300 E. DIVERS AND ï. HAGA : 



is stopped, owing to sulplionatiou of the nitrite and reconversion 

 of acid carbonate to normal carbonate — - 



]S[aNO, + 2Na2S03 + 3NaHC03=Na2HNS20, + 3Na2C03+H20. 

 such a mode of sulphonation will therefore be also in operation 

 when the entrance of more sulphur dioxide has not been arrested, 

 but it is very slow in presence of normal carbonate and may- 

 be disregarded as a factor in the process of sulphonating when 

 sulphur dioxide is also at work. Here we would insert that only 

 to simplify discussion do we speak of normal sulphite and carbon 

 dioxide, or even acid carbonate, being together unchanged ; these 

 substances, as previously stated, act on each other to a large 

 extent in ice-cold solutions, and in uur work we met with pre- 

 cipitated acid-carbonate at times when it could only be there in con- 

 sequence of carbonic acid withholding sodium from pyrosulphite. 

 That in the earlier stages of the process, when much 

 carbonate is present, the normal sulphite plays a very small part 

 ill the sulphonation not only follows from the observation of its 

 rapid increase in quantity at first but is also shown by its then 

 nearly constant quantity for a long time though sulphur dioxide 

 is still entering the solution and forming sulphonates. Only 

 later, as the carbonate gets consumed, does the sulphite become 

 an important factor in the sulphonation by freely becoming pyro- 

 sulphite, for then its quantity rapidly falls. 



The part played by sulphite in the early stages being thus 

 insignificant, we have to seek in the carbonates the source of the 

 early considerable sulphonation of the nitrite. It would be un- 

 reasonable to assume, with acid carbonate present, that the normal 

 carbonate takes part in sulpnonation ; equally so to assume that 

 it remains inactive to sulphur dioxide. We are therefore com- 

 pelled to recognise that sulphonation goes on only after con ver- 



