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The lattice spacings of high-purity iron have been measured accurately between 20 and 1502°C. The results, together with previous low-temperature data, give data between the absolute zero and the melting-point (1534°C). The thermal expansion of the lattice and of bulk metal are in good agreement over the temperature range for which the latter has been studied accurately. At the A 2 point, there is no discontinuity in the lattice spacing. In contrast to the work of some previous investigators, we have found no observ­able difference between the coefficients of expansion of the lattice immediately above and below the A 2 point, and the results suggest that the forces responsible for ferromagnetism do not affect the interatomic distances by more than 1 part in 10000. At the A 3 point, the α → γ transformation is accompanied by an increase in the interatomic distance which, when expressed as a percentage change, is slightly less than the decrease in interatomic distance during the γ → δ change at the A 4 point. The change in bond length calculated by the Pauling equation for the change (f. c. c.⇌b. c. c.) lies between the observed values for the A 3 and A 4 points, and the accuracy of the equation is confirmed.

The dependence of the nonstoichiometry of (YBa,Cu,O,-,) (solid) has been studied over 5 orders of magnitude in oxygen pressure and from 573 to 1173 K. Hydrogen-reduction methods fpr determining the absolute oxygento-metal ratio were developed. The resulting data were used to derive a chemical thermodynamic representation of the experimental variables. The data were also compared with several other investigations to identify the selfconsistent sets of data. The present data and thermodynamic data from the literature were correlated on an Ellingham diagram. [

The extensive nonstoichiometry in the 〈U1–zGdzO2±x〉† phase was investigated experimentally and the data are represented by a chemical thermodynamic method. The experimental ranges of temperature, oxygen potential, and z were 1273 to 1773 K, 0 to −600 kJ/mol, and 0.1 to 0.8, respectively. For hypostoichiometry, ideal‐solution thermodynamics for the equilibrium 3Gd4/3O2+ 4UO2+ (O2) = 6U2/3Gd2/3O8/3 were used to represent the experimental data, while for hyperstoichiometry a nonideal solution was used for the equilibrium 4UO2+ (O2) = 2U2O5. The wide ranges in x and z led to an improvement of the previous analysis of literature data and led to partial molal Gibbs free energy values that are useful for any thermodynamic calculation involving the phase.

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