Grain magnesia

The result of calcination is very reactive fine-grained magnesia. Because of its reactivity, it is called caustic magnesia. Calcination at temperature above 1700°C causes sintering of the calcined powder. The resulting magnesium oxide becomes dead burned with particles grown in size. 

As a purgative, the dose for adnlts is from a scruple to a drachm for infanta, from two to ten grains. As an antacid, the doso is from ten to thirty grains twice a day. It is conveniently given in milk. Magnesia has been used with success as on antidote to arsenic. —Pereira. 

The results with magnesia led us to a planned series of experiments with doped aluminas. Nickel was evaporated in vacuo onto the surface of grains of undoped or doped alumina or, alternatively, onto compact nickel. These preparations were then used as catalysts for the donor model reaction of formic acid dehydrogenation as above. Table II shows the results. 

Grain size and boundaries, impurities, additives, particle size, porosity, sintering temperature and time, heating and cooling rate, and shaping practice play an important role in controlling many physical, mechanical and chemical properties of magnesia-based bricks.29... 

Kig. 7. An orientation stability map for magnesia at 1400 °C. Each point corresponds to the orientation ofan observed grain. Faceted orientations are marked with an x and smooth orientations are marked with an empty square. An AFM image of a typical faceted surface is shown in the upper left hand part of the figure. The facets are approximately 500 A high. 

Hydrargyrum cum Creta [mercury with chalk] mdHydr. Cum Magnesia [mercury with magnesia] these are mild preparations, yet capable of producing salivation by their continued use. Dose, five to thirty grains or two to five grains for children. They are much employed in diseases of children attended with deficient biliary secretion. .. 

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