Abstract
A pH dependence of absorption spectra of carthamin in aqueous solution was investigated by the principal
component method. In aqueous solution near to neutral condition, the spectral change showed the existence of two components, A and B, the maximum absorption of which were at 520 and 500 nm, respectively. They seemed to correspond to F0 and Fx0 in silk cloth dyed from the neutral dye bath, as reported previously. The following equilibrium was set up between the components of A and B : A<-> B + H+ (.log K = 6.9). In acidic conditions, a small amount of the third component existed. On the other hand, the other components (D and D') existed in alkaline conditions. On the basis of the examination results, the acid-base equilibriums between these components were supposed, and the chemical species having different number of dissociated hydroxyl groups of carthamin were tentatively assigned to these components.
