0 1 2 3 4 5 DISTANCE FROM HOT FACE (IN.) Fig. 18. Distribution of lime plus silica after slogging.

The electrical conductivity of Mz03-Zr02 compositions containing 6 to 24 mole yo M@3, where M represents La, Sm, Y, Yb, or Sc, was examined. Only Sm%Os, Yz03, and Ybz03 formed cubic solid solutions with ZrOz over most of this substitutional range. Scandia forms a wide cubic solid solution region with Z r 0 2 at temperatures above 130OOC whereas the cubic solid solution region at room temperature is narrow (6 to 8 mole % Sc203). Lanthana additions to Zr02 produced no fluorite-type cubic solid solutions within t h e compositional range investigated. Generally, the electrical conductivity of these cubic solid solutions increased a s t h e size of t h e substituted cation decreased and the electrical conductivity for each binary system attained a maximum at about 10 to 12 mole ' % M&.

An X-ray diffractometer method similar to one used to determine the crystallinity of stretched rubber has been applied to partly devitrified glass. Percent crystallinity is equated to lOO(1, -I,)/ ( I , -ID). Ig, I,, and IB are respectively the noncrystalline scattering intensities measured at a single value of 28 for the parent glass (zero crystallinity), the partly devitrified glass, and a mechanical mixture of crystalline compounds chemically equivalent to the parent glass. The value of 26' is selected such that the noncrystalline scattering is high for the parent glass and at the same time is free of crystalline scattering in the case of the partly devitrified glass and of the mechanical mixture. The assumptions and approximations inherent in the method are discussed and their validity is tested. The method is rapid, virtually independent of the crystalline species present, and accurate to * 5 % or better.

Subsolidus equilibrium relations in a portion of the system Li20-Fe203-A1203 in the temperature range 500' to 14OO0C. have been determined near pol = 0.21. Of particular interest in this system is the LiFes08-LiA1508 join, which shows complete solid solution above 1180'C. Below this temperature the solid solution exsolves into two spinel phases. At 6OO0C. approximately 15 mole ' % of each compound is soluble in the other. The high-temperature solid solution and the low-temperature exsolution dome extend into the ternary system from the 1:s join. There is no appreciable crystalline solubility of LiFe02 or of a-Fe203 in LiFe508. An attempt to confirm H F e 5 a as the correct formulation of the magnetic ferric oxide "y-Fe203" was inconclusive, but in the absence of positive evidence, the retention of -y-Fe203 is recommended. All the metallic oxides of the Group IV elements increase the temperature of the monotropic conversion of y-Fez03 to a-Fe203. Silica and thoria have a greater effect on this conversion than does titania or zirconia.

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