Process of preparing a potassium stannate-stannic oxide sol tin electroplating solution

A process for the production of a stannic oxide sol-potassium stannate tin plating solution is disclosed comprising the steps of: anodically dissolving stannous tin in a potassium electrolyte such as potassium hydroxide to form potassium stannite in a first electrolytic cell including an anode compartment and a cathode compartment; simultaneously preventing the potassium stannite from migrating from the anode compartment to the cathode compartment by interposing therebetween a permselective ion exchange membrane (e.g., an anionic permselective membrane); oxidizing said potassium stannite to form a potassium stannate-containing solution by suitable means such as by contacting an oxygen-containing gas with the potassium stannite in a scrubbing tower; electrodialytically transferring potassium cations of said potassium stannate-containing solution from an anode compartment of a second electrolytic cell to a cathode compartment of said second electrolytic cell while simultaneously preventing migration of tin anions from said anode compartment to the cathode compartment by maintaining a cation permselective dialytic membrane between the anode and the cathode; and recovering a stannic oxide sol-potassium stannate solution from the anode compartment of said second electrolytic cell.