Abstract
1) The first reaction given by dibasic acid of fatty series in the presence.of resorcinol and concentrated sulphuric acid, is a quite new one as to the fumaric acid.
Fumaric acid gives red-color with green fluorescence and by this color is distinguishable from succinic acid which gives just a green fluorescence by the same treatment.
The colourations given by malic, tartaric and citric acids distinguish them from each other most conveniently.
2) The color reaction given by α-naphtol and concentrated sulphuric acid (second reaction) is a new one for fumaric acid (green to red). Succinic acid shows less delicacy than fumaric acid. So it is most conveniently advisable to use this reaction for the identification of either fumaric or succinic acid, especially when the former is present in succinic acid as an impurity. Tartaric acid gives no fluorescence in the last colouration in this reaction as experienced in the first reaction. Citric acid may be distinguished from other acid only by the absence of fluorescence in the last colour.
3) Green colour with fluorescence given by fumaric acid in presence of β-naphtol and sulphuric acid is a new reaction as far as related to this acid. As to succinic, malic, tartaric and citric acids the colouration given by the same procedure is quite specific to each of these acids. The distinction of succinic acid from fumaric exists in the purplish tinge by the former in the stage of heating in the procedure. Both malic and tartaric acids distinguish from fumaric, succinic and citric acids by the fluorescent light yellow colouration in the end of the reaction. Malic acid characterizes itself from tartaric acid by a yellowish-red or a fluorescent yellow colour in the stage of heating and a red colour by the addition of water in the procedure i. e. the colouration due to the latter is dark bluish-green on heating and dark when diluted with water.
4) The fourth colour reaction given by fumaric acid in presence of hydroquinone and sulphuric acid is a new one with regard to this acid. By the same procedure succinic acid gives a fluorescent yellowish-green colouration which is easily recognisable even accompanied with yellow colour to be produced by fumaric acid if present as an impurity. Malic, tartaric and citric acids show a very delicate and characteristic colouration by this procedure.
