OXIDES AND OXYGEN ACIDS OF SULPHUR 265 



dride N 2 3 * (see p. 314), and oxygen. These are obtained, the 

 first by injection of steam, the second usually by the burning of 

 pyrite, the third from nitric acid HN0 3 , and the fourth by the 

 introduction of air. The gases are thoroughly mixed in large 

 leaden chambers, and the sulphuric acid forms droplets which fall 

 to the floors. In spite of elaborate investigations, instigated by 

 the extensive scale upon which the manufacture is carried on and 

 the immense financial interests involved, some uncertainty still 

 exists in regard to the precise nature of the chemical changes which 

 take place. According to Lunge, supporting the view first sug- 

 gested by Berzelius, the greater part of the product is formed by 

 two successive actions, the first of which yields a complex com- 

 pound that is decomposed by excess of water in the second: 



0-H 



H 2 O + 2S0 2 4- N 2 3 + O 2 -> 2SO 2 ' (1) 



X 0-N0 



The group NO, nitrosyl, is found in many compounds. Here, 

 if it were displaced by hydrogen, sulphuric acid would result. 

 Hence this compound is called nitrosylsulphuric acid : 



,,0-H ,OR 



2SO/ +H 2 0^2S0 2 ( + N 2 3 . (2) 



X 0-N0 X OH 



The equations (1) and (2) are not partial equations for one inter- 

 action, but represent distinct actions which can be carried out 

 separately. In a properly operating plant, indeed, the nitrosyl- 

 sulphuric acid is not observed. But when the supply of water is 

 deficient, white " chamber crystals/' consisting of this substance, 

 collect on the walls. 



The explanation of the success of this seemingly roundabout 

 method of getting sulphuric acid is as follows: The direct union of 



* This gas is unstable, breaking up in part into nitric oxide NO and nitro- 

 gen tetroxide NO 2 : N 2 O 3 =* NO + NO 2 . In this process, however, the mix- 

 ture behaves as if it were all N^Os, and so only nitrous anhydride is named in 

 this connection. 



