378 Prehniie-^ Olivine. 



with which the silicium may be mechanically mixed. No acid 

 attacks it any further, except a mixture of fluoric and nitric 

 acid, which dissolves it readily. With the carbonates of the 

 fixed alkalies it detonates before the heat has attained to red- 

 ness, extricating from them ihe carbonic acid ; but it does 

 not decompose saltpetre below incaisdescence. It detonates, 

 even by means of the carbonates, in (he midst of melted salt- 

 petre. With sulphur It combines at a very high temperature; 

 the sulphuret is white and earthy, and soluble in water, with 

 the disengagement of sulphuretted hydrogen. It burns also 

 in chlorine. The chloride of silicium is a very volatile li- 

 quid, giving out fumes which are decomposed by water, and 

 give silex and muriatic acid gas. 



1 have reduced also zirconium, by treating the double flu- 

 ate of zircon and of potash, with potassium. The zirconium 

 is a black powder, very combustible, insoluble in acids, as 

 well in the nitric as the nitro-muriatic, but soluble in the fluo- 

 ric. It presents the curious phenomenon of burning, with ex- 

 plosion, in a vacuum; the reason is, that it commonly con- 

 tains a small portion of hydrate of zircon, the water of which 

 oxidizes the zirconium. 



The other earths have not given precise results. 



13. Prchniie-— Olivine.'^ — A very elaborate examination of 

 several varieties of Prehnite has been made under the direc- 

 tion of L. P. Walmstcdt, professor of chemistry in the uni- 

 versity of Upsal, by MM. P. F. Wahlberg, J. A. Hceger, and 

 S. A. Varenius, candidates for the philosophical degree. 

 The very discordant results, obtained by the different chem- 

 ists who had analyzed this mineral, induced these gentle- 

 men to make it the subject of their experiments. The 

 analyses of two varieties of prehnite made by Gehlen, and 

 published in 1813, afforded results similar to each other — 

 very different, however, from the results obtained by other 

 analysts. The analyses of several varieties, which were 

 subjected to the rigid examination here noticed, all afforded 

 results which coincided very nearly with the analyses of 

 Gehlen. It appears therefore that the accuracy of Gehlen's 

 analyses is pretty fully established, together with the fact 



* For the tAVo valuable tracts here noticed, one of which consists of 

 twenty and the other of six pages, quarto, the editor is indebted to Prof. 

 Berzelius, of Stockholm. 



