2 ART. 16.— EDWARD DIVERS. 



sulphate or ferric or ferrous sulphate has been previously dissolved in 



the acid. Lastly, certain metals and other substances serve to 



produce this colour, or a modification of it, by acting on nitrososul- 



phuric acid in monohydrated sulphuric acid, among them being finely 



divided copper, silver, or mercury. Sabatier has not isolated the 



substance which gives this violet colour to sulphuric acid treated by the 



foregoing processes, but has suggested that it my be the unknown 



acid of Fremy's sulphazilaie, which he renames nitrosodisulphonic acid. 



Kow, in the preceding paper on peroxylaminesulphonates, Haga 



has adduced reasons for doubting- the correctness of Sabatier's sugges- 

 ts oo 



tion that the bluish-violet acid is sulphazilic acid, that is, perox}^- 

 aminesulphonic acid. There is also one consideration which, although 

 not mentioned by Haga, may nevertheless have affected his judgment. 

 This is the fact that a substance which according to Haga's most 

 conclusive evidence, must be a peroxide, should be produced in the 

 ways prescribed by Sabatier. But this difficulty and those raised by 

 Haga all seem to disappear when the changes which give rise 

 to the acid and the very different conditions for the production of the 

 salt and of the acid are all more closely examined, and leave nothing 

 in the way of accepting the view that this acid is peroxylaminesul- 

 phonic acid. 



The fact that the violet acid is dissolved in sulphuric acid, 

 whereas the violet salt is in aqueous solution, has to be taken into 

 account when the differences in the behaviour of the two are under 

 consideration, ft will then be seen that these differences are really 

 not greater than those between a sulphuric acid solution of nitrous 

 acid (as nitrososulphuric acid) and an aqueous solution of potassium 

 nitrite. The latter when acidified and I lie, former when diluted both 

 quickly lose most of the nitrous acid, there being no stable existence 

 of this acid in the intermediate conditions. Potassium nitrite is 



