Determination of sulphuric acid in alkylbenzene sulphonic acids

2 Determination of sulphuric acid in alkylbenzene sulphonic acids 

The method described by Sak-Bosnar et al. [10] depends on the fact that the second hydrogen ion of sulphuric acid is significantly weaker than the first, and than the hydrogen ion of alkylbenzene sulphonic acid (and others). It is therefore possible to determine sulphuric acid in alkylben- 

Dissolve about 0.2 g of the mixed acids in 25 ml of a 1 1 mixture of acetonitrile (caution toxic) and ethylene glycol. 

Titrate potentiometrically through two end-points with 0.1 M triethyla-mine in methanol, with continuous stirring. 

The mixed solvent was clearly the best of seven that were evaluated, and tolerates up to 10% water with only slight deterioration in the sharpness of the end-points. 

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