Abstract: The present invention relates to a process for the production of dipotassium-ascorbate-2-sulfate-dihydrate, a vitamin C derivative. It is used, among other things, as an additive to fish feed. In the process according to the process according to the invention, trimethylamine-sulfur-trioxide complex is added in only slight molar excess to a concentrated solution of potassium-L-ascorbate in water, and the pH value of this reaction mixture is set by successive additions of potassium hydroxide at a value in the range between 9.5 and 10.5, and is kept at this value for the duration of the reaction. The process permits the profitable production of dipotassium-ascorbate-2-sulfate-dihydrate on a large industrial scale. It is also explained how trimethylamine-sulfur-trioxide complex can be recovered from trimethylamine which occurs as a by-product during the production of dipotassium-ascorbate-2-sulfate.

Abstract: In the process described for the production of sodium or potassium L-ascorbate, 2-keto-L-gulonic acid monhydrate is esterified with methanol. The esterification is only partial, that is, is not carried out until the esterification equilibrium is reached. In an intermediate step, by addition of sodium or potassium bicarbonate in an amount precisely enough for neutralizing the esterified solution, unesterified 2-keto-L-gulonic acid and impurities present are precipitated and separated out. Then by adding more bicarbonate, the lactonizing of the 2-keto-L-gulonic acid methyl ester formed is made possible. In order to reach a high yield, the unesterified 2-keto-L-gulonic acid from the bicarbonate precipitation may be re-esterified by the same process, preferably parallel, and also converted into ascorbate. This process makes possible the production of very pure sodium or potassium ascorbate, suitable for pharmaceutical purposes in a profitable way.