CHEMICAL SCIENCE. 307 



If a sandstone, cemented by carbonate of lime, is exposed to a high tem- 

 perature, silicate of lime would be produced by combination of silex with the 

 lime, and carbonic acid gas would be disengaged. 







ON THE GASEOUS PRODUCTS OF VOLCANOES. 



The following investigations of the gaseous products of the volcanic moun- 

 tains of Italy, were made by M. Deville, in common with Lcblanc and Se- 

 wy : 1 . Gas which was collected in May, June, September and October 

 1855, at various points of the stream of lava from the eruption of Vesuvius, 

 on May 1,1 855. The analyses of this gas showed that the gas which issues 

 from those fumaroles which have been called dry fumarolcs, and which only 

 carries with it anhydrous alkaline chlorides and small quantities of sulphates, 

 is nothing but a stream of air either unaltered or containing less oxvffen, 



* O ' 



thus 20'1 and 2O6 per cent of oxygen were found in it. The same is the 

 case with the gas loaded with vapors of muriate of ammonia, which was ex- 

 pelled from the lower parts of the lava in October. 2. Gas collected in 

 September from the fumaroles on the small plain in the centre of the upper 

 crater of Vesuvius. This gave aqueous vapor of the temperature of 140 deg. 

 to 174 deg. F., mixed with a little vapor of sulphur and sulphuretted hydro- 

 gen. In one sample of this gas 3'51, in another 9 26 per cent, of carbonic 

 acid were found. The remainder was only air, from which nearly all oxy- 

 gen was extracted. 3. Gas collected in September and October, from those 

 fumaroles on the summits of Vesuvius and Etna which throw up a mixture 

 of aqueous vapor, muriatic acid, and sulphurous acid, at high temperatures, 

 194 deg, 257 deg., and 356 deg. F. This again is nothing but air partially 

 deprived of oxygen. 4. Gas collected in September 1855, on the upper 

 border of the cone of eruption of Etna (1852). This upper margin, in June, 

 still possessed an abundance of fumaroles of sulphuretted hydrogen of 1 82 

 deg. F. In September, they only emitted aqueous vapor of 142 deg. F. ; 

 which was perfectly neutral, and the vapor was only accompanied by air. 

 The constitution of these gases, which escape from the summits of Vesuvius 

 and Etna, is such as we might have expected. Air is always intermixed 

 with the gases ; and the emanations of carbonic acid, sulphur, sulphuretted 

 hydrogen, muriatic acid, and sulphurous acid, are products such as the cleft 

 crater must furnish in the same way as a cracked chimney over a fire. 

 5. Gas collected on the 5th and 22d of October, in the Lago di Nafda or Lac 

 di Palici in Sicily. The composition of this gas varies with time. In none 

 of the gases could a combustible gas be detected. With reference to the 

 solid productions of the eruption of 1855 : two kinds of lava flowed out in 

 this eruption. The one which made its appearance last is dark, as it were 

 furnished with a glassy coating, and has no action upon the magnet ; while 

 the other kind is gray, much more crystalline, and strongly magnetic. Both 

 contain nearly the same amount of iron, so that the iron is not contained in 

 the same form in the lavas. The one contains T4, the other 2'2 per cent, of 

 phosphoric acid. Both contain some chlorine, a portion of which is as it 

 were mixed in the form of a soluble chloride, whilst another portion is not 

 washed out with water, but only obtained by the decomposition of the mine- 



