Fine powders

Dissolve 15-0 g. of A.R. barium nitrate and 130 g. of A.R. cupric nitrate trihydrate in 450 ml. of water at 80°. Prepare a solution of sodium chromate by dissolving 89 g. of recrystallised sodium dichromate dihydrate in 200 ml. of water and adding 112 5 ml. of cone, ammonia solution (sp. gr. 0-90). Add the warm solution (80°) of nitrates in a thin stream, with stirring, to the sodium chromate solution (at 25°). Collect the orange precipitate by suction Bltration, wash it with two 50 ml. portions of 5fiter, drain well, and dry at 75-80° for 12 hours powder finely. 

Fine powders Fines removal Fingernail polish Fining... 

Sample preparation consists in reducing the sample to a powder fine enough (usually 200 mesh or finer) so that further grinding causes no substantial change in counting rates. 

Dry dusts and powders Fine rubber dust, bakelite moulding powder dust, cotton dust, light shavings, soap dust, leather shavings 3000-4000 15-20... 

FERROALLOY POWDERS, FINELY DIVIDED METALS, THERMITE REACTIONS... 

ALKALI-METAL ALLOYS, ALKALI METALS DEVARDA S ALLOY, FERROALLOY POWDERS FINELY DIVIDED METALS, LANTHANIDE METALS LIGHT ALLOYS, METAL DUSTS METAL FIRES, MILD STEEL... 

Yellow, rhombic crystals or powder. Finely dispersered particles form explosive mixtures. Combustible. 

F.G. Powder. Fine grain Black Powder used in die 19th century in England as proplnt for smaller caliber cannons and as a bursting charge for shrapnel shells Ref Daniel (1902), p 300... 

Classification Fine Powder Fine Powder Fine Chips Coarse Chips... 

Zhang, Zhimei, Han, Hongxi and Sun, Miaoxin (2000). Preparation of nano copper powder. Fine Chemicals Industry, 17(2) 69-71 (in Chinese). 

Nevertheless, high loadings often cannot be achieved by pore-volume impregnation, since the required amount of the active precursor cannot be dissolved in the pore-volume of the support. Suspension of the support in a volume of the solution of the active precursor larger than the pore-volume and subsequent drying docs not lead to a uniform distribution of the active precursor over the internal surface of the support. The evaporation of the solvent proceeds essentially outside the pore system of the support and the active precursor is deposited where the solvent evaporates. With a powdered, finely divided support, however, that is continuously and intensively stirred, reasonable results can be obtained. Nonetheless the loading of the support is always inhomogeneous, and the procedure is very difficult to scale up satisfactorily. 

The resulting mixture of crude o-chlorophenylthiourea and ammonium chloride (58-62 g.) is powdered finely and suspended in 300 ml. of water. The mixture is warmed slowly to 70° with mechanical stirring, then allowed to cool to 35°, and the solid is filtered with suction. The yield of crude o-chlorophenylthiourea, melting at 140-144°, is 30-35 g. (54-63%). 

Technical sodium nitrite is never quite 100 per cent pure, and should be titrated before use. When diazotizations are being carried out frequently, it is convenient to have nitrite available in three forms (a) I N nitrite solution (1 mole of NaN02 in a liter) for preparation, see page 385 (b) 5 N nitrite solution (1 mole of NaN02 in 200 cc.) ana (c) solid nitrite.—The technical product is dried in a steam heated oven, then powdered fine and stored in an air-tight container (since it takes up moisture). The NaN02 content is determined by titration. 

Two most important properties of the wiek are the pore size and the permeability. The pore size (radius) determines the fluid pumping pressure (eapillary head) of the wiek. The permeability determines the frietional losses of the fluid as it flows through the wiek. Aetually there are several types of the wiek struetures available ineluding metal sintered powder fine fiber bundle, axially grooves, sereen mesh. 

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