SULPHUR AND PYRITE 349 



the temperature is still further raised, the substance, while re- 

 taining its dark color, again becomes liquid, although it does 

 not regain its former limpidity. At 448° C. the liquor boils 

 and is converted into a pale yellowish brow^n colored vapor. 

 In cooling the same changes occur in reverse order. The at- 

 omic weight is 32. The specific gravity of ordinary octa- 

 hedral sulphur is 2.05; of prismatic sulphur, 1.96. 



Sulphur is used in the preparation of sulphuric acid, in 

 the manufacture of gunpowder, in making friction matches, 

 in vulcanizing rubber, as an insecticide, and in medicine as 

 a laxative and for certain skin diseases. 



Sulphur occurs in combination with other elements, form- 

 ing the large and important groups of minerals, the sulphides 

 and the sulphates. Of the sulphide minerals, the combinations 

 with the metallic elements are of primary industrial impor- 

 tance, and, with the possible exception of the iron sulphides, 

 they form the ores from which many of the base metals are 

 obtained. 



Sulphur dioxide (SO3) is the direct combination of sul- 

 phur with oxygen and is found naturally as a minor constituent 

 of the atmosphere, particularly near volcanoes, and over large 

 cities, where its presence is due to the oxidation of the sulphur 

 contained in the fuel burned. 



In vegetables sulphur exists in some of the tissues of 

 plants, although not in the woody tissues. In animals it con- 

 stitutes an essential element of the blood, muscles, skin, hair 

 and other parts. 



Hydrogen sulphide (HgS) and sulphur dioxide (SO2) are 

 evolved from volcanoes as gases, which are doubtless the pro- 

 ducts of the action of the water of the ocean which has pene- 

 trated to the interior of the volcano upon the molten metallic 

 sulphides that exist there. 



The two forms in which the sulphur is marketed are the 

 flour, or flowers, of sulphur, which is a light powdery form of 

 the substance caused by the condensation of sulphur vapor; 

 and brimstone, or sulphur, which is made usually by melting 

 this soft powder and molding the liquid thus obtained into 

 large blocks or cylindrical rods in wooden molds. 



Natural deposits of sulphur are sometimes found strati- 



