24 Mr. H. A. Smith on the Chemistry of 



respects very much behindhand. Experiments have certainly 

 been made, and great successes have been achieved on all sides ; 

 but these have tended more to broad generalizations than to 

 exact chemical facts — to the manufacturing, not to the scientific 

 side of the question. The interior of the lead chamber is 

 comparatively an unknown land to us. Lowthian Bell has 

 lately traced the actions occurring in his blast furnace through 

 every stage, from the bottom to the top, in a series of most 

 laborious experiments ; but no one has yet done this with the 

 sulphuric acid-chamber. I now venture to hope that this very 

 limited attempt to at least commence such an investigation 

 may be of interest, not only to those engaged in the manu- 

 facture, but to those who only look at it from a scientific 

 point of view. 



In observing the theory of the manufacture of sulphuric acid, 

 there were many points which it struck me would well repay a 

 closer examination. It is well known that when sulphurous acid 

 comes into contact with one of the high oxides of nitrogen, it 

 deprives it of its oxygen, provided the contact takes place in the 

 presence of steam. But there are many causes which prevent 

 this action ; and it is not an uncommon thing to see this experi- 

 ment fail. 



If the heat of the vessel in which the combination is to take 

 place be too high, or if it be not high enough, the result will be 

 failure. And so in practice: every manufacturer knows how 

 careful he must be in regulating the amount of steam he throws 

 into his chamber ; otherwise he finds a great amount of sulphu- 

 rous acid escaping into the atmosphere, a larger amount of 

 nitrous fumes in the acid from his Gay-Lussac Tower, and a 

 smaller yield of vitriol. 



It is into the laws which regulate the combination of those 

 gases that I wish to inquire ; and I have tried to do so, first, by 

 individual experiment, and then by a careful examination of the 

 lead chamber in which the action takes place. 



On the Action of Sulphurous Acid Gas upon Nitric Acid Gas. 



Although we are indebted to the labours of Clement, Des- 

 ormes, Davy, De la Provostaye, and others for the light which 

 has been thrown upon the theory of this action, so far as it 

 relates to sulphuric acid- manufacture, yet I trust I may be 

 excused for bringing forward results which differ in some degree 

 from those of the above-mentioned workers. 



It is generally understood at the present day that no action 

 can take place between dry sulphurous acid and nitric acid 

 gases when brought together in the same vessel ; and in all 



