THE NONMETALLIC MINERALS. 181 



Extraction and 'preparation. Sulphur rarely occurs in nature in any 

 quantity sufficiently pure for commercial purposes. In freeing it from 

 its impurities three methods are employed: (1) Melting, (2) distillation, 

 and (3) solution. In the first the ore is simply dry washed at a low 

 temperature or treated with superheated steam until the sulphur melts 

 and runs off. Specimen No. 60861 shows the rock after being subjected 

 to this treatment. The first process is extremely wasteful; the second 

 much more economical in the end, but demanding a more expensive 

 plant. A process of fusion in a calcium chloride solution has come into 

 use of late years, and bids fair to yield better results than either of 

 the above. In the distillation process the ore is heated in iron retorts 

 until the sulphur distills off and is condensed in chambers prepared 

 for it. Specimen No. 60860 shows the rock after removal of the sulphur 

 by this process. The product is mostly in the form of "flower of 

 sulphur." The method is expensive, but the resultant sulphur very 

 pure. In the third process mentioned the ore is treated with carbon 

 disulphide, which dissolves out the sulphur and from which it is recov- 

 ered by evaporation. This method, while giving good results, is expen- 

 sive and spmewhat dangerous, owing to the explosive nature of the 

 gases formed. 1 



Uses. Sulphur is used mainly for making of sulphuric acid though 

 small amounts are utilized in the manufacture of matches for medici- 

 nal purposes, and in the making of gunpowder, fireworks, insecticides, 

 for vulcanizing india rubber, etc. In the manufacture of sulphuric 

 acid the sulphur is burned to sulphurous anhydride (SO 2 ) on a grate 

 and then conducted with a slight excess of air into large lead-lined 

 chambers and mixed with steam and nitrous fumes, where the SO 2 is 

 oxidized to the condition of SO 3 (sulphuric anhydride) and takes up 

 water from the steam forming H 2 SO t (sulphuric acid). Ordinary roll 

 sulphur is quoted in the current price lists at from 1 to 2 cents per 

 pound. (See also under iron pyrites, p. 190.) 



BIBLIOGRAPHY. 



R. PUMPELLY. Sulphur in Japan. 



Geological Researches in China, Mongolia, and Japan. Smithsonian Contri- 

 butions, XV, 1867, p. 11. 

 I. C. RUSSELL. Sulphur Deposits of Utah and Nevada. 



Transactions of the New York Academy of Science, I, 1882, p. 168. 

 A. FABER DU FAUR. The Sulphur Deposits of Southern Utah. 



Transactions of the American Institute Mining Engineers, XVI, 1887, p. 33. 

 The Sulphur Mines of Sicily. 



Engineering and Mining Journal, XL VI, 1888, p. 174. 

 V. LAMANTIA. Sulphur Mines of Sicily. 



U. S. Consular Report No. 108, 1889, pp. 146-155. 



1 The Mineral Industry, II, 1893, p. 600. 



