smokeless powder: see explosive.

powder, any mass of fine particles or dust prepared by various mechanical means, e.g., grinding of solid substances, or by chemical means, e.g., precipitation from solutions. In a special sense, the word is applied to powdered propellant explosives, e.g., gunpowder, and to powdered substances that produce a bright light when ignited. See explosive.

bleaching powder, white or nearly white powder that is usually a mixture of calcium chloride hypochlorite, CaCl(OCl); calcium hypochlorite, Ca(OCl)₂; and calcium chloride, CaCl₂. Sometimes called chloride of lime, it can be prepared by reacting calcium hydroxide or slaked lime, Ca(OH)₂, with chlorine gas, Cl₂. It is used as a strong bleaching agent, as a disinfectant, and in making Javelle water. Bleaching powder was first produced in 1799 by Charles Tennant in Glasgow, Scotland.

Any of various surfactants (substances that reduce surface tension) used to dislodge dirt from soiled surfaces and retain it in suspension, allowing it to be rinsed away. The term usually refers to synthetic substances and excludes soaps. The characteristic features of a molecule of any detergent are a hydrophilic (water-attracting) end and a hydrophobic (oil-attracting) end. In ionic detergents, the hydrophilic property is conferred by the ionized part of the molecule. In nonionic detergents, hydrophilicity is based on the presence of multiple hydroxyl groups or other hydrophilic groups. Besides those used in water to clean dishes and laundry, detergents that function in other solvents are used in lubricating oils, gasolines, and dry-cleaning solvents to prevent or remove unwanted deposits. They are also used as emulsifying agents (see emulsion).

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Fabrication of metal objects from a powder rather than casting from molten metal or forging at softening temperatures. In some cases the powder method is more economical, as in making metal parts such as gears for small machines, in which casting would involve considerable scrap loss. In other cases, melting is impractical (e.g., because the melting point of the metal is too high). Powder metallurgy is also used to produce a porous product that will allow a liquid or gas to pass through it. Seealso metallurgy, sintering.

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