Sertraline acid addition salt, its preparation and its use in the preparation of sertraline hydrochloride form II

A process for preparing sertraline hydrochloride Form II which comprises (a) slurrying a sertraline acid salt wherein the acid is selected from phthalic acid, glutamic acid, adipic acid, salicylic acid, 4-methyl benzoic acid, 4-methoxy benzoic acid and (R)-mandelic acid in an organic solvent or organic solvent mixture at a temperature between ambient temperature and the boiling point of the solvent or solvent mixture, preferably between 25 and 80° C. (b) treating the slurry with a source of hydrochloric acid and (c) stirring the mixture obtained between ambient temperature and the boiling point of the solvent or solvent mixture for a period of time sufficient to effect the transformation to sertraline hydrochloride Form II.