The determination of carbazole in anthracene

Abstract

Anthracene used in certain industrial processes must be substantially free from carbazole. No simple method, suitable for the routine determination of the carbazole content of semi-refined and refined technical anthracenes -containing up to about 6 yo and less than 1 yo carbazole respectivelyappears to be available in the literature. An investigation which ultimately led to the development of a suitable method was accordingly undertaken. The results are summarised in the present paper. E x p e r i m e n t a1.From the practical point of view it was considered desirable to devise a method which would be applicable without significant modification to semi-refined (up to about 6 % carbazole) and refined (less than 1 % carbazole) anthracenes, a consideration best met by a colorimetric procedure.A variety of qualitative colour reactions for carbazole is recorded in the literature, many of which use a relatively large proportion of concentrated sulphuric acid as condensing agent. This reagent is impracticable in the present case owing to its charring action on the large proportion of anthracene present. Attention was directed to the possibility of adapting one of these colour reactions to the quantitative determination of carbazole in anthracene using, where possible, condensing agents other than sulphuric acid or alternatively minimum quantities of suitably diluted sulphuric acid.