METHOD FOR PRECIPITATING CYSTINE

摘要

PROBLEM TO BE SOLVED: To provide a method for precipitating cystine which contains a residue of a sulfate of less than 300 ppm and satisfies the purity criteria according to food standards and pharmaceutical standards, from a sulfuric acid solution. SOLUTION: The method for precipitating cystine from a sulfuric acid solution is carried out as follows: Cystine precipitates are formed by charging a cystine solution in an aqueous sulfuric acid and an aqueous solution of a base concurrently into a mixing container. The charging is performed keeping the pH value is kept of the mixture in the container in the range of 1.0-7.0, and the temperature in the range from 30 deg.C to the boiling point of the mixture.