Method of preparing an aqueous solid particle dispersion of a photographically useful compound.

摘要

A method of preparing of fine, stable, homogeneous and reproducible silica particle dispersions of a photographically useful compound, to be incorporated before or during the coating procedure into at least one hydrophilic layer of a photographic material on at least one side of a support comprising the steps of dissolving a non-watersoluble but alkali-soluble compound in an aqueous alkaline solution, if necessary with the help of an organic water soluble solvent; precipitating the said compound from said solution in the presence of colloidal silica sol , preferably in the further presence of a dispersing agent by lowering the pH of the solution; removing water-soluble salts formed by the precipitation and any organic solvent used and concentrating the dispersion either during or after the precipitation by dialysis or ultrafiltration or after precipitation by flocculation and decantation, followed by washing and further decantation.