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The thermal decomposition of magnesium hydroxide is correlated with the effect of the temperature treatment on the strength of compacted discs of the material. The alteradon in the strength of the magnesium hydroxide which had been subjected to various temperatures between 450° and 800°C was obtained as well as by altering degassing conditions between ambient and 300°C. Up to twenty samples were broken at each of these conditions and the results show a skewed distribution of data points. The experiments on powders heat treated up to 800°C showed an increase in strength beyond 400°C. The TG data showed decomposition in the range 350°C to 500°C although farther weight loss was shown to be due to the presence of about 2–3% carbonate. The most useful correlation between the heat treatment and the strength is seen in the linear relationship between the surface area and the modules of rupture.

During carbonization, graphitizable aromatic organic compounds such as naphthalene, anthracene, phenanthrene and chrysene pass through a liquid or plastic-state mesophase of optical anisotropy, the lifetime of which is limited by its hardening to a semi-coke. Reflected polarized-light micrography, using cross polarizers with a gypsum plate, has been employed to characterize the carbonaceous mesophases of the different samples.

A versatile partial-pressure mass spectrometer system is described for measuring gaseous species thermally desorbed from solid surfaces. The system evaluates not only the ratio of masses present in the gaseous phase but also the specific mass (mg/g of solid) desorbed or decomposed during thermal treatment. The extension of the method to oxidation studies is also described. A study has been made of the evolution of gases from graphitic and nongraphitic carbons. These range in properties from a non-graphitic carbon, a PVDC charcoal of molecular sieve type, through a ground graphite of specific surface 102 m 2 /g to a nuclear type graphite of 0.6 m 2 /g. The formation of surface oxide on a clean surface at pressures of the order 0.2 mm Hg is evaluated along with the subsequent thermal decomposition of the surface oxide. The data from this paper together with other published work on graphites is used to illustrate the application of the thermal-desorption results to oxidation studies on carbons and graphites.