NATIVE SULPHUR. 99 



former kind are common in the state of New York, and of 

 the latter in the coal mines of Pennsylvania, the gold rocks 

 of Virginia and elsewhere. 



The sulphur of commerce is also largely obtained from 

 copper and iron pyrites, it being given off during the roasting 

 of these ores, and collected in chambers of brick work con- 

 nected with the reverberatory furnace. It is afterwards 

 purified by fusion and cast into sticks. 



Sulphur when cooled from fusion, or above 232° F., crys 

 tallizes in oblique rhombic prisms. When poured into 

 water at a temperature above 300 F. it acquires the consis 

 tency of soft wax, and is used to take impressions of gems, 

 medals, &c, which harden as the sulphur cools. 



The uses of sulphur for gunpowder, bleaching, the manu- 

 facture of sulphuric acid, and also in medicines, are well 

 known. Gunpowuer contains 9 to 20 per cent. — 9 or 10 

 per cent, for the best shooting powder, and 15 to 20 for 

 mining powder. 



SULPHURIC AND SULPHUROUS ACIDS. 



Sulphuric acid is occasionally met with around volcanoes, 

 and it is also formed from the decomposition of sulphureted 

 hydrogen about sulphur springs. It is intensely acid. Com- 

 position, sulphur, 40*14, oxygen 59*86. It is said to occur 

 in the waters of Rio Vinagro, South America ; also in Java, 

 and at Lake de Taal on Luzon in ihe East Indies; in Gen- 

 esee Co., N. Y. ; and at Tuscarora, St. Davids and else- 

 where, Canada West. 



Sulphurous acid is produced when sulphur burns, and 

 causes the odor perceived during the combustion. It is com- 

 mon about active volcanoes. It destroys life and extinguishes 

 combustion. Composition, sulphur 50"00, oxygen 49*00. 



Selenium, Arsenic. Selenium has close relations to sulphur. Its 

 most striking characteristic is the horse-radish odor perceived when it is 

 heated. It occurs in nature combined like sulphur with various metals, 

 and these ores, called seleniets or seleniurets, are at once distinguished 

 by the odor when subjected to the heat of the blowpipe flame. 



Arsenic is also near sulphur in a chemical point of view, although 

 metallic in luster. It forms similar compounds with the metals and 

 metallic oxyds, which are called arseniurets and are often highly im- 

 portant ores. The arseniurets of nickel and cobalt are the main sources 

 of these metals. Its ores are distinguished by giving off when heated 

 an odor resembling garlic. 



What is said of sulphuric acid 1 What is said of sulphurous acid? 



