358 JOSEPH STRUTHERS 



of pyrite in New York state, and also of the lean cupriferous 

 pyritic ores of the New England states. Where the conditions 

 are favorable for deep mming and concentration and for ship- 

 ment to the numerous paper mills of that section, constant 

 and large supplies of sulphur will thus be guaranteed at prices 

 much lower than can be expected from outside sources. 



The manufacture of sulphuric acid is of great industrial 

 importance, as the acid is of primary importance in the manufac- 

 ture of phosphate rock fertilizers and in the refining of petro- 

 leum. It is also required in the manufacture of other acids and 

 chemical salts, and has a very wide field in the making of alizarin 

 dyes, artificial indigo, and many other important chemical 

 salts. Of the immense quantities of sulphuric acid made 

 yearly, the greater part does not appear on the market ; because 

 of the expense and difficulty of shipping it, consumers of large 

 amoimts generally make their own acid. 



Until a few years ago the total quantity of ordinary sul- 

 phuric acid produced in the world had been obtained by burning 

 crude sulphur in air, the resultant sulphur dioxide gas being 

 then passed, together with steam and an oxidizing agent, gener- 

 ally nitric oxide, into lead-lined chambers, where these gases 

 react on one another and form the dilute acid, which is subse- 

 quently purified and concentrated to the desired degree of 

 strength. This process is called the lead-chamber process, but 

 a newer and more satisfactory process is the contact process, 

 in which the sulphur dioxide gas, in the presence of so-called 

 catalytic substances (platinum sponge, platinized asbestos, 

 iron oxide, etc.) is directly oxidized to sulphur trioxide (SO3), 

 which is then absorbed in water to form sulphuric acid of any 

 degree of strength. Recently it has been found more econom- 

 ical in making sulphuric acid to utilize the sulphide minerals 

 as the source of sulphur dioxide gas. In this manner the more 

 costly brimstone is reserved for purposes other than acid 

 manufacture, and for which the sulphide minerals would not 

 be applicable. 



The use of pyrite as a raw material in the manufacture 

 of sulphuric acid was first proposed by an Englishman named 

 Hill, who obtained a patent for the process in 1818. It was 

 not until 1838, however, when the price of crude sulphur was 



