SULPHURIC ACID

or Oil of Vitriol (H280.), the most important of all chemical products, on whose use nearly all industries depend; a colorle , oily hygroscopic and corrosive. It is manufactured by two methods: (1) the lead chamber proce , suitable | for low strengths; (2) the ‘contact’ proce , more efficient for high concentrations. The manufacture of the fertilizers ammonium sulphate and superphosphate consume about 60 per cent. of the weaker chamber acid, while for the explosives and dye industries the higher concentrations are nece ary. Lead Chamber Proce .—Sulphur di- ‘oxide obtained by burning iron pyrites in special burners is pa ed into lead chambers along with steam or sprayed water and nitrous gases (catalyst) derived from nitric acid or oxidized ammonia; 70 per cent. chamber acid condenses on the floors and is concentrated to 79 per cent. in lead pans. For further concentration, gla and platinum ve els are now replaced by fused silica arranged as a cascade, where sprayed acid meets hot gases, Contact Proce .—In the presence of hot Platinized asbestos (catalysis), sulphur dioxide and oxygen unite to form sulphur trioxide, which combines with water to give sulphuric acid. In practice 97 per cent. acid is used to absorb the sulphur trioxide forming 100 per cent. acid. By further absorption fuming sulphuric acid or oleum is produced.