Ammonia metal dusting

The primary constituents to be measured are the pH of precipitation, sulfates, nitrates, ammonia, chloride ions, metal ions, phosphates, and specific conductivity. The pH measurements help to establish reliable longterm trends in patterns of acidic precipitation. The sulfate and nitrate information is related to anthropogenic sources where possible. The measurements of chloride ions, metal ions, and phosphates are related to sea spray and wind-blown dust sources. Specific conductivity is related to the level of dissolved salts in precipitation. 

Picric acid, in common with several other polynitrophenols, is an explosive material in its own right and is usually stored as a water-wet paste. Several dust explosions of dry material have been reported [1]. It forms salts with many metals, some of which (lead, mercury, copper or zinc) are rather sensitive to heat, friction or impact. The salts with ammonia and amines, and the molecular complexes with aromatic hydrocarbons, etc. are, in general, not so sensitive [2], Contact of picric acid with concrete floors may form the friction-sensitive calcium salt [3], Contact of molten picric acid with metallic zinc or lead forms the metal picrates which can detonate the acid. Picrates of lead, iron, zinc, nickel, copper, etc. should be considered dangerously sensitive. Dry picric acid has little effect on these metals at ambient temperature. Picric acid of sufficient purity is of the same order of stability as TNT, and is not considered unduly hazardous in regard to sensitivity [4], Details of handling and disposal procedures have been collected and summarised [5],... 

As a chemical group, toxicity of nitndes generally stems from the possible reactions with water to form toxic fumes (especially ammonia) rather than from the nitride. There are, of course, exceptions Fine powder or dust of the nitndes of the transition metals can be pyrophoric nitrides of the actinide metals are carcinogenic. 

This reaction is useful for determining the composition and constitution of azo dyes. The reducing agents employed are usually metal and acid, zinc dust and water or ammonia, stannous chloride, or sodium hydrosulphide in alkaline solution. The reaction is carried out with or without heat, until the suspended or dissolved colour gives place to a colourless product containing one or two primary amines. 

Reduction of nitrates in alkaline medium Ammonia is evolved (detected by its odour by its action upon red litmus paper and upon mercury(I) nitrate paper or by the tannic acid-silver nitrate test, Section III.38, reaction 7) when a solution of a nitrate is boiled with zinc dust or gently warmed-with aluminium powder and sodium hydroxide solution. Excellent results are obtained by the use of Devarda s alloy (45 per cent Al, 5 per cent Zn, and 50 per cent Cu). Ammonium ions must, of course, be removed by boiling the solution with sodium hydroxide solution (and, preferably, evaporating almost to dryness) before the addition of the metal. 

Zinc dust is stable against water or moisture, because the film of zinc hydroxide, Zn(0H)2, or basic zinc carbonate, 2ZnC03.3Zn(OH)2., formed on the particle surface protects the metal from corrosion. It is not easily soluble in sodium hydroxide solution in water, but it is soluble in a weak alkali solution such as sodium carbonate or bicarbonate generating hydrogen gas. It is also easily soluble in ammonia solution to form a complex salt, [Zn(NH3)4] (OH) 2- Zinc is attacked by chlorides, but not by ammonium perchlorate. The main use for zinc is in white smoke, which is created by zinc chloride particles. Zinc dust is quite reactive with hexachloroethane in presence of moisture or water, and it often causes fire when manufacturing smoke composition. It is thought that a trace of hydrochloric acid in the hexachloroethane causes the reaction. 

Filtering and Mixing. Since the reaction between ammonia and oxygen is catalytic in nature, it is very important that the effectiveness of the catalyst is maximized by keeping the catalyst surface area fully accessible by the gases. In particular, particles of metal or metal oxide may cause premature oxidation and affect the catalyst effectiveness. Therefore, air and ammonia passed to the mixer must be free from any suspended matter, dust, or mist (greater than 0.5 (pm) which could obscure or foul the catalyst surface [5]. 

The synthesis of furan-2-methanethiol was described by Reichstein and Staudinger (1928). Furfural (1.63) is converted into furfuryl disulfide (difurfuryl disulfide, 1.136) by treatment with the sulfide or hydrosulfide of an alkaline-earth metal or of ammonia. The disulfide in an alcoholic solution can be reduced, for example, by addition of zinc dust and a small quantity of acetic acid. A method has been described by Kofod (1955). 

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