Definition of colloidal sulfur
Amorphous sulfur in a finely divided condition. Prepared by the action of dilute sulfuric acid on sodium thiosulfate or by the reaction of hydrogen sulfide and sulfurous acid. Also prepared by mixing equivalent solutions of hydrogen sulfide and sulfur dioxide. Forms a clear yellow solution containing very minute suspended particles of sulfur; the addition of alum immediately precipitates the sulfur. Also called milk of sulfur.