PRODUCTION OF INDIUM OXIDE

PURPOSE: To provide a production method in which a high purity inorg. acid indium soln. is produced from an indium-containing matter, for example, from indium oxide tin scrap material, etc., and high purity iudium oxide is produced from this soln. in high yield at low cost. CONSTITUTION: The production method of the indium oxide is composed of the first process in which the indium-containing matter is leached with nitric acid to obtain a indium nitride soln., the second process in which an indium ion is extracted from the soln. obtained at the first process by using an alkylphosphate based extraction agent, and the obtained extracted liq. is inversely extracted with inorg. acid to obtain the indium soln., the third process in which the indium ion is extracted from the soln. obtained at the second process by using a carboxylic acid based extraction agent, and the obtained extracted liq. is inversely extracted with the inorg. acid to obtain the indium soln. and the fourth process in which the soln. obtained at the third process is allowed to react with alkali and an obtained indium hydroxide is calcined to obtain the indium oxide.