Abstract: A highly impact-resistant and corrosion-resistant material is used for an apparatus for use in hydrolysis of 2-hydroxy-4-methylthiobutanamide to obtain 2-hydroxy-4-methylthiobutanoic acid, said material being readily fabricated for an apparatus with a complicated structure and being an alloy which contains 16.0 to 22.0% by weight of a Cr element, 16.0 to 22.0% by weight of a Mo element, 1.0 to 2.5% by weight of a Ta element and a Ni element as the rest, an alloy which contains 26.0 to 32.0% by weight of a Mo element and a Ni element as the rest, or an alloy which contains 0.12 to 0.25% by weight of a Pd element and a Ti element as the rest.

Abstract: A method is provided of using a suitable material for an apparatus used in solid-liquid separation of a residue containing an inorganic salt, left to remain in an organic phase containing 2-hydroxy-4-methylthiobutanoic acid, the material being an alloy containing 21.0 to 30.0% by weight of a Cr element, 2.5 to 11.0% by weight of a Ni element, 1.0 to 5.0% by weight of a Mo element and a Fe element as the rest.

Abstract: A method is provided of using a highly impact-resistant and corrosion-resistant alloy material for an apparatus for use in hydration of 2-hydroxy-4-methylthiobutanenitrile to obtain 2-hydroxy-4-methylthiobutanamide, the material being readily fabricated for an apparatus with a complicated structure and being composed of an alloy which contains 16.0 to 22.0% by weight of a Cr element, 16.0 to 22.0% by weight of a Mo element, 1.0 to 2.5% by weight of a Ta element and a Ni element as the rest, or an alloy which contains 26.0 to 32.0% by weight of a Mo element and a Ni element as the rest.

Abstract: A process for producing methionine by hydrolysis of 5-(?-methylmercaptoethyl)hydantoin in the presence of an alkali, in which the concentration of hydrogen sulfide is 5 ppm or less in a solution used for hydrolysis comprising 5-(?-methylmercaptoethyl)hydantoin and the alkali, whereby methionine can be stably produced for a long period of time.

Abstract: In the process for producing methionine of the present invention uses, as an equipment material for a step of hydrolyzing 5-(?-methylmercaptoethyl)hydantoin in the presence of potassium carbonate to produce methionine, a stainless steel containing 21.0 to 30.0% by weight of a Cr element, 2.5 to 11.0% by weight of a Ni element and 1.0 to 5.0% by weight of a Mo element, a ratio of the total content of the Cr element and the Mo element to the content of the Ni element being from 4.7 to 14.0, is used.

Abstract: A process for producing methionine by hydrolysis of 5-(?-methylmercaptoethyl)hydantoin in the presence of an alkali, in which the concentration of hydrogen sulfide is 5 ppm or less in a solution used for hydrolysis comprising 5-(?-methylmercaptoethyl)hydantoin and the alkali, whereby methionine can be stably produced for a long period of time.

Abstract: In the process for producing methionine of the present invention uses, as an equipment material for a step of hydrolyzing 5-(?-methylmercaptoethyl)hydantoin in the presence of potassium carbonate to produce methionine, a stainless steel containing 21.0 to 30.0% by weight of a Cr element, 2.5 to 11.0% by weight of a Ni element and 1.0 to 5.0% by weight of a Mo element, a ratio of the total content of the Cr element and the Mo element to the content of the Ni element being from 4.7 to 14.0, is used.