XVII 



SULPHUR AND ITS COMPOUND 



253 



EXPT. 262. The flask which contained the copper and 

 sulphuric acid should next be examined. It will be observed 

 that most of the copper has disappeared, and the contents of 

 the flask have a black colour. Add some water, shake well, 

 and filter, when a blue liquid is obtained. Evaporate this 

 partially, and put aside to crystallise. It will be found that 

 blue crystals are so obtained. 



These crystals are what are known commercially as blue vitriol, 

 the chemical name being sulphate of copper. We may therefore 

 state that Copper and sulphuric acid produce sulphur dioxide 

 and copper sulphate. 



Sulphur Trioxide and Sulphuric Acid. Although sulphur 

 dioxide does not burn, yet by suitable means we can make it 



Current of 'Qxygfy 



FIG. 129. Preparation of Sulphur Trioxide. 



combine with more oxygen and produce a higher oxide, which is 

 known as sulphur trioxide. 



EXPT. 263. In the tube AB place some platinised asbestos, 1 

 and pass through the tube a well-dried mixture of sulphur 

 dioxide and oxygen or air, the gases then being had into the 

 cooled tube D. Heat the tube of asbestos, and note that 

 white fumes are formed which condense in the cooler flask to 

 form a white powder or crystals. 



This powder is sulphur trioxide, and we may now state : 

 Sulphur dioxide with oxygen forms sulphur trioxide. 



1 This is prepared by dipping asbestos fibres into (1) platinic chloride solution, (2) 

 ammonium chloride solution, and heating strongly. By this means the asbestos 

 becomes coated with a quantity of very finely divided platinum. 



