The properties of the most important zirconium compounds are correlated to the main ceramic applications of these compounds, namely, refractories, ceramic bodies, binders, cements, glazes, glasses, and enamels. A brief survey of the information available on the systems MgO-ZrOz, TiOz-ZrOz, SiOa-NazO-ZrOz, and several other systems is included. The more specific ceramic properties are summarized in short descriptions of the applications to each single ceramic field. The ceramic uses of thorium oxide are listed.* Cited by Biissem, reference 10. Vol. 25, No. 5 zirconia, 66@) were suggested in England. 65(") Bibliography A. I. Andrews and R. W. Gates, "Solubility of ZrO2 Opacifier in Enamel Glasses," Jour. Amer. Ceram. Soc., 23 [lo] 288-90 (1940). J. d'Ans and J. Loffler, "Studies on System NaD-Si02-Zr02," 2. anorg. allgem. Chem., 191 [I] 1-35 (1930); Cerum. Abs.. 9 [ll] 985 (1930); see also J. Loffler, reference 45. ABSTRACTIn combination with neodymium oxide, which compensates the remaining hue, it represents the ideal decolorizer. Cerium oxide absorbs in the ultraviolet without affecting visible transmission. It is used as an enamel opacifier in France, Various other applications of the rare earths are listed, including those which are based on the abrupt division of the visible spectrum by the sharp absorption band of neodymium in the green.