Abstract
A method was devised whereby a minute amount of α-crocin contained in the crocus could be rapidly and correctly determined by the use of the Leitz-Rouy photometer. One mg. of pure α-crocin was dissolved in water to make 100cc. of a solution, placed in an absorption tube by the usual method, and a standard graph was drawn up from the indications of the galvanometer, using 415mμ filter. Next, 0.05% solution of potassium dichromate was prepared and its standard graph prepared. It was found that the standard curve of the dichromate solution above 50γ concentration was found to be parallel to that of α-crocin curve (cf. Fig. I). It follows, therefore, that the standard curve prepared with potassium dichromate solution could be used in place of α-crocin. The relationship between the two could be calculated from the following equation:
α-Crocin (in γ)=K2Cr2O7(inγ)/50+0.7
where 0.7 denotes a constant when the Leitz-Rouy photometer is employed with a filter of 415mμ. An aqueous extract of crocus powder is used for the determination of α-crocin.
