Equilibrium constant for calcium ion and ascorbate ion

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Abstract
The combination of calcium and ascorbic acid in water at 25°C has been examined by measuring the change of free calcium ion concentration as ascorbate was added in small increment to a solution of calcium. The data show clearly that complex formation between calcium ion and ascorbate ion occurred. At ionic strength μ=0.1–0.2, the equilibrium constant of Ca++ and the singly-charged ascorbate ion has been measured to be 2.1 M−1. The precision of the result is better than 5% and the accuracy is estimated to be better than 20%. The application of the equilibrium constants is discussed.