silica

A white or colorless crystalline compound, SiO₂, occurring abundantly as quartz, sand, flint, agate, and many other minerals and used to manufacture a wide variety of materials, especially glass and concrete.

Same as siliqua, 6.

Silica fused by the oxyhydrogen blowpipe may be worked in the plastic state, very much as glass is, and retains its amorphous character on cooling. Extremely delicate threads of this material may be drawn, and are used to suspend minute, readily mobile mirrors or other such parts of physical apparatus; they are also valuable as electrical insulators, being less affected by atmospheric moisture than threads of glass. Tubes, flasks, and beakers of moderate size have also been made from fused silica, and are useful on account of the hardness of the material, the high temperature it will bear without melting, the rapid changes of temperature it will sustain without cracking, and its superior resistance to most chemical reagents. Its behavior as respects dilatation by heat is also important. Berthelot has, however, recently shown that it is permeable by gases, particularly at high temperatures.

Silicon dioxid (SiO₂), or silicic anhydrid, a white or colorless substance, nearly insoluble in water and in all acids except hydrofluoric acid.

Silicon dioxide, SiO�. It constitutes ordinary quartz (also opal and tridymite), and is artifically prepared as a very fine, white, tasteless, inodorous powder.

Silicon dioxide.

Any of the silica group of the silicate minerals.

a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth’s crust as quartz or cristobalite or tridymite or lechatelierite