88 NON-METALS AND THEIR COMBINATIONS. 



Sulphur trioxide, S0 3 = 80 (Anhydrous sulphuric add}. This is 

 a white, silk-like, solid substance, having a powerful affinity for 

 water; it may be obtained by the action of phosphoric oxide on 

 strong sulphuric acid; it is merely of scientific interest. 



Sulphuric acid, Acidum sulphuricum, H 2 S0 4 = 98 (Oil of vitriol, 

 Hydrogen sulphate). There is no other acid, and perhaps no 

 other substance, manufactured by chemical action which is so 

 largely used in chemical operations, and in the manufacture of 

 so many of the most important articles, as sulphuric acid. 



Sulphuric acid was accidentally discovered in the fifteenth 

 century by Basile Valentine, a very laborious monk, who ob- 

 tained it by heating ferrous sulphate (green vitriol) in a retort. 

 To the liquid distilling over he gave the name oil of vitriol, in 

 allusion to the thick or oily appearance, and the green vitriol 

 from which it was obtained. The article of commerce called 

 Nordhausen oil of vitriol, or fuming sulphuric acid, is yet made by 

 this process of heating ferrous sulphate. The acid thus obtained 

 is sulphuric acid, containing some sulphur trioxide (H 2 S0 4 .S0 3 ). 



Sulphuric acid is found in nature in combination with metals 

 as sulphates. Thus calcium sulphate (gypsum), barium sulphate 

 (heavy-spar), magnesium sulphate (Epsom salt), and others occur 

 in nature. 



Manufacture of sulphuric acid. Sulphuric acid is manufactured 

 on a very large scale by passing into large leaden chambers 

 simultaneously, the vapors of sulphur dioxide (obtained by 

 burning sulphur or pyrites in furnaces), nitric acid, and steam, 

 a supply of atmospheric air being also provided for. The 

 oxygen of the nitric acid oxidizes the sulphur dioxide, which, 

 at the same time, takes up water: 



S0 2 + + H 2 = H 2 SO 4 . 



Only a portion of the oxygen necessary for oxidation is de- 

 rived from nitric acid directly; the larger quantity is obtained 

 from the atmospheric air, the nitrogen dioxide serving as an 

 agent for the transfer of the atmospheric oxygen. 



By the action of nitric acid on sulphurous acid, are formed 

 sulphuric acid, water, and nitrogen dioxide: 



3H 2 SO 3 -f 2HNO 3 = 3H 2 SO 4 -f H 2 O + 2NO. 



