236 fV. Odling, Esq. [March 30, 



The compounds CI2SO, and ClgSOa, are obtainable from the chloro- 

 representative of sulphydric acid ClgS, by successive oxidation. The 

 first product actually afforded by the oxidation of sulphydric acid is 

 sulphurous acid HaSOg, which is produced by the combustion of sul- 

 phydric acid in air or oxygen. Conversely, sulphydric acid may be 

 obtained by deoxidating sulphurous acid with nascent hydrogen. 

 Sulphuric acid H2SO4, results from the oxidation of sulphurous 

 acid, and by deoxidation can reproduce that body, as in the ordinary 

 process for the preparation of sulphurous acid. Here then, includ- 

 ing the chloro-representatives, is a second series of acids associated 

 with one another by a common increment of composition, and by 

 mutual metamorphosis. 



Sulphuric acid H2SO4, is the representative on the sulphur series, of 

 perchloric acid HCIO4, on the chlorine series. Each contains one 

 atom of the radicle which gives the special character to the acid, in the 

 one case chlorine, in the other sulphur. Each contains also four 

 atoms, or volumes, of oxygen ; but whereas perchloric acid contains 

 only one atom, or volume, of hydrogen, sulphuric acid contains two 

 atoms, or two volumes. And this difference in composition leads to a 

 marked difference in the properties of the two acids. Perchloric acid 

 HCIO4, has only one atom of hydrogen that can be replaced. Hence it 

 forms only one description of salt, such, for instance, as perchlorate 

 of potassium KCIO4, and only one description of ether, such, for 

 instance as perchloric ether EtClOi. But sulphuric acid has two 

 hydrogen atoms that can be replaced. Hence it can form acid salts, 

 neutral salts, double salts, acid ethers, neutral ethers, double ethers, 

 and saline ethers, as shown in the table. 



Kg SO4 Sulphuric acid. 



KH 6O4 Acid sulphate of potassium. 



Kg SO4 Neutral sulphate of potassium. 



KNi SO4 Potassio-sulphate of nickel. 



EtH SO4 Ethylo-sulphuric acid. 



Eta SO4 Neutral sulphate of ethyl. 



EtMe SO4 Ethyl o-sulphate of methyl. 



EtK SO4 Ethylo-sulphate of potassium. 



This property «of forming acid and double salts, and acid and 

 double ethers, &c., indicates a fundamental difference in character be- 

 tween sulphuric and perchloric acids, a difference that is satisfactorily 

 represented by the difference in their formulae as here written 



