The Colorimetric Estimation of Gitoxigenin in Presence of Digitoxigenin

Abstract

Summary A new reagent, consisting of a mixture of concentrated sulphuric acid, syrupy phosphoric acid and ferric chloride is recommended for the colorimetric estimation of gitoxigenin in presence of digitoxigenin. Various experiments showed that the most favourable results are achieved if the composition is the following:—concentrated sulphuric acid, 37·5 per cent, w/w; syrupy phosphoric acid (85 per cent.), 62·5 per cent. w/w; and hydrated ferric chloride, 0·050 per cent. w/w. The red colour originating from the interaction of this reagent with gitoxigenin must be measured at 5750 Å. The extinction of the colour obtained with gitoxigenin is approximately 80 times as great as that of an equal quantity of digitoxigenin and keeps a constant value for at least 2 hours.