An alternative procedure is described for producing diffraction-quality crystals of the sodium salt of the water-soluble porphyrin diaqua-5,10,15,20-tetra-p-phenylsulfonyporphinatocobalt(III), Na[Co(TPPS)(H2O)(2)]center dot 4H(2)O by vapour diffusion of ethyl acetate into an aqueous solution of the porphyrin overlaid with a layer of acetone. The structure contains a large amount of disordered solvent in channels but application of an appropriate algorithm (SQUEEZE - an algorithm incorporated into PLATON that applies a Fourier transform of the observed density in the solvent areas and incorporates its contribution to the structure factors) permits a structure solution. (C) 2012 Elsevier B. V. All rights reserved.