of silver, to form carbonate of lithia ; this being decomposed 

 by lime or barytes, gives pure lithia, which must be evaporated to 

 dryness, away from the air.J 



(6.) Another process by Berzelius, is as follows : Mix 2 parts of 

 fluor spar, and 3 or 4 of sulphuric acid, with 1 of powdered petalite 

 or spodumene, and apply heat till the acid vapors, consisting princi- 

 pally of silicated fluoric acid, have ceased ; thus the silica is remov- 

 ed, and the alumina and lithia unite with the sulphuric acid, in the 

 form of sulphate ; that of alumina is decomposed, and the earth pre- 

 cipitated by boiling with pure ammonia. Ignition expels the sul- 

 phate of ammonia, and the pure sulphate of lithia remains, which is 

 easily converted into the carbonate, and the carbonic acid being ex- 

 pelled from this, we obtain the pure lithia. 



* It is however sufficient to caution us against admitting conjectures in such cases, 

 that soda was formerly suspected to be composed of magnesia and nitrogen, and 

 Fourcroy, in his large work, has stated the reasons why he with some other chem- 

 ists, conjectured that potash was composed of lime and nitrogen, and soda of magne- 

 sia and nitrogen. 



t In the spodumene and petalite, the lithia is combined with silica and alumina; 

 but in the lepidolite and in the lithion mica, it is combined also with potassa, and to 

 avoid contamination with this alkali, the lithia should be prepared from the spodu- 

 mene and petalite. Turner. 



t For other processes, see Ann. de Chim. et de Phys. X. 86 ; also, Henrv, Vol. I, 

 p. 572, and Thenard, Vol. II, p. 323,4th Ed. ; Ure's Diet. 3d Ed. p. 582. * 



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