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abrasive

(Encyclopedia)abrasive, material used to grind, smooth, cut, or polish another substance. Natural abrasives include sand, pumice, corundum, and ground quartz. Carborundum (silicon carbide) and alumina (aluminum oxi...

earth, in chemistry

(Encyclopedia)earth, in chemistry, metallic oxide not readily reducible by chemical means, e.g., alkaline earths, rare earths, and alumina. The name is also applied to certain absorbent clays, e.g., fuller's earth,...

grinding

(Encyclopedia)grinding, process by which surface material is removed from an object, usually metal, by the abrasive action of a rotating wheel or a moving belt that contains abrasive grains. A grinding wheel can be...

thorium

(Encyclopedia)thorium thôrˈēəm [key] [from Thor], radioactive chemical element; symbol Th; at. no. 90; mass number of most stable isotope 232; m.p. about 1,750℃; b.p. about 4,790℃; sp. gr. 11.7 at 20℃; va...

nitroglycerin

(Encyclopedia)nitroglycerin nīˌtrōglĭsˈərĭn [key], C3H5N3O9, colorless, oily, highly explosive liquid. It is the nitric acid triester of glycerol and is more correctly called glycerol trinitrate. It is insol...

corundum

(Encyclopedia)corundum kərŭnˈdəm [key], mineral, aluminum oxide, Al2O3. The clear varieties are used as gems and the opaque as abrasive materials. Corundum occurs in crystals of the hexagonal system and in mass...

citric acid

(Encyclopedia)citric acid or 2-hydroxy-1,2,3-propanetricarboxylic acid, HO2CCH2C(OH)(CO2H)CH2CO2H, an organic carboxylic acid containing three carboxyl groups; it is a solid at room temperature, melts at 153℃, an...

sodium silicate

(Encyclopedia)sodium silicate, any one of several compounds containing sodium oxide, Na2O, and silica, Si2O, or a mixture of sodium silicates. Sodium orthosilicate is Na4SiO4 (or 2Na2O·SiO2); sodium metasilicate i...

brownstone

(Encyclopedia)brownstone, red to brown variety of sandstone. Its unusual color is caused in some instances by the presence of red iron oxide which acts as a cement, binding the sand grains together. Vast thicknesse...

lithium

(Encyclopedia)lithium lĭthˈēəm [key] [Gr.,=stone], metallic chemical element; symbol Li; at. no. 3; interval in which at. wt. ranges 6.938–6.997; m.p. about 180.54℃; b.p. about 1,342℃; sp. gr. .534 at 20�...