| silicon | <chemistry, element> A nonmetalic element analogous to carbon. It always occurs combined in nature, and is artificially obtained in the free state, usually as a dark brown amorphous powder, or as a dark crystalline substance with a meetallic luster. Its oxide is silica, or common quartz, and in this form, or as silicates, it is, next to oxygen, the most abundant element of the earth's crust. Silicon is characteristically the element of the mineral kingdom, as carbon is of the organic world. Abbreviation: Si Atomic weight: 28. Synonym: silicium. See: Silica. Source: Websters Dictionary (01 Mar 1998) |
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| silicon compounds | Inorganic compounds that contain silicon as an integral part of the molecule. (12 Dec 1998) |
| silicon dioxide | <chemical> Silica. Transparent, tasteless crystals found in nature as agate, amethyst, chalcedony, cristobalite, flint, sand, quartz, and tridymite. The compound is insoluble in water or acids except hydrofluoric acid. Chemical name: Silica (12 Dec 1998) |
| silicone | Any of many polymers made up of alternating oxygen and silicon atomscombined with other organic groups. Silicone can be an oil, grease, gelor plastic, but all forms are resistant to heat, water and will notconduct electricity. It is used for a huge number of uses in industry (lubricants, paints, adhesives, coolants, etc.) Silicone is used inmedicine to replace body parts, and its use in breast implants has comeunder fire because there is evidence that these appliances may leak, andfurther evidence that leaked silicone may cause autoimmune disorders. (09 Oct 1997) |
| silicone elastomers | Polymers of silicone having properties similar to those of vulcanised natural rubber, namely the ability to be stretched to at least twice their original length and to retract very rapidly to approximately their original length when released. (12 Dec 1998) |
| silicone implant | Implant composed of silicone; common form of breast implant for augmentation. (05 Mar 2000) |
| silicone oils | Organic siloxanes which are polymerised to the oily stage. The oils have low surface tension and density less than 1. They are used in industrial applications and in the treatment of retinal detachment, complicated by proliferative vitreoretinopathy. (12 Dec 1998) |
| silicones | Any organosiloxane polymer in which the structural unit is usually -r2si-o-, where r is a monovalent organic radical. Physical properties of silicones depend on the size and type of the radical (methyl, phenyl), the r:si ratio, and the molecular configuration of the polymer (linear, cyclic, degree of crosslinking). (12 Dec 1998) |
| siliconisation | Noncovalent coating of surface with a layer of silicone oil making it less adhesive or reactive. See: silanising. (18 Nov 1997) |
| colloidal silicon dioxide | A submicroscopic fumed silica prepared by the vapor-phase hydrolysis of a silicon compound; used as a tablet diluent and as a suspending and thickening agent. (05 Mar 2000) |
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