powder

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Related to powdery: powdery mildew

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 explosiveexplosive,
substance that undergoes decomposition or combustion with great rapidity, evolving much heat and producing a large volume of gas. The reaction products fill a much greater volume than that occupied by the original material and exert an enormous pressure, which can be
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.

Powder

 

a finely ground solid, a dispersed free-flowing material.

Powder is formed by dispersion of solids and by separation of the solid dispersed phase from supersaturated solutions or vapors. The manufacture of highly dispersed powders usually involves such substances as softening solutions, dispersing agents, and stabilizers. These facilitate pulverizing and prevent the agglutination of fine particles. Particle size in powders may vary from 10-4 to 10-1 mm. Powders with particles of identical size are called monodisperse powders, and those with particles of varying size are known as polydisperse powders. Fine powders, especially hygroscopic types, are subject to lumping and caking. Highly dispersed dry powder carried off by a gas or air flow becomes dust. Powder moistened with a liquid forms a paste or dough, and when powder is rapidly agitated in a sufficiently large volume of liquid, a suspension is produced.

Many types of commercial products are manufactured and used in powder form. They include materials used in metallurgy and silicate technology; mineral binders, fillers, and pigments; ingredients for plastics, rubbers, paints, and explosives; fertilizers and pesticides; detergents; food products; and medications. Products in powder form are often granulated or compressed into tablets to ensure convenience in handling and to reduce loss and improve sanitation.

REFERENCE

Voiutskii, S. S. Kurs kolloidnoi khimii. Moscow, 1964. Page 374.

L. A. SHITS


Powder

 

a friable solid form of medicine used internally or externally. Various synthetic preparations, antibiotics, and substances of plant and animal origin are used in powder form. The following substances are not prescribed as a powder: hygroscopic substances, such as calcium chloride and sodium bromide; mixtures of substances that are fluidized upon exposure to the air, such as phenylsalicylate and bromo-camphor or antipyrine and quinine; substances that easily decompose, such as silver nitrate mixed with organic matter; or substances that form explosive mixtures. Powders may be simple (consisting of a single substance) or compound; they can be divided or not divided into individual doses.

powder

[′pau̇d·ər]
(materials)
A general term for explosives.
A loose grouping or aggregation of solid particles, usually smaller than 1000 micrometers.

powder

1. a solid substance in the form of tiny loose particles
2. any of various preparations in this form, such as gunpowder, face powder, or soap powder
3. fresh loose snow, esp when considered as skiing terrain
References in periodicals archive ?
Rogelette Urgel, spokesperson of the regional PDEA office, said she could not say if the white powdery substance was cocaine.
The powdery mildew occurs throughout the year under favorable conditions and it is more severe in late sown kharif crop.
Sulfur continues to be the major AI applied in vineyards, predominantly for powdery mildew control.
Moreover, the classification and regression tree (CRT) was utilized to develop the prediction model of wheat powdery mildew.
Carol: It sounds to me like powdery mildew, which can appear if a plant is very dry or has had uneven watering.
Open-pollinated 'Waltham' produces 4- to 5-pound fruits on rambling vines that are susceptible to powdery mildew.
In Brazil, there are many barley crop damage function equations (DFE) for simple pathosystems, such as powdery mildew (REIS et al.
But asters are not alone in being susceptible and we don't stop cultivating rosesand rhododendrons, apples and soft fruit, cucumbers, peas, marrows because they are also vulnerable to powdery mildew.
If leaves are showing a white powdery deposit spray with a systemic fungicide straight away.
Area growers and other experts say recent steady rains have left some pumpkin vines, as well as other species of the Cucurbit family, covered in powdery mildew.
5 to 3% melt, where the primary particle size is in the range of a few microns, for example is typically achieved using a powdery melt.