1818.] the Commencement of the Year 1817. Part I. 15 



scarcely soluble in alcohol. It crystallizes in needles, which 

 gradually accumulate in such a way as to form globular crystals 

 in which the fibrous structure cannot be detected even by a 

 microscope. 



If a little muriatic acid be poured into a seleniate, and then a 

 plate of zinc be introduced into it, the selenium is precipitated in 

 the metallic state. The zinc appears at first as if it were covered 

 with a pellicle of copper ; then the selenium is deposited in red 

 flocks. If sulphuric acid be substituted for muriatic, the preci- 

 pitation goes on with more difficulty. The precipitate assumes a 

 grey colour, and contains sulphuret of selenium. If a current of 

 sulphureted hydrogen gas be made to pass through a solution of 

 selenic acid in water, the selenium is precipitated of an orange 

 colour; but becomes red when dried. When heated it melts, 

 may be distilled over, and forms an orange-coloured transparent 

 matter.— (See Annals of Philosophy, xi. 291 ; and Ann. de 

 Chim. etdePhys. vii. 199.) ' 



VI. ALKALIFIABLE COMBUSTIBLES. 



1. Lithina, a new fixed Alkali.— Vox this very interesting 

 discovery we are indebted to M. Arfvredson, an ingenious pupil 

 of Berzelius. He found it in a mineral first observed by M. 

 d'Andrada in the mine of Uto, in Sweden, and called by him 

 petalite. This mineral, according to the analysis of Arfvredson, is 

 composed of 



Silica 80 



Alumina 17 



Lithina 3 



100 



This new alkali is extracted from the petalite in the usual way, 

 by calcining the mineral in powder with carbonate of barytes, 

 separating all the earths, and obtaining the alkali united to an 

 acid. M. Arfvredson suspected at first that it was soda ; but 

 was induced to subject it to a more rigid examination from the 

 great capacity for saturation which it displayed. The result was 

 the discovery of its peculiar nature. The following are the most 

 remarkable characters of this alkali. 



Most of its combinations with acids are very fusible. The 

 sulphate and muriate liquify long before they are heated to red- 

 ness. The carbonate melts just when red hot, and in that state 

 attacks the platinum crucible almost as violently as the nitrate 

 of another alkali. The sulphate crystallizes readily, and the 

 crystals contain no water of ciystallization. Their solution is 

 neither precipitated by muriate of platinum, nor by tartaric acid. 

 The muriate is very deliquescent; more so, perhaps, than muriate 

 of lime. The nitrate crystallizes in rhomboids, and attracts moist- 

 ure rapidly. The carbonate is soluble with difficulty in water. 



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