Eighteen maleanilic acids have been prepared by condensing various aromatic amines with maleic anhydride. Of these, thirteen have been studied for their use in the gravimetric analysis of zirconium. Maleanilic acids obtained from 2∶5-dichloroaniline, ortho and para toluidines, ortho and para-anisidines, 1- and 2-naphthylamines, meta-phenylenediamine and tolidine produced quantitative precipitation of zirconium, but the acids obtained from naphthylamines, m-phenylenediamine and tolidine proved very useful for the separation of zirconium from common cations. The ‘weighting effect’ played a significant role in the precipitation of this metal with maleanilic