A multi-parameter titration method for the determination of formation pH for metal hydroxides

pH values of metal hydroxide formation were determined at 23 degreesC using a new multi-parameter scanning instrument employing simultaneous turbidity , conductivity and pH measuring capabilities. Results suggest that a combin ation of data from several simultaneously measured parameters provides a mo re reliable basis for the generation of quantitative data regarding formati on pH and solubility, products of metal hydroxide precipitates than corresp onding values obtained from single parameter measurements. The advantage re sts in the possibility, to compare data from parallel sources as well as in the availability of characteristic information reflecting complementary as pects of the investigated systems. The present results obtained from alkaline titration of metal ion solutions coincide well with those found in literature, in particular when consideri ng the great disparity among published values. Mean pK(sp)-values determine d for 1, 5 and 10mM solutions of lead, cadmium, copper and zinc hydroxide a re 18.7, 14.4, 19.7 and 16.0, respectively. The pH(IEP) values of metal hydroxide precipitates were determined from. st oichiometric solutions to be 11.1, 10.0, 8.8 and 10.3 for Pb(OH)(2)(s), Cd( OH)(2)(s), CU(OH)(2)(s) and Zn(OH)(2)(s), respectively, by zeta potential m easurements. A dedicated instrument was used to measure the corresponding p article sizes, which corroborated with observations from the formation pH s tudies. (C) 2001 Elsevier Science Ltd. All rights reserved.