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It is shown by an analysis of the scale growth process that the scale of even approximately uniform composition formed in the reaction between gas and metal must consist of at least two layers. One layer is formed by the outward migration of metal ions and electrons through the scale; the other forms under the scale in the zone of consumption of the metal phase. Both layers form under completely different conditions. The inner layer is vital for the maintenance of metal transport to the bulk of the scale and grows at a gas pressure of the order of the dissociation pressure of the scale substance. It is demonstrated that the inner layer will develop cavities. A third layer may be formed in some secondary process, for example, that of recrystallization. It is therefore evident that the concept of a uniform process of scale growth is an oversimplification and fundamentally incorrect. This conclusion is supported by an investigation on copper iodide scale. The protective film formation on aluminum and the accelerated growth of oxide films on metals at the beginning‐of oxidation are explained on the basis of the considerations presented above.

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This paper describes the results of measurements of the heat capacity of nickel oxide, NiO, from 68-298.1°K., making use of the calorimeter described in a previous publication.1 From these results the entropy has been evaluated at 298.1°K., and from published heats of formation and heat capacities at higher temperatures the complete thermodynamic properties of the oxide have been derived.Material.-The nickel oxide used was a c. p. Baker analyzed grade containing less than 0.2% of impurities. Microscopic examination (X1000) showed the material to be made up of transparent cubic crystals of uniform size. This is the only form of the pure oxide which has been reported. The powder was dried for several days at 100°, and a sample then showed no ignition loss on heating to bright redness in a platinum crucible. The total charge of nickel oxide used in these measurements was 151.085 g. (in vacuo) or 2.0229 moles. Frequent checks of the calorimeter resistance against the calibrated thermocouple during the heat capacity measurements showed no significant changes in the calibration.

The action of the hypoglycemic compounds, tolbutamide, chlorpropamide, metahexamide, and phenethylbigu anide, on the biosynthesis of cholesterol has been investigated in vitro with both acetate-l-C14 and mevalonate-2-C14. The results show that the incorporation of acetate-l-C14 and mevalonate-2-C14 into cholesterol is inhibited by all compounds studied. The maximal inhibition occurs when the concentration of hypoglycemic compound is 4 X 10 ~3 m. It has been found that the inhibition of cholesterol biosynthesis by phenethylbigu anide takes place between isopentenyl pyrophosphate and the formation of squalene. The inhibition of cholesterol biosynthesis by the arylsulfonylurea compounds, on the other hand, takes place after the formation of squalene.

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