Time-dependent properties of colloidal dispersions of ferric-hydroxy polycations

The variation of pH, unpolymerised iron(III) concentration and optical density with time after preparation for colloidal dispersions of ferric-hydroxy polycations has been measured. Changes in these parameters are sensitive to the extent of hydrolysis of the Fe(III) ion while counter-ions and initial ferric ion concentration affect the stability of the dispersions with respect to the formation of hydrous oxide precipitates.