Patent GB-435839-A (GB)
Title: Improvements in and relating to the separation of mixtures comprising watersoluble amino acids and ammonium sulphate
IPC: C01C1/24
Filed: 1935-01-10
Abstract: The separation of amino-acids from their mixtures with ammonium sulphate is effected (1) by saturating an aqueous mother lye containing them, with ammonia, separating the precipitated ammonium sulphate, and removing the free ammonia, adding a mixture of amino-acid and ammonium sulphate to the filtrate, separating the precipitated amino-acid, and returning the mother lye to the process, or (2) by introducing into a mother lye containing ammonium sulphate and amino-acid, a solution of the bisulphates of amino-acid and ammonium, such as is obtained in the hydrolysis of an amino-nitrile, then saturating with ammonia, removing precipitated ammonium sulphate, distilling off free ammonia and the added water, separating the precipitated amino-acid, and returning the mother lye to the process.  In the addition of a fresh mixture of amino-acid and ammonium sulphate to a filtrate freed from precipitated ammonium sulphate, according to the former process, if aqueous mixture is added, the original volume is restored by evaporation, or if solid mixture is added, the original volume is restored by addition of water.  According to examples: (1) a mixture of equal weights of glycine and ammonium sulphate is separated by alternately saturating with ammonia to precipitate ammonium sulphate, and adding fresh mixture with restoring the bulk of solution, to precipitate amino-acid, the precipitation of ammonium sulphate being carried out at lower, and of amino-acid at higher, temperatures, if desired; and (2) a solution containing glycine and ammonium sulphate is mixed with introduction of ammonia, with a solution of the mixed bisulphates, the ammonium sulphate filtered off; and the solution evaporated and cooled to precipitate glycine, to a point at which the remaining ammonium sulphate is still in solution.  The precipitates are washed and re-crystallized if desired, and the mother lyes for returning to the process may be purified with carbon, or evaporated and separated from the impure syrupy residue.ALSO:The separation of ammonium sulphate from its mixture with amino-acids such as are obtained by the hydrolysis of amino-nitrites, with sulphuric acid, is effected (1) by saturating an aqueous mother lye containing them, with ammonia, separating the precipitated ammonium sulphate, removing the free ammonia, adding a fresh mixture of ammonium sulphate and amino-acid to the filtrate, separating the precipitated amino-acid and returning the mother lye to the process, or (2) by introducing, into a mother lye containing ammonium sulphate and amino-acid, a solution of the bisulphates of amino acid and ammonium, such as is obtained initially in the hydrolysis of amino-nitriles, then saturating with ammonia, removing precipitated ammonium sulphate, distilling off free ammonia, and the added water, separating the precipitated amino-acid, and returning the mother lye to the process. In the addition of a fresh mixture of amino-acid and ammonium sulphate to a filtrate freed from precipitated ammonium sulphate, according to the first part of the process, if aqueous mixture is added, the original volume is restored by evaporation, or if solid mixture is added the original volume is restored by addition of water.  Examples are given of the separation of mixtures of ammonium sulphate and glycine by each method.