Ammonium oxalate monohydrate is a diammonium salt of oxalic acid. Its refined crystal structure has been investigated by three-dimensional diffraction studies. Influence of bivalent [Mn(II), Co(II), Ni(II)] and trivalent cations [Fe(III), Cr(III)] impurities on the growth rates of ammonium oxalate monohydrate crystals has been described. Its space group and unit cell parameters have been analyzed by neutron diffraction studies. Its IR spectra have been compared with that of isolated coal-solubilizing agent (CSA).