378 Prehnite— Olivine. 
with which the silicium may be mechanically mixed. No acid 
attacks it any further, except a mixture of fuorie and nitric 
acid, which dissolves it readily. With the carbonates of the 
fixed alkalies it detonates before the heat has attained to red- 
aay extricating from them the carbonic acid; but it does 
ot decompose saltpetre below incandescence. tt detonates, 
even by means of the carbonates, in the midst of melted salt- 
petre. With sulphur it combines at a very high temperature; 
the sulphuret is white and carthy, and soluble in water, with 
the disengagement of sulphuretted hydrogen. It burns also 
in chlorine. The chloride of silicium is a very volta” 
quid, giving out fumes which are decomposed by water, | 
give silex and muriatic acid gas. ; 
have reduced also zirconium, by treating the double ; 
ate of zircon and of potash, with potassium. The zirec 
isa black powder, very combustible, insoluble in acids, as 
well in the nitric as the nitro-muriatic, but soluble in the fiuo- 
ric. {It presents the curious phenomenon of burning, with ex- 
plosion, in a vacuum; the reason is, that it commonly con- 
ins a small potion of hydrate of zircon, the water of which 
sidizes the zircon 
~The other earths ‘nae nat given precise results. 
ae 
43. Pr ehnite—Olivine.*—A very elaborate examination of 
several varieties of Prehnite has been made under the direc- 
tion of L. P. Walmstedt, professor of chemistry in the uni- 
versity of Upsal, by MM. P. F. Wahlberg, J. A. Heeger, and 
5. 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 prelinite 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 
a For the two valuable tracis here noticed, one of whieh consists of 
twenty and the other of six pages, quarto, the editor is indebted to Prof. 
Berzetius, of Stockholm. 
