Magnesium vapor studies

The reduction of porous silica with magnesium vapor is a highly exothermic reaction. The process with thermal moderators is an attractive route to generating highly mesoporous silicon (surface areas >500 m /g). Without thermal moderators, large batches of macroporous silicon can be generated by combustion synthesis. Electrochemical reduction with molten calcium or lithium salts rather than thermal reduction with magnesium is also under evaluation. The use of liquid aluminum to reduce mesoporous silica deserves much further study. 

Mg(THF), when the stoichiometry was 1 2. Monomeric and dimeric amidinate complexes of magnesium have been studied in detail with respect to potential applications of these compounds in the chemical vapor deposition of magnesium-doped Group 13 compound semiconductor films. The reactions and products are summarized in Scheme 16. ... 

Allan (A7) during his studies of ashed plant materials also investigated interferences. Using an air-acetylene flame, sodium, potassium, calcium, magnesium, and phosphate had no effect. In the air-coal gas flame, as employed by Elwell and Gidley (E2), recoveries of iron were only 80-90% when the test solutions contained an excess of calcium, copper, aluminum, titanium, and zirconium. With silicon added, iron recovery was 26%. Owing to incomplete vaporization of iron in the flame, sensitivities attained are higher in the air-acetylene flame and lower in the air-coal gas flame. Since iron is subject to oxidation in the flame, fuel-rich flames are preferable. 

An isolated diorganylmagnesium molecule in the gas phase usually adopts a linear structure with a central i p-hybridized magnesium atom and two negatively charged ligands at opposite positions. In practice, this situation is very difficult to achieve only a few organomagnesium compounds can be transferred into the gas phase as thermal decomposition normally precedes vaporization. In a gas-phase electron diffraction study of dineo-pentylmagnesium (Section II), a linear molecule was indeed found. 

Beryllium metal, previously etched with acid, reacts with phthalonitrile to yield beryllium phthalocyanine, the only square planar derivative of beryllium known (10). Both anhydrous beryllium and magnesium phthalocyanines react readily with moisture to form very stable dihydrates. Dehydration may be effected only by sublimation in vacuo. Sidorov has studied the interaction of sublimed layers of beryllium and magnesium phthalocyanines with water, by infrared spectroscopy (825). Some of the absorption bands arising from the phthalocyanine unit shift when water vapor is introduced. This behavior was not noted with other phthalocyanines (see Section VI,A). 

It is necessary to mention here the fact that water may also be in combination with, or associated with the negative ion, as well as with the positive ion. A salt such as hydrated magnesium sulfate will illustrate this. The composition of this substance is MgS04.7H20. It has been shown by vapor tension measurements that six of the water molecules bear the same relation to the molecule as a whole, but different from the seventh molecule. Furthermore, the study of the optical activity (rotation of the plane of polarized light) of the substance, indicates that one molecule of water is associated with the SO4 group. This indicates that the water may be present in combination with either of the two parts of the molecule which form the ions, or that both positive and negative ions may be hydrated. 

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