Electrical conductivities of some molten oxides have been determined. In order of decreasing equivalent conductances a t their melting points the oxides investigated were: LitO, I'bO, TeO?, Moo?, BitO3, V?Os, Sb,Oa, an! CrOS. The variation of the observed values of the s~e c~f i c conduct~vities. K. w~t h the absolute tern-, , perature, T, can be described b; an equation of the form,where A , B, C , etc. are constants. While the experimental data are adequately described by an equation of this form containing only the constants A and B, a sliahtlv better tit is obtained usinn three constants. The conductivities of the mzlten oxides follow a pattern of -variation from element to element which is substalltially the same as that of the molten halides. For elements giving more than one oxide stable in the molten state, the oxide corresponding to the highest state of valency has the lowest conductivity. Manzrscribt

HB kinetics and mechanism of the vaporization of lead oxide T from lead zirconate-lead titanate materials have been studied by Northrop.' This note indicates the nature of the changes in the electromechanical properties of lead zirconate-lead titanate d c s that result from a deficiency in lead oxide. The contents of this note are not in conflict with Northrop's findings but are submitted here as additional relevant information. A more extended account of this work will be published later.Consideration of the PbO-ZrOz-TiOa phase diagram'.' indicates that a loss of PbO a t constant Z a / T i G ratio should, for all compositions in the Pb(Zr,Ti)08 solid-solution series with more than 8 mole yo PbZfi, result in the formation of a two-phase material.The major phase would be a Pb(Zr, Ti)Oa solid solution having a lower zirConate/titanate ratio than that given by the bulk composition, and the minor phase would be 21-02 with, perhaps, some TiOI in solid solution (see Fig. 1 It is assumed that only a negligible deviation from stoichiometry can occur in Pb(Zr,Ti)G before the zirconia appears as a second phase. The electrical &ects of deaeasing the zirconate/titanate ratio of a tetragod or titanate-rich solid solution will be different from the effects accompanying a decrease of this ratio for the rhombohedral or zirconate-rich solid solution, because maximums in the values of the radii electromechanical coupling factor k,, and of the dielectric constant KS, occur near the tetragod-rhombohedral phase boundary.'*6Ceramic disks were sintered from lead zirconate-titanate powders that had been prepared by a coprecipitation technique described in detail elsewhere.' The powders were initially slightly deficient in lead oxide. The sintering was performed in a series of cycles in which the amount of lead oxide supplied to the furnace atmosphere from lead zirconate disks was varied from cycle to cycle. -A series of disks showing variations in weight change during shtering was produced. The weight changes during sintering were assumed to indicate the relative lead oxide contents of the disks. although it was realized that, in general, the disks -would not be homogeneous with respectto leadoxide distribution. The electrical properties of the disks were evaluated, in accordancewith IRE standards,' 24 h r after poling at 100°C for 5 min under a field of 36 kv/cm.The results for two series of disks are shown in Fig. 1. In the disks with the molar ratio of 0.497 (Fig. 1 (A)), the structure of the Pb(Zr,Ti)G solid solution was tetragonal. For this series, both the coupling factor and the dielectric constant decreased with decreasing PbO content. This effect is intexpreted as the result of adecreasem the Zirconate content of the solid solution, i.e. the composition of the solid solution moved away from the tetragonal-rhombohedra1 boundary. In the disks with the molar ratio of 0.539 (Fig. 1 ( B ) ) , the structure of the Pb(Zr,Ti)Ot solid solution was rhombohedral. For this second series, both the coupling factor and the dielectric constant...

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The kinetics of the thermal decomposition of purified pyrite to pyrrhotitc and sulfur in a dynamic argon atmosphere have been studied over the temperature range 600 to 653 "C. T h e reaction was follo~ved by the rate of weight loss as indicated by a quartz spring balance and also by the rate of progression of the pyrite/pyrrhotite interface into a cylindrical, compressed, polycrystalline pellet. The temperature coefficient of the reaction was foiind to be 69.5 f 5.9, 64.7 f 3.3, and 66.9 f 5.1 kcal mole-I, when the results were processed in three different \\lays.The pyrite/pyrrhotite interface was found to progress a t a linear rate into the pellet a t a given temperature; eq~~atiorrs were derived to express the variation of reaction rate with temperature.--lttempts to follow the early nucleation stage ol the decomposition, using massive mineral crystals, proved unsuccessful.The thermal deconlpositioil of the mineral pyrite (FeS2) to yield pyrrhotite (FeS1+,) and sulfur has been made the subject of many investigations (1-13) ; this work has recently been reviewed by Kullerud and Yoder (1). Most studies have been made by measuring sulfur vapor pressure values ( p s ) under equilibrium conditions over a range of temperatures. The enthalpy, A H , of the reaction, obtained froin these measurements, has given values ranging fro111 39 to 104 lccal ~nole-I for various investigators, most values lying in the 05 to 85 ltcal mole-' range. 31Iost \vorl;ers employed static conditions a t less than 1 a t m pressure; I.tical treatment as that employed by i\IcI

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