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A 57Fe Moessbauer study of the Fe2O3–WO3 and Fe2O3–Cr2O3–WO3 systems has been carried out. Single phase materials could be prepared having the composition Fe2−xWO6−3x/2 (x = 0.28), the stoichiometric Fe2WO6 always contained detectable amounts of α-Fe2O3. The iron tungstates are found to be unstable to prolonged heating at 1000 °C. The Cr2−yFeyWO6 (0 < y ≤ 2) system was shown to be of the trirutile type when y ≤ 1.7 but multiphasic when y ≥ 1.7, these latter phases have structures based upon the iron and chromium tungstate phases, respectively. The Moessbauer parameters for the Cr2−xFeyWO6 compositions do not appear to behave in the same fashion as the related Fe2−xCrxTeO6 system.

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Rodent paw oedema is the basis of a multitude of acute and subacute test procedures for the evaluation of anti-inflammatory agents. Several methods for the determination of paw volume have been described, many being based on the method of' van Arman cited by Winter, Risley & Nuss (1962). These rely on the vertical displacement by the paw, of a pool of mercury. This, in turn, is estimated by pressure change or the alteration in electrical resistance of a graphite rod inserted in the mercury. These methods were found to be unsatisfactory in our hands. The main problem was lack of sensitivity. This could only be overconie by reducing the diameter of the mercury vessel thus malting more difficult the actual measurement of paw volume. This problem was particularly acute in the case of rats suffering from adjuvant disease with its consequent joint immobilization where accurate alignment of the limb proved difficult. A second problem was one of reproducibility. This was due to difficulties with the high degree of amplification required whcn a pressure system was used, or tocoating of thegraphite rod when a resistance method was used. Rather than embark on a program of development of one of these systems, we developed a method based on Archimedes principle.A bath of mercury (a 50 ml beaker contaifiing approximately 35 ml) was mounted on a one decimal top loading tare balance (Mettler P1210). In operation, the increase in weight registered on the balance was noted after insertion of the animal's paw into the mercury. It was possible to tare rapidly between readings when necessary and the relatively large surface area of mercury provided ease of access and accurate alignment of the paw. Volume of calibration rod !mt)A regression line showing the weight of mercury displaced bythe insertionof aknown volume is shown in Fig, 1. The volume/weight displaced relation was shown to be precise (correlation coefficient 0.998) and linear. 99 % confidence intervals for apparent volumes of 0.5 ml and 2.0 ml were 0-06 ml and 0.08 ml respectively.