44' FABRICATION OF SUIPnUKIC ACI»« 



igen and sulphurous acid render the contact more probable, 

 while, as they become less in quantity, the nitrogen, which 

 continues the same, renders their approximation more' dif- 

 ficult. 

 Residuum ni- After the whole of the sulphurous acid is converted into 

 trogen, nitrate sulphuric, the substances that remain are a great deal of ni- 

 and I p t erha°s lde ' tr0 S en 5 nitrous oxide, or nitrous acid gas, if there were at 

 oxigen. first more oxigen than the sulphurous acid required ; and per* 



haps an excess of oxigen more than sufficient to saturate the 

 sulphurous and nitrous acids. 

 Quantity of ox- What is of importance to be observed is the base of the 

 ule of nitrogen n : tr j c ac j(j ? tne quantity of which cannot have varied, and 

 which ought to be as much after the production of all the 

 sulphuric acid as at its extrication from the nitrate of potash. 

 This quantity of nitrous oxide, or nitrous acid, is probably 

 a little less than the nitrate could have produced, because in 

 the combustion the temperature may have been raised too 

 high, and then the complete decomposition of a small por- 

 tion of nitric acid takes place. We say a small portion, 

 because experience has shewn the advantage of keeping the 

 temperature very low by a suitable quantity of moisture. 

 Tlie nitric acid Thus the nitric acid is only the instrument of the com- 



afits as an inter- p] e t c oxigenation of the sulphur ; it is its base, the nitrous 

 medium. r .. . . * ,.. 



acid, that takes oxigen from the atmospheric air, to present 



it to the sulphuric acid in a state suitable to it. 

 Water indirect- We sec that water is not directly necessary to the pro- 

 ly necessary. ducfion of sulphuric acid; its combination with what is 

 formed merely effects the extrication of the nitrous acids 

 that must have combined with it. This gas, thus set free, 

 proceeds afresh to seek oxigen from the atmospheric air con- 

 tained in the receiver, to unite it again with the sulphurous 

 acid. The aqueous vapour has at the same time the double 

 advantage of producing a great commotion in the remaining 

 gases, and of producing this evolution of nitrous acid gas; 

 accordingly its utility has been perceived, and a quantity is 

 introduced, by the exhalations from the hearth, beside that 

 arising from the humidity of the mixture. 



Thus setting out from the existence of nitrous acid and 

 sulphurous acid gases, we have followed the metamorphoses 

 fhese f\yo bodies undergo, taking for our ground-work 



facte 



