250 ELEMENTARY GENERAL SCIENCE CHAT-, 



sulphur." Sulphur is usually brought into commerce either in 

 this form or as long solid rolls, both forms being obtained 

 from a crude natural product which chiefly occurs, mixed with 

 mineral impurities, in the volcanic regions of Italy and Sicily. 

 The impure material is heated, and the melted sulphur is run 

 off from the earthy impurities. It is then again melted and 

 cast in cylindrical moulds to obtain the roll sulphur ; or, it is 

 strongly heated in retorts, so that it boils and the vapours are 

 allowed to condense in a large cooled chamber, where they collect 

 upon the walls and floor in the form of " flowers of sulphur." 



Sulphur also occurs naturally in the combined state, the most 

 important of its natural compounds being the sulphides, i.e., 

 compounds of sulphur with metals and many of these are 

 important ores, -i.e., are the natural compounds, from which we 

 obtain the metal itself for example, copper pyrites, galena or 

 lead sulphide, blende or zinc sulphide, &c. 



EXPT. 255. Heat a little iron pyrites in a test-tube. 

 Observe melted sulphur on the walls of the tube, and a 

 strong smell of sulphur dioxide. 



Crystalline Sulphur. Besides the two varieties of sulphur 

 we have already observed, we may obtain sulphur in the crys- 

 talline form by two different methods. 



EXPT. 256. Dissolve some sulphur in carbon disulphide 

 and allow the solvent to slowly evaporate. Examine the 

 crystals produced and sketch the most perfect. 



The crystals so obtained are 8-sided, and belong to what is 

 known as the rhombic system. The ordinary roll sulphur consists 

 of minute crystals of this form. 



EXPT. 257. Place some sulphur in an evaporating basin 

 and heat carefully. When all has melted allow it to cool 

 slowly, and as soon as a solid film has formed over the surface 

 quickly pierce two holes in it, and through one of them pour 

 out the interior liquid sulphur. Take up the top crust and 

 examine the mass, which will be found to consist of a number 

 of beautiful, needle-shaped, yellow, translucent crystals. 



The crystals thus obtained are quite different from those 

 produced in the previous experiment, and belong to what is 

 known as the monodinic system. 



