Abstract: An improved process for preparing highly concentrated salt solutions of metals of high purity from waste metal sludges at superior dissolution rates is achieved by preparing, concentrating and washing the sludge containing insoluble metal hydroxide under specific conditions to safeguard against the solids being exposed to air or dried out. The wet sludge is then dissolved in a dilute acid. The resultant solution can be used directly e.g. as make up in many electrolytic metal finishing processes to compensate for drag out losses occurred, or as the primary metal source in electrolytic processes employing insoluble anodes. Other specific uses for the process include the preparation of aluminum sulfate coagulants.