The magnetic susceptibilities of single-crystal V2O3 have been measured by the Faraday method along and perpendicular to the trigonal axis between 300° and 700°K. Both χ‖ and χ⊥ have a high-temperature transition, as was expected, which occurs over a range of temperature from 450° to 550°K. An approximate fit of the data can be obtained with a Curie-Weiss law including a temperature-independent term with one set of parameters below 400°K and a different set above 550°K. It is found that the reciprocal susceptibility curve over the entire temperature range is at least cubic in T, indicating a rather complicated temperature dependence for the density of states function in the band approximation.

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This is a word of caution to anyone using ionization chambers protected by thin rubber sheaths in water. Four Farmer-type ionization chambers contaminated with talcum powder were received for calibration by the Accredited Dosimetry Calibration Laboratory at the University of Texas M. D. Anderson Cancer Center. The chambers show a marked energy dependence (5% to 20%) to soft orthovoltage x rays. The response of the contaminated chambers is compared with the chambers' response before contamination and after cleaning. Techniques for identifying contaminated chambers and suggestions for cleaning them are presented.

Magnetic-susceptibility measuxements have been used to locate the low-lying crystal-field levels of SrClo. Yb '. The two upper levels arising from the crystal-fieM-split E5g2 manifold were located by optical-absoxption spectra. The five crystal-field levels were found to lie at 0, 155, 650, 10193, and 10612 cm . A theoretical analysis showed that the magnetic-susceptibility, optical-absorption, and electron-spin-resonance data couM not be corxelated without the use of second-order cxystal-field mixing. In spite of the reasonably good correlation among the three experiments, the analysis, which was based on an electxostatic model, did give some unexpected le8ults fol" some of the mole 1mpox'tant physical quantltlea, This may indicate the importance of covalency and overlap in this cxystal system similar to that already found for Caw, :Tm".