The analysis of two-dimensional condensation of organic compounds at the mercury/aqueous solution interface is carried out using a two-state Ising model formalism. Explicit results for the transition potential in terms of surface coverage, temperature and adsorbate concentration are reported. A methodology for estimating critical temperatures using the classical formula of dispersion forces is proposed, and the calculation of critical concentration is discussed. The estimated critical parameters are compared with the experimental data for various organic adsorbates.