Inlelligence and Miscellaneous Articles. 469 



times sufficiently high to occasion the combustion of the coal-beds 

 which are near the surface, and the products of the combustion of the 

 coal are added to the vapour of water and of sulphuric acid, and thus 

 increase the grandeur of the phtenomenon. The sulphuric acid which 

 arises under the conditions described, exerts a very energetic action 

 on the mineral and organic substances which it meets with in its 

 passage ; the trunks of the trees which occur in the neighbourhood 

 of the burning mountain are covered with the black colour of sub- 

 stances which have been immersed in sulphuric acid. Mineral sub- 

 stances are also strongly acted upon by this powerful acid, which 

 simultaneously attacks silica, alumina, lime, oxide of iron, the earths 

 and alkalies which enter into the composition of rocks, and eventually 

 sulphates are produced, among which is the double sulphate of pot- 

 ash and alumina (alum) in sufficient quantity to be useful. 



The author analysed the efflorescences collected on the burning 

 mountain of Cransac. These efflorescences were w^hite, strongly 

 acid, reddened tincture of litmus, and attracted moisture from the 

 air. After drying in vacuo by the air-pump, 50 grammes were dis- 

 solved in a litre of distilled water, and the solution was treated as if 

 it had been a common mineral water 



The results of the analyses were : — 



Sulphate of potash and alumina . . 24*25 



Sulphate of alumina . . . , . . 53" 31 



Sulphate of magnesia 3*47 



Sulphate of manganese ..... 1*35 



Sulphate of iron 10"29 



Free sulphuric acid , 7'33 



100-00 

 On examining the natural process which gives rise to the large 

 quantities of sulphuric acid, occurring not only combined with bases, 

 but also uncombined, it occurred to M. Blondeau to examine whether 

 under similar conditions sulphuric acid might not be immediately pro- 

 duced from sulphurous acid gas. 



For this purpose some argillaceous sand was put into a porcelain 

 tube, one of the ends of which communicated with two vessels, from 

 one of which sulphurous acid, and from the other vapour of water 

 was disengaged, and at the same time air was passed into the in- 

 terior of the apparatus by means of a gasometer. At the other end of 

 the porcelain tube a bent tube was adopted, which was immersed in 

 water in a two-necked bottle, to one of which was fixed a disengaging 

 tube. The apparatus thus arranged, the porcelain tube was sur- 

 rounded with burning charcoal, so as to heat it to dull redness, and 

 the sulphurous acid gas, air and the vapour of water were slowly 

 passed into it. The substance disengaged at the end of the tube was 

 sulphuric acid ; taking care to supply an excess of air, but very little 

 sulphurous acid is disengaged, the whole of it being converted into 

 sulphuric acid. 



To gu from this laboratory experiment to a manufacturing one, 

 sulphurous acid must be produced by the combustion of sulphur or 



