Process for the production and / or purification of the salt of compound (S) -2- [4- (2- fluorobenzyloxy) benzylamino] propanamide ralfinamide (Ia), ** Formula ** ralfinamide (Ia) or the respective R enantiomer (I'a), with methanesulfonic acid in the form of the crystalline anhydrous polymorph identified as form A, which has an X-ray powder diffraction pattern (PXRD) that has essentially characteristic peaks expressed in grades 2q a: 6.93； 7.80； 9.66； 11.38； 12.04； 13.02； 13.82； 15.60； 16.36； 16.62； 17.52； 17.83； 18.75； 19.35； 19.70； 20.34； 20.69； 21.20； 22.69； 22.95； 23.23； 23.50； 24.80； 25.24； 25.8056； 26.01； 27.84； 28.07； 28.55； 29.16； 29.82； 30.77； 31.50； 31.95； 32.38； 33.37； 33.96； 34.61； 34.95； 36.02； 36.46； 37.38； 38.04； 39.66, in which the content of each of the impurities having a genotoxic effect, consisting of one or more (C1-C5) alkyl methanesulfonate (s), is less than 0.05 ppm, and of each one of the residual solvents known as potential precursors thereof, which consist of one or more alkanol (s) (C1-C5) or ester (s) thereof with lower alkanoic acid (s), it is less than 6 ppm, characterized in that: (i) the salt is produced or purified by crystallization from a solution in a solvent selected from: a) water, b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and c) acetone, an aliphatic ketone of 4-5 carbon atoms, or a mixture thereof； or (ii) the solid salt that contains an unwanted amount of impurities that have a genotoxic effect and / or of the residual solvents known as potential precursors thereof, is suspended with a solvent selected from: (a) water, ( b) a mixture of water with acetone or an aliphatic ketone of 4-5 carbon atoms, and (c) acetone, an aliphatic ketone of 4-5 carbon atoms, or a mixture thereof； or (iii) the solid salt, which contains an unwanted amount of impurities that have a genotoxic effect and / or of the residual solvents known as potential precursors thereof, is exposed to an air stream that has a h
