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The authors have investigated the chromatographic behaviour of esters having the general formulaA1, A2, B1, B2, B3being alkyl substituents. By means of the differences in equivalent chain lengths on two stationary phases, one polar, the other non-polar, it is possible to determine the “apparent polarity” of the ester function. The results show that this polarity is related to the steric hindrance of the function.

The resistivity-temperature curve of chromium dioxide, crystallizing in the rutile structure, is rather flat with a smooth maximum in the vicinity of the Curie point and, for higher temperature, an exponential decrease corresponding to a gap of 0.1 to 0.3 eV depending on samples and authors. The similarity of the Seebeck coefficient-temperature curves in chromium oxide and manganese telluride is pointed out. The oxide powder was prepared by thermal decomposition of the chromic anhydride, and had a CrO2 content higher than 95%. An infrared transmission spectrum was obtained by mixing 2% of oxide to 98% of potassium bromide and by pressing pellets under vacuum. The reliability of this technique is discussed.