THE NON-METALLIC ELEMENTS: SULPHUR 67 



The non-metallic elements which have to be studied are 

 sulphur, chlorine, nitrogen, phosphorus, silicon, and carbon. 

 Of these, sulphur will first be considered. 



Place some sulphur in a dry test-tube, and heat, using a 

 test-tube holder. Note the melting of the sulphur and the 

 singular changes in the colour and viscosity of the liquid, till 

 the boiling point is reached. Note that the deep red vapour 

 ignites spontaneously as it issues from the tube, this tempera- 

 ture being high enough to promote rapid chemical combination 

 between the sulphur and the oxygen of the air, the sulphurous- 

 smelling oxide being formed. Pour the remaining liquid in a 

 thin stream into cold water, and note the plastic consistency 

 of the rapidly cooled sulphur. Dissolve some ordinary sulphur 

 in a little bisulphide of carbon, and allow the clear liquid to 

 evaporate spontaneously in a dish. Preserve the octahedral 

 crystals formed. Try to dissolve some of the plastic sulphur 

 in the bisulphide of carbon, and evaporate the liquid. Note 

 that no crystals are obtained, showing that plastic sulphur is 

 insoluble. This is an instance of allofropy, that is, the exist- 

 ence of an element in "another condition" having different 

 properties. 



Does sulphur, being a non-metallic element like oxygen 

 combine with metals and with hydrogen ? Mix together single 

 combining proportions of sulphur and iron filings (about 

 10 grams in all), place the mixture in a narrow test-tube, and 

 heat just the bottom of the test-tube strongly. Note that pre- 

 sently the contents of the tube begin to glow, heat being 

 obviously produced, thus showing that chemical combination 

 is occurring, and sulphide of iron is being formed. 



Sulphur is found in Sicily and other volcanic districts in the free state, 

 but it occurs more abundantly in nature combined with metals. Thus 

 galena, stibnite, cinnabar, iron pyrites, and zinc blende, are native sul- 

 phides of lead, antimony, mercury, iron, and zinc respectively. Copper 

 pyrites is a double sulphide of iron and copper. With the exception of iron 

 pyrites, all these ores are used as sources of the metals. 



