Meta-silicon acid

Keywords Silica Clusters / Meta-Silicon Acid / Quantum-Chemical Modeling / Semiempirical AMI and PM3 Approximations / Vibrational Spectroscopy... 

It was postulated that the silicon dioxide molecule is a first intermediate product in the route from silicon tetrachloride to fumed silica. Due to high temperatures in the flame the ortho-silicon acid or meta-silicon acid will not be the main product of silicon tetrachloride hydrolysis or/and oxidation. The silicon dioxide molecule is well known to be stable at high temperatures or in a matrix-isolated state. Therefore, we are able to use silicon dioxide molecules as initial silicon-containing substances to simulate silica particle formation. Meta-silicon acids are able to react with other meta-silicon acid molecules and produce bigger clusters. Three meta-silicon acid molecules form cyclic clusters with four-coordinated silicon atoms and two-coordinated oxygens (Fig. 1). At high temperatures this cluster may loose some water molecules from hydroxyl groups and... 

Silicic acid. Any oxyacid of silicon, such as orthosilicic acid, H4SK>4, meta-silicic acid, H2Si03. These substances are hypothetical compounds inferred from their metallic or organic derivatives. 

SILICIC. 1. Containing or pertaining to silicon. 2. Containing silicic acid (ortho) HrSiOa or silicic acid (meta) HiSiC or silicic acids of a higher degree of hydration (disilicic acids, trisilicic acids, etc.). 

Phosphoric acids form many auto- and hetero-complexes, in which respect they are similar to the acids of vanadium and its congeners, as well as those of silicon. Three degrees of hydration, known as ortho-, pyro- and meta-, are also found, with certain differences, with other members of Group V. 

CHEMICAL PROPERTIES stable from 870-914C (1598-1677 F) at atmospheric pressure persists as a meta-stable phase below 8°C (46.4°F) forms low tridymite below 1 °C (34°F) and middle tridymite from 117-1°C (242.6-34°F) dissolved by hydrofluoric acid, forming the gas silicon tetrafluoride slowly attacked by heating with concentrated phosphoric acid rarely attacked by alkalies FP (NA) LFL/UFL (NA) AT (NA) HC (NA) HF (-910.7 kJ/mol crystal at25°C) Hf(8.51 kJ/mol at 1883K). 

Note Photosensitizers are as follows Photofrin , polyhematoporphyrin ethers ALA, aminolevulinic acid mTHPc, meta-tetetrahydroxyphenylchlo-rin SnET2, tin etiopurpurin, Lutetium Texaphyrin, a pendadentate aromatic metalloporphyrin BPD-MA, benzoporphyrin derivative mono acid HPPH, 2-[l-hexyloxyethyl]-devinylpyropheophorbide-a PC4, a silicon phthalocyanine AMD, age-related macular degeneration. 

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