A systematic examination on the evolution of the morphology and size of barium oxalate hydrate (BaC2O4 center dot 0.5H(2)O) particles at room temperature in the presence of poly (sodium 4-styrene-sulfonate) (PSS) is presented. The results indicate that various parameters including the concentrations of both PSS and reactants, pH values and reaction time markedly influence the morphology and size of BaC2O4 center dot 0.5H(2)O. Small compact spheres, coral-like spheres, big fluffy spheres, dumbbell-like and flower-like crystals can be observed depending on the experimental conditions. It is found that PSS acts as an agent between the crystal and the positively charged ions. PSS can complex Ba2+, and further promote the nucleation and the crystallization by being attached to the specific facets of BaC2O4 center dot 0.5H(2)O, which finally results in diverse morphologies of BaC2O4 center dot 0.5H(2)O. (C) 2013 Elsevier B.V. All rights reserved.