The second ortho­rhom­bic polymorph of zwitterionic metanilic acid at 130 K.

The low-temperature (130 K) crystal structure of the second ortho­rhom­bic polymorph of metanilic acid (3-amino­benzene­sulfonic acid), C6H7NO3S, shows the presence of two independent and conformationally similar mol­ecules of the zwitterionic acid (3-ammoniobenzenesulfonate) in the asymmetric unit; these inter­act through hydrogen bonding to give a cyclic R22(14) association. Peripheral hydrogen bonding gives a three-dimensional framework polymer, such as was found in the earlier polymorph [Hall & Maslen (1965), Acta Cryst. 18, 301–306], but the overall structural make-up is significantly different. [ABSTRACT FROM AUTHOR]