THE KINETICS OF THE CRYSTALLIZATION OF BARIUM CHROMATE IN PRESENCE OFPOLYPHOSPHATE AND PHOSPHONATES

The inhibiting effect of polyphosphate and phosphonates on the crystal lization of barium chromate for both seeded and unseeded systems has b een investigated using the changes in ionic conductivity of the lattic e ions in supersaturated solutions containing stoichiometric concentra tions of barium and chromate at 298 K. The inhibitors studied are sodi um tripolyphosphate (STP), ethylenediaminetetramethylenephosphonic aci d (ENTMP), and 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP). The e ffect of these inhibitors on the growth of crystals has been studied a t several inhibitor concentrations. The influence of these additives o n barium chromate crystallization could be interpreted in terms of a L angmuir type adsorption isotherm. The crystallization retarding effect due to inhibitors is in the order HEDP > STP > ENTMP. The inhibitors studied can be used as effective compounds for scale formation control .