Sb(III) in microconcentrations forms a colloid only to a low extent due to hydrolysis and to adsorption on impurities incidentally present in solution. Sb(III) in microconcentration is less hydrolysed than in macroconcentration. In macroconcentration deeper hydrolysis of Sb(III) leads to the formation of its colloidal basic salt or hydroxide. In microconcentration at pH = 3 the colloid of Tl(III) consists essentially of impurities with adsorbed Tl(III) ; at higher pS. values by thallium hydroxide. In macroconcentration larger and better centrifugable particles of Tl(III)hydroxide are formed than in microconcentration.