Abstract: In 0.2 mol L~(-1)acetate buffer Solution, at pH 4.2—4.5, carminic acid exhibits a reversible adsorptive wave in single-sweep polarogram. The electrode reaction is
(H_2L~(-))_(ads)+2H~++2e<=>(H_2L′~-)_(ads)
H_2L~- and H_2L′~(-) are the anthraqluinone and dihydroanthraquinone ions of carminic acid respectively.
On the surface of mercury electrode,the adsorption of carminic acid obeys Frumkin adsorption isotherm The adsorption coefficient(β=7.0×10~6), the interaction factor(v=-0.92), the amount of saturated adsorption (Γ_s=1.39×10~(-10) mol cm~(-2) and t...