Abstract: The invention is directed to a method of making crystalline calcium ascorbate by reacting ascorbic acid and calcium carbonate in liquid water medium, using some excess of carbonate, at a temperature of not more than about 70.degree. C., under controlled conditions so that the reaction mixture is maintained saturated with carbon dioxide gas and a carbon dioxide foam blanket is maintained over the reaction mixture during the reaction time, said water being present in the reactor in an amount which provides a reaction product solution having a syrupy viscosity, and spontaneously crystallizing out of said syrup a mass consisting essentially of calcium ascorbate, which calcium ascorbate is a source of Vitamin C activity.