1820.] Specific Graviti/ of Gases. 259 



But it is impossible that his experiments, how carefully soever 

 made, can ever give him the exact truth, because the data which 

 he consta^itly employs in all his calculations are inaccurate in 

 several particulars. For example, he considers sulphate of 

 barytes as a compound of 



Sulphuric acid 33'o 



Barytes 66-5 



100-0 

 ^Vhereas its real composition is 



Sulphuric acid. . . .' 33-89831 



Barytes 66-iqi69 



100-00000 

 But if sulphuric acid be a compound of 



Sulphur 100 



Oxygen 150 



Then sulphurous acid is a compound of 



Sulphur 100 



Oxygen 100 



Consequently the specific gravity of vapour of sulphur and ot 

 oxygen gas are the same, and the true specific gravity of sul- 

 phurous acid gas is 2-2222. 



We are acquainted with three combinations of sulphur and 

 oxygen ; namely, hyposulphurous acid, sulphurous acid, and 

 sulphuric acid ; the composition of which is as follows : 



Sulphur. Oxygen. 



Hyposulphurous acid 100 + 50 



Sulphurous acid 100 + 100 



Sulphuric acid 100 + 150 



No one who considers these compounds can hesitate to conclude 

 that hyposulphurous acid is a compound of one atom sulphur + 

 one atom oxygen ; sulphurous acid of one atom sulphar + tv/o 

 atoms oxygen ; and sulphuric acid of one atom sulphur + three 

 atoms oxygen. Hence it follows that the atom of sulphur is 

 twice as heavy as the atom of oxygen ; so that an atom of 

 sulphur weighs 2. Now 2 is a multiple of 0-125, the atom of 

 hydrogen; for 0*125 x 16 = 2. 



If we reckon the specific gravity of oxygen gas unity, then 

 the specific gravity of the vapour of sulphur will be 1 ; and 1 x 

 2=2. We see then that the weight of an atom of sulphur is 

 just twice the specific gravity of its vapour, as is the case with 

 so many other bodies. 



2. Su/pfturetted Hj/drogen. — This gas may be obtained pure 



r2 



