The quantitative estimation of certain beta-naphthol sulphonic acids singly and in presence of one another

Abstract

1. Crocein and G salts brominate extremely slowly in sulphuric acid solution, whereas Schaffer and R salts brominate readily.2. The addition of a large excess of potassium bromide previous to titration with bromate solution decreases the rate of bromination of Crocein salt.3. The temperature must not exceed 50 °, when titrat -' ing in hydrochloric acid solution, owing to dibromination of all four salts to a slight extent above 50°.4. Schäffer or /and R salt can be determined in the presence of Crocein or /and G salt by taking advantage of the different rates of bromination in sulphuric acid.5. The total sulphonate content of mixtures containing Schäffer or /and R salts and G salt can bedetermined.6. The total sulphonate content of mixtures contain ing Schäffer or R salt and Crocein salt can be determined (but not too satisfactorily).7. The accuracy of the methods described is about one per cent.