284 



PRINCIPLES OF CHEMISTRY 



The preceding series of changes serve as the basis of the manu- 

 facture of sulphuric acid or so-called chamber acid. This acid is 

 prepared on a very large scale in chemical works because it is the 

 cheapest acid whose action can be applied in a great number of cases. 

 It is thus used in immense quantities. 



The process is carried on in a series of chambers (or in one divided 

 by partitions as in fig. 50, which shows the beginning and end of a 

 chamber) constructed of sheet lead. These chambers are placed one 



FIG. 50. Section of sulphuric acid chambers, the first and last chambers only bein^ represented. 

 The tower to the left is called the Glover's tower, and that on the right the Gay-Lusaac'B rower. 

 Less than -^ of the natural size. 



after the other, and communicate with one another by tubes or special 

 orifices so placed that the inlet tubes are in the upper portion of the 

 chamber, and the outlet in the lower and opposite end. The current of 



phuric acid (for forming 2H 2 SO 4 with water), besides l equivalents (24 parts) for con- 

 verting the iron into oxide, Fe 2 O 3 ; hence the combustion of the pyrites for the formation 

 of sulphuric acid and ferric oxide requires the introduction of an equal weight of oxygen 

 (120 parts of oxygen to 120 parts of pyrites), or five times its weight of air, whilst four 

 parts by weight of nitrogen will remain inactive, and in the removal of the exhausted 

 air will carry off the remaining nitric oxide. If not all, at least a large portion of the 

 nitric oxide may be collected by passing the escaping air, still containing some oxygen, 

 through substances which absorb oxides of nitrogen. Sulphuric acid itself may be 

 employed for this purpose if it be taken as the hydrate H 2 SO 4 , or containing only a 

 small amount of water, because such sulphuric acid dissolves the oxides of nitrogen, 



