Силикaгель

Химические свойства

white crystals or powder

Физические свойства

Colorless amorphous (i.e., fused silica) or crystalline (i.e., quartz) material having a low thermal expansion coefficient and excellent optical transmittance in far UV. Silica is insoluble in strong mineral acids and alkalis except HF, concentrated H₃PO₄, NH₄ HF₂ , concentrated alkali metal hydroxides. Owing to its good corrosion resistance to liquid metals such as Si, Ge, Sn, Pb, Ga, In, Tl, Rb, Bi, and Cd, it is used as crucible container for melting these metals, while silica is readily attacked in an inert atmosphere by molten metals such as Li, Na, K Mg, and Al. Quartz crystals are piezoelectric and pyroelectric. Maximum service temperature 1090°C.

Использование

Silicon(IV) oxide, amorphous is used as carriers, processing aids, anti-caking and free-flow agents in animal feed. Defoamer applications such as paint, food, paper, textile and other industrial applications. Synthetic silicon dioxides are used as a rheology control agent in plastics. It is also used to manufacture adhesives, sealants and silicones.

Определение

ChEBI: A silicon oxide made up of linear triatomic molecules in which a silicon atom is covalently bonded to two oxygens.

Общее описание

contains sodium stabilizing counterion

Опасность

Not toxic if ingested, inhaled silica dust can cause silicosis; carcinogen.

Сельскохозяйственное использование

Silica is silicon dioxide, one of the most abundant materials on the earth's crust. Quartz is an example of silica. It is used as a filler in fertilizers, and also, in the manufacture of glass, ceramics, abrasives, rubber and cosmetics.

Профиль безопасности

The pure unaltered form is considered a nuisance dust. Some deposits contain small amounts of crystahne quartz and are therefore fibrogenic. When diatomaceous earth is calcined (with or without fluxing agents) some sdica is converted to cristobalite and is therefore fibrogenic. Tridymite has never been detected in calcined batomaceous earth. See also other silica entries

Возможный контакт

Diatomaceous earth is used as a filtering agent and as a filler in construction materials, pesticides, paints, and varnishes. The calcined version (which has been heat treated) is the most dangerous and contains crystallized silica, and should be handled as silica. See also other entries on silica

Перевозки

This material is not singled out by DOT in its Performance-Oriented Packaging Standards.

Методы очистки

Purification of silica for high technology applications uses isopiestic vapour distillation from concentrated volatile acids and is absorbed in high purity water. The impurities remain behind. Preliminary cleaning to remove surface contaminants uses dip etching in HF or a mixture of HCl, H2O2 and deionised water [Phelan & Powell Analyst 109 1299 1984].

Несовместимости

Silica, amorphous is a noncombustible solid. Generally unreactive chemically. Incompatible with fluorine, oxygen difluoride, chlorine trifluoride. Soluble in molten alkalis and reacts with most metallic oxides at high temperature.

Утилизация отходов

Sanitary landfill.