The solubilities of metal-surfactant salts in aqueous systems influence foam separation processes. The solubility products of selected salts of metal ions with anionic C-12 surfactants were determined. Lead dodecylsulfate, lead dodecylsulfonate, lead dodecanoate and chromium dodecylsulfate have solubility products of 1.9 x 10(-10), 5.0 x 10(-12), 4.4 x 10(-16) (mol dm(-3))(3), and 6.9 x 10(-14) (mol dm(-3))(4), respectively, as determined from turbidity measurements. Copper and cadmium dodecylsulfates have significantly higher solubility products of 3.79 x 10(-3) and 3.18 x 10(-2) (mol dm(-3))(3), respectively, determined by chemical analysis of supernatants produced after precipitation of the salts. (C) 1997 Published by Elsevier Science B.V.