Ignition powder

Sodium fluorosulfate may be prepared by the action of fluorosulfuric acid on powdered, ignited sodium chloride (13) or of sulfur trioxide on sodium fluoride (48). In general, the alkah metal fluorosulfates may be prepared from the ammonium salt by evaporating a solution containing that salt and an alkah metal hydroxide (77). The solubiUties of some Group 1 and 2 fluorosulfates in fluorosulfuric acid have been deterrnined (93). 

Zirconium is a highly active metal which, like aluminum, seems quite passive because of its stable, cohesive, protective oxide film which is always present in air or water. Massive zirconium does not bum in air, but oxidizes rapidly above 600°C in air. Clean zirconium plate ignites spontaneously in oxygen of ca 2 MPa (300 psi) the autoignition pressure drops as the metal thickness decreases. Zirconium powder ignites quite easily. Powder (<44 fim or—325 mesh) prepared in an inert atmosphere by the hydride—dehydride process ignites spontaneously upon contact with air unless its surface has been conditioned, ie, preoxidized by slow addition of air to the inert atmosphere. Heated zirconium is readily oxidized by carbon dioxide, sulfur dioxide, or water vapor. 

As discussed in 2-6.3 and 6-4.2, powder ignition via bulking brush discharge requires the coincidence of several factors, each of which has an associated probability. The minimum conditions are... 

The metal powder ignites in antimony trichloride vapour. 

Matignon, C., Compt. rend., 1900, 130, 1391 Aluminium powder ignites in carbon disulfide vapour. 

Aluminium powder ignites in chlorine without heating, and foil reacts vigorously with liquid bromine at 15°C, and incandesces on warming in the vapour [1], The metal and iodine react violently in the presence of water, either as liquid, vapour or that present in hydrated salts [2], Moistening a powdered mixture causes incandescence and will initiate a thermite mixture [3],... 

Powdered aluminium ignites in the vapour of arsenic trichloride or sulfur dichloride, and incandesces in phosphorus trichloride vapour [1], Above 80°C, aluminium reacts incandescently with diselenium dichloride [2], The powder ignites in contact with phosphorus pentachloride [3],... 

Mellor, 1941, Vol. 2, 292 1956, Vol. 2, Suppl. 1, 380 1943, Vol. 11, 26 Liquid chlorine at —34°C explodes with white phosphorus, and a solution in heptane at 0°C ignites red phosphorus. Boron, active carbon, silicon and phosphorus all ignite in contact with gaseous chlorine at ambient temperature. Arsenic incandesces on contact with liquid chlorine at —34°C, and the powder ignites when sprinkled into the gas at ambient temperature. Tellurium must be warmed slightly before incandescence occurs. 

The black powder ignites if ground or heated in air [1], The oxide obtained by oxidation of chromium amalgam is pyrophoric [2],... 

Mellor, 1941, Vol. 2, 490 1961, Vol. 2, Suppl. 2.1, 633 1946, Vol. 5, 217 Intimate mixtures of sodium peroxide with aluminium, magnesium or tin powders ignite on exposure to moist air and become incandescent on heating in air or on moistening with water. Exposure of such mixtures to carbon dioxide causes an explosion. (Interaction of the peroxide and carbon dioxide is highly exothermic.) Sodium is oxidised vigorously at 500°C. 

Uranium powder ignites in fluorine at ambient temperature, in chlorine at 150-180°, in bromine vapour at 210-240° and in iodine vapour at 260°C. 

The relative rarity of dust and powder ignitions makes them a unique sort of industrial safety threat. Because their occurrence is not routine, operating personnel eventually relax their guard, and too often this sort of behavior leads to dangerous incidents. The evidence that dust explosions are almost unknown within fluidized beds is an especially challenging problem for the safety officer, who must encourage vigilance even when no one remembers the last electrostatic incident. 

Anon., ABCM Quart. Safety Summ., 1933, 4, 15 A mixture of sawdust and bleaching powder ignites when moistened. 

Boron does not react with water at ambient temperatures. The powdered amorphous form, however, reacts slowly at 100°C producing horic acid. The amorphous metal reacts slowly with dilute mineral acids at ambient temperatures the crystalline form is inert. The former, however, reacts vigorously with concentrated nitric acid. The amorphous powder ignites in oxygen at... 

KayakuKySkaishi 23(4), 177-85 f 1962) CA 60, 1528(1964) [pA Translation 139 (Nov 1968) Priming characteristics of powdered ignition chges] 15) W. G. Finnegan et al, USP 3055 780(1962) 8c CA58, 407(1963) [Highly effective Initiation compn for bridge wires is formed from LMNR 98 8c poly(2-methyl-... 

The importance of good housekeeping must be emphasized. Any accumulation of Zr dust or powder on work benches, floors or clothes of personnel must be removed promptly. The pyrophoric properties of Zr dust or powder requires the selection of either wet or dry methods of dust collection A limited amount of moisture can make Zr powder ignition sensitive, but attempts to collect the dust dry by suction or convection flow risk dust expins which are easily initiated by static discharge or spontaneous combustion. Because nitrogen will also react with Zr,... 

Borides Carbon boride, CB6. and silicon borides SiB3 and SiB6 are hard, crystalline solids, produced in ihe electric furnace magnesium boride, Mgi B2, brown solid, by reaction of boron oxide and magnesium powder ignited, forms boron hydrides with HC1 calcium boride, Ca3 B2, forms boron hydrides and hydrogen gas with IIC1. 

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