Reactions of the chamber process. In a very general way, the various reactions which take place in the lead chambers may be expressed in two equations. In the first reaction sulphur dioxide, nitrogen peroxide, steam, and oxygen unite, as shown in the equation
(1) 2SO2 + 2NO2 + H2O + O = 2SO2 (OH) (NO2).
The product formed in this reaction is called nitrosulphuric acid or "chamber crystals." It actually separates on the walls of the chambers when the process is not working properly. Under normal conditions, it is decomposed as fast as it is formed by the action of excess of steam, as shown in the equation
(2) 2SO2 (OH) (NO2) + H2O + O = 2H2SO4 + 2NO2.
The nitrogen dioxide formed in this reaction can now enter into combination with a new quantity of sulphur dioxide, steam, and oxygen, and the series of reactions go on indefinitely. Many other reactions occur, but these two illustrate the principle of the process.
The relation between sulphuric acid and nitrosulphuric acid can be seen by comparing their structural formulas:
| O= -OH | O= -OH |
| S | S |
| O= -OH | O= -NO2 |
The latter may be regarded as derived from the former by the substitution of the nitro group (NO2) for the hydroxyl group (OH).
