Quantitative Analysis of Azo and other Dyes and Intermediates

Abstract

An oxidative method of semi‐micro analysis suitable for nitrogen in dyes is described. The results with a representative number of different types of azo dye and some members of other classes agree closely, for the majority of the dyes examined, with those obtained by titanous chloride analysis, and the new method has the advantage of being simple, rapid, and clean in use. The procedure involves measurement of the volume of nitrogen produced on boiling the dye with a dilute solution of potassium dichromate and sulphuric acid. A still simpler, colorimetric method of determining water‐soluble azo dyes uses ceric, sulphate oxidation. It is useful for some dyes, but many do not react in simple proportion with the oxidant. A colorimetric method for the determination of the purity of coupling components for azo dyes is also described. This procedure is simpler than the usual method of diazo titration.