The present invention relates to 1-[2-(2,4-dimethylphenylsulfanyl)phenyl]piperazine acetate in crystalline form and to methods for the preparation thereof. In addition the present invention relates to solid pharmaceutical compositions for oral administration comprising an effective amount of the crystalline 1-[2-(2,4-dimethylphenylsulfanyl)phenyl]piperazine acetate. Moreover, the present invention relates to the use of crystalline 1-[2-(2,4-dimethylphenylsulfanyl)phenyl]piperazine acetate for the preparation of pharmaceutical compositions.