SULPHUR. 217 



which may be easily formed by burning sulphur 

 in oxygen gas. Now, when we convert oxygen 

 gas into sulphurous acid by this process, we do 

 not produce any alteration in its volume, but we 

 produce an increase in its specific gravity. 

 Hence, it is obvious that, if from the specific 

 gravity of sulphurous acid gas we subtract the 

 specific gravity of oxygen gas, the remainder will 

 give us the weight of sulphur united to a volume 

 of oxygen gas. I have shown in a paper on the 

 Specific Gravity of the Gases, inserted in the 16th 

 volume of the Annals of Philosophy, (p. 256) 

 that the true specific gravity of sulphurous acid 

 is '2222* ; and we have seen that oxygen gas 

 weighs 1-1 111. Hence, it is obvious that sul- 

 phurous acid is composed of 



Sulphur 1-1 111 

 Oxygen 1-1 11 1 



2-2222* 



Or of equal weights of each constituent. We 

 may consider sulphurous acid gas as a compound 

 of 



1 volume oxygen gas 1 



, V condensed into 1 volume. 



1 volume sulphur vapour ) 



3. Sulphuretted hydrogen gas may be obtained c 

 by mixing together sulphuret of antimony and pi 

 muriatic acid in a small retort, and applying the ^ 

 heat of a lamp. The gas may be collected over 





