Cerium oxide (CeO) is an oxide of the rare earth element Cerium. It is primarily utilized by the glass industry and is manufactured for various applications. In optical and other glass production, it is employed as a polish and can be used as a substitute for tin oxide in certain cases. In the production of cathode ray tubes (CRTs), cerium oxide serves a dual purpose as it is utilized as both an ingredient in the faceplate glass and as a polish in the finishing of the ware. Cerium oxide can also be used to decolorize glass by modifying the valance state of the iron contained in the glass. Furthermore, it finds applications as a catalyst substrate and is a component of the converter's oxidizing catalyst system used in automotive catalysts.