REVERSIBLE AND IRREVERSIBLE CHANGES IN HYDROGEN-ION TITRATION CURVES OF MELANINS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 11  (3) , 217-223
Abstract
H+ titration curves obtained on melanins prepared and modified differently show recognizable differences. Melanin prepared with NaOH exhibits irreversible loss of functional groups in the base range once titrated acidic. Melanin prepared with NH4OH shows 2 main branches selected by incubation at an extreme pH for 24 h. Longer exposure reveals other curves which disappear once a 24 h schedule of titration is resumed. The existence of 2 major pH branches appears consistent with the oxidation-reduction properties of melanins. These results demonstrate the ability to obtain a reproducible feature in the H+ titration curves, making it possible to quantitate CO2 adsorbed to melanin in solution at basic pH.

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