Magnesia, properties

Table 19. Production Conditions and Resultant Magnesia Properties...

L. magnes, magnet, from magnetic properties of pyrolusite It. manganese, corrupt form of magnesia)... 

Acid—Base Chemistry. Acetic acid dissociates in water, pK = 4.76 at 25°C. It is a mild acid which can be used for analysis of bases too weak to detect in water (26). It readily neutralizes the ordinary hydroxides of the alkaU metals and the alkaline earths to form the corresponding acetates. When the cmde material pyroligneous acid is neutralized with limestone or magnesia the commercial acetate of lime or acetate of magnesia is obtained (7). Acetic acid accepts protons only from the strongest acids such as nitric acid and sulfuric acid. Other acids exhibit very powerful, superacid properties in acetic acid solutions and are thus useful catalysts for esterifications of olefins and alcohols (27). Nitrations conducted in acetic acid solvent are effected because of the formation of the nitronium ion, NO Hexamethylenetetramine [100-97-0] may be nitrated in acetic acid solvent to yield the explosive cycl o trim ethyl en etrin itram in e [121 -82-4] also known as cyclonit or RDX. 

Properties. The physical properties of magnesium hydroxide are Hsted in Table 8. The crystalline form of magnesium hydroxide is uniaxial hexagonal platelets (Fig. 4). Magnesium hydroxide begins to decompose thermally above 350°C, and the last traces of water are driven off at higher temperatures to yield magnesia. 

In addition to the four compounds discussed above, the final Portland cement may contain gypsum, alkali sulfates, magnesia, free lime and other components. These do not significantly affect the properties of the set cement, but they can influence rates of hydration, resistance to chemical attack and slurry properties. 

Abdelrazig, B. E. I., Sharp, J. H. El-Jazairi, B. (1989). Microstructure and mechanical properties of mortars made from magnesia-phosphate cement. Cement Concrete Research, 19, 247-58. 

Montross CS, Yokokawa H, Dokiya M, and Bekessy L. Mechanical properties of magnesia-doped lanthanum chromite versus temperature. J. Am. Ceram. Soc. 1995 78 1869-1872. 

In his memoir Be magnesia nigra, 1774, C. W. Scheele 2 pointed out that the chlorine water he discovered possessed the property of bleaching vegetable colours. He said ... 

This discovery was soon followed by the isolation of barium, strontium, and calcium. By analogy, it was further inferred that all amorphous powders—alumina, magnesia, etc.—possessing similar properties, were metallic oxides. As a result, when a new earth is now discovered, chemists believe, by faith, that it is the oxide of a metal even in cases where the supposed metal has never been isolated. 

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