ANALYSIS OF COMPLEX MATTER 



143 



of water surrounding the vessel in which the chemical change 

 takes place. The sulphur dioxide which is formed is, at 

 ordinary temperatures, a gas. The temperature of the sulphur 

 dioxide, when formed from its constituents, is always the same. 

 This is shown by the same quantities of sulphur and oxygen 

 always producing, on combination, the same thermal change 

 in the neighbouring body, water. 



The experiment may be roughly carried out in the following 

 manner : A vessel (A) is fitted with a cork containing three 

 holes. In one of these is fixed a tube conveying the oxygen ; 

 in another a long tube of thin copper, which is coiled several 



OXYGEN 



Fig. 49. 



times round the flask. This serves to carry away the sulphur 

 dioxide as it is formed, and bring about thermal equilibrium 

 between it and the water. It finally enters the aspirator B, 

 by which a slow stream of air or oxygen is drawn through the 

 vessel A. The third opening, in the centre, serves to introduce 

 the sulphur immediately the action is started, or this may be 

 done by touching the already fixed sulphur with a hot wire. 

 The oxygen used may be pure, or mixed with nitrogen, i.e. air 

 may be used. The numerical results will differ accordingly ; 

 but, in any case, the same quantity of sulphur, uniting with 

 oxygen under precisely the same conditions, will produce the 



