FABRICATION OF SULPHURIC ACID. 45 



facts well ascertained; and have admitted only one single 

 supposition, that of the existence of a portion of oxigen 

 still free after the passage of the air over the sulphur. If 

 this supposition should appear doubtful, at least it will cease 

 to be so, when we have shewn by experiment, that, ad- 

 mitting it, every thing takes place as we had conjectured. 



By mixing in a transparent vessel the different substances The whole pro- 

 we have considered as essential to the operation, we can sec ^enTn a glass 

 whether the succession of combinations be such as Ave had vessel. 

 conceived. And it may be verified by putting into a glass 

 body sulphurous acid gas, atmospheric air, and nitrous ox- 

 ide gas in small quantity, for instance J-^ the weight of the 

 sulphureous acid : for we see the oxide grow red, and dif- 

 fuse itself throughout the whole space ; then clouds of white 

 fumes roll across the vessel, and deposit themselves in shi- 

 ning stellated crystals against its sides. These dense whirls 

 of sulphuric are succeeded by an appearance of clearness; 

 and, if at this instant a little water be admitted, the crystals 

 of acid dissolve with great heat ; the nitrous oxide gas, again 

 becoming free, changes afresh to a red vapour; and the 

 same phenomena re-commence, till all the atmospheric oxi- 

 gen is consumed, or all the sulphurous acid burnt. 



The remaining gases are precisely those we mentioned in 

 our conjectures ; for the colour of the nitrous acid appears 

 with almost all its first intensity; and after the operation is 

 completed, there is no more smell of sulphurous acid, but 

 a great deal of nitrogen, and of oily sulphurous acid on the 

 sides of the glass. 



If in this combustion of the sulphurous acid there were Too much 



too much contact between the eases and the water added, water would 



• • _, produce nitric 



either by great agitation of a little, or by the presence of a acid. 



large quantity, the operation would be very slow and in- 

 complete, because liquid nitric acid would be formed, which 

 retaining its state, would have very little action on the gas 

 to be organized. * 



* It sometimes happens, that the decomposition of the nitrous The experi- 



acid gas is carried so far as to the state of an oxidule of nitrogen ; "? ent does not t 

 tv. . . .-, , always succeed. 



this too appears to arise from too great action of the water on this 



gas. Messrs. Berthollet and Guyton have ascribed to this the mis- 

 carriage of the experiment, wh^n the contact of water is too great. 



This. 



