1953 年 73 巻 7 号 p. 767-769
Intermediates of food coloring matter which are difficult to be obtained in a pure state by synthesis and are impossible to purify are R acid (2-naphthol-3, 6-disulfonic acid) and G acid (2-naphthol-6, 8-disulfonic acid). Their complete isolation was effected by a quantitative spot test using a round filter paper, and developing in a low-pressure, closed vessel, using acetic acid-butanol solution (butanol: water: acetic acid=5:4:1). The separated zones were cut out, extracted, and color developed by coupling with naphthionic diazonium solution in alkaline medium as Amaranth and New Coccine. These red dyes were colorimetrically determined by an electrophotometer. Amaranth, New Coccine, R acid, and G acid were purified by the chromatopile from which pure products of these were obtained. Quantitative spot test could be utilized for the quality tests and quantitative determination, rapidly and simply, for tar dyes used for food coloring, such as the Amaranth, New Coccine, Indigo carmine, and mixed dyes.