The crystal structure of (+/-)-[2-[4-(2-hydroxyhexyloxy)phenylcarbamoyl]ethyl]dimethylsulfonium p-chlorobenzenesulfonate [(+/-)-SCC], which failed to effect preferential enrichment due to the chemical modification of the prototype (+/-)-[2-[4-(3-ethoxy-2- hydroxypropoxy)phenylcarbamoyl]ethyl]dimethylsulfonium p-chlorobenzenesulfonate [(+/-)-SC] showing preferential enrichment, has been determined by x-ray crystallographic analysis. The crystalline form of (+/-)-SCC is not a mixed crystal of the two enantiomers, but a racemic compound. In addition, the revised crystal structures of (+/-)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]ethyl] dimethylsulfonium p-toluenesulfonate [(+/-)-ST] and (+/-)-SC, both of which showed preferential enrichment, are described. The crystal structure of (+/-)-SCC is different from that of (+/-)-SC, but very similar to that of (+/-)-ST. The formation of the crystal phase of the (+/-)-SC type, which can be followed by polymorphic transition to afford the crystal one of (+/-)-ST type if necessary, seems to be essential for successful preferential enrichment.