Sulphuric Acid-manufacture. 25 



chemical treatises this fact is distinctly stated. Thus Miller, 

 in his ' Elements of Chemistry/ speaking of the theory of the 

 manufacture of sulphuric acid, says : — " Direct combination, 

 however, cannot be produced between the two gases (oxygen and 

 sulphurous acid) ; the intervention of a third substance becomes 

 necessary, and if ivater be presented to them a very gradual pro- 

 cess of oxidation occurs.' 3 



Gmelin also, in his l Handbook of Chemistry/ observes : — 

 u A dry mixture of two measures of sulphurous acid gas and one 

 measure of oxygen remains unaltered ; but if water be present, a 

 very gradual condensation takes place, and sulphuric acid is 

 produced/" The results arrived at by different observers may 

 be summed up in the deduction from the above paragraphs — 

 namely, That no action can take place behveen these two gases 

 without the intervention of water, either in the liquid or gaseous 

 state. 



It was with the intention of inquiring more closely into this 

 that the following experiments were made ; and the conclusion 

 I come to, and which I hope to clearly demonstrate in this 

 paper, is the very reverse of that generally admitted — That 

 action does take place between the dry gases under certain con- 

 ditions. 



As I was anxious to have the gases in as similar a condition 

 as possible to those in the lead chamber, the sulphurous acid 

 was made from burning sulphur, the nitric acid being prepared 

 from nitrate of soda by the action of sulphuric acid, whilst the 

 air employed was first carefully dried by passing through sul- 

 phuric acid and caustic potash, every care being taken to prevent 

 the presence of even the smallest amount of moisture. 



Exp. I. When dry sulphurous acid and nitric acid in the 

 gaseous form are brought into contact in a perfectly dry glass 

 vessel, which is then hermetically sealed, there is apparently no 

 action (for this experiment I used a vessel of the following 

 shape) ; but if this mixture, after being allowed 

 to stand for ten or twelve days, be then opened, ^y 

 and the remaining gases expelled, it is found 

 that a decided, though small amount of sulphuric 

 acid has been formed over the sides of the glass vessel, and may 

 be seen in the condition of white crystals, soluble in water, and 

 behaving in all respects as sulphuric acid. There are many 

 things which will prevent this formation, and which I intend 

 noticing further on, such as temperature &c. This result, how- 

 ever, is greatly hastened by the addition of a single drop of 

 water on the end of a fine platinum wire. 



The conclusion one was apt to arrive at was that these crys- 

 tals were merely the ordinary chamber crystals ; but I was led 



