R. A. Heindl and N. H. Mohler of the U.S. National Bureau of Standards' refractories laboratory have recently completed an investigation of the relative oxidation rates of 20 domestic and foreign graphites, including both the flake and amorphous varieties. The study shows that the coarser sizes of graphites having a graphitic content of about 85% are difficult to oxidise either in air or in a stream of oxygen at 400°C. However, when fine and coarse sizes are combined, as in finished but unglazed crucible bodies, a slow oxidation begins at 400°C., and the rate increases at higher temperatures with a definite deterioration of the body. One result of the study has been the establishment of numerical constants for graphite oxidation rates in oxidising atmospheres.
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