Abstract
Biphenyl-4,4'-dicarb-oxy-lic acid was recrystallized from N,N-dimethyl-formamide (DMF) yielding the title compound, C(14)H(10)O(4)·2C(3)H(7)NO. The acid mol-ecules are located on crystallographic centres of inversion and are hydrogen bonded to DMF mol-ecules. These hydrogen-bonded units form infinite chains although there is no inter-action between the methyl groups of neighboring DMF mol-ecules.