The asymmetric unit of the title compound contains one (S)-1-phenyleth
ylammonium cation, one (S)-mandelate anion and two (S)-mandelic acid m
olecules. The entities are connected by an extensive hydrogen-bond sys
tem. The crystal structure is very similar to that of its diastereomer
ic less soluble compound (R)-1-phenylethylammonium (S)-mandelate-mande
lic acid (1/2).