Magnesium perchlorate, decomposition

The ground material (40-mesh) is dried in vacuo at room temperature over a desiccant (magnesium perchlorate) that permits practically no water vapor pressure. An assumption was made that at room temperature and in the absence of air, decomposition and oxidation would be negligible. It was found, however, that a direct application of this reference method was not practicable from a routine standpoint, because the time to reach equilibrium was exceedingly long (6 to 9 months). 

The use of the perchlorate as desiccant in a drybag where contamination with organic compounds is possible is considered dangerous [1], Magnesium perchlorate ( Anhydrone ) was inadvertently used instead of calcium sulfate (anhydrite) to dry an unstated reaction product before vacuum distillation. The error was realised and all solid was filtered off. Towards the end of the distillation, decomposition and an explosion occurred, possibly owing to the presence of dissolved magnesium perchlorate, or more probably to perchloric acid present as impurity in the salt [2]. 

Al Fakir, M. S., Progr. Astronaut. Aeronaut., 1981, 76, 5512—564 Admixture of lithium perchlorate [1] or zinc perchlorate [2] leads to decomposition with explosion at 290° or ignition at 240°C, respectively. The role of ammine derivatives of lithium and magnesium perchlorates in catalysing the thermal decomposition of ammonium perchlorate has been studied [3], and lithium perchlorate has a strong catalytic effect on the burning rate [4]. 

SAFETY PROFILE Moderately toxic by ingestion and skin contact. An experimental teratogen. A severe skin and eye irritant. Flammable liquid when exposed to heat, flame, or oxidizers. To fight fire, use water, foam, fog, CO2. Violent explosive reaction on contact with magnesium perchlorate or trimethyl platinum(IV) azide tetramer. When heated to decomposition it emits toxic fumes of POx. An intermediate in the production of pesticides, fire retardants, and organic phosphorus additives. See also ESTERS. 

There may be simultaneous or preliminary dehydration processes for hydrated salts. Group 1 metal perchlorates, as well as calcium, barium and silver perchlorates [59] are represented by reaction (2.13). Aluminium and iron(IIl) perchlorates are represented by reaction (2.14). The solid product of decomposition of magnesium perchlorate is a mixture of magnesium oxide and magnesium chloride. 

EXPLOSION and FIRE CONCERNS flammable gas NFPA rating Health 3, Flammability 4, Reactivity 3 volatile flammable liquid below room temperature polymerizes violently on contact with ammonia, alkali hydroxides, amines, metallic potassium, acids, aluminum chloride, iron (III) chloride, tin (IV) chloride, aluminum oxide, iron oxide, and rust reacts explosively with glycerol at 200°C vapor forms explosive mixtures with air vapors may travel to an Ignition source and flash back incompatible with bases, alcohols, air, copper, trimethyl amine, magnesium perchlorate, mercaptans, alkane thiols, bromoethane, and others explosive decomposition may occur in vapor or liquid phases use water spray, dry chemical, foam, or carbon dioxide for firefighting purposes. 

Devlin, D.J., Herley, P.J. (1986) Thermal-decomposition and dehydration of magnesium perchlorate hexahydrate. Thermochimica Acta, 104,159-178. 

The U.S. domestic capacity of ammonium perchlorate is roughly estimated at 31,250 t/yr. The actual production varies, based on the requirements for soHd propellants. The 1994 production ran at about 11,200 t/yr, 36% of name plate capacity. Environmental effects of the decomposition products, which result from using soHd rocket motors based on ammonium perchlorate-containing propellants, are expected to keep increasing pubHc pressure until consumption is reduced and alternatives are developed. The 1995 price of ammonium perchlorate is in the range of 1.05/kg. Approximately 450 t/yr of NH ClO -equivalent cell Hquor is sold to produce magnesium and lithium perchlorate for use in the production of batteries (113). Total U.S. domestic sales and exports for sodium perchlorate are about 900 t/yr. In 1995, a solution containing 64% NaClO was priced at ca 1.00/kg dry product was also available at 1.21/kg. 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Because of its higher melting point and less-exothermic decomposition, potassium perchlorate produces mixtures that are less sensitive to heat, friction, and impact than those made withKClO] [2]. Potassium perchlorate can be used to produce colored flames (such as red when combined with strontium nitrate), noise (with aluminum, in "flash and sound" mixtures), and light (in photoflash mixtures with magnesium). 

Therefore, the initial choice for an oxidizer is one with an exothermic heat of decomposition such as potassium chlorate (KCIO 3). However, mixtures of both chlorate and perchlorate salts with active metal fuels are too ignition-sensitive for commercial use, and the less-reactive - but safer - nitrate compormds are usually selected. Potassium perchlorate is used with aluminum and magnesium in some "photoflash" mixtures these are extremely reactive compositions, with velocities in the explosive range. 

DOT CLASSIFICATION 5.1 Label Oxidizer SAFETY PROFILE Moderately toxic by intraperitoneal route. Severe skin and eye irritant. A powerful oxidizer which has caused many explosions in industry. Potentially explosive reactions with alkenes (above 220°C), ammonia, arjl hydrazine + ether, dimethyl sulfoxide + heat, ethylene oxide, fluorobutane + water, organic materials, phosphorus, trimethyl phosphate. Reacts to form explosive products with ethanol (forms ethyl perchlorate), cellulose + dinitrogen tetraoxide + oxygen (forms cellulose nitrate). Avoid contact with mineral acids, butyl fluorides, hydrocarbons. A drying agent. When heated to decomposition it emits toxic fumes of MgO and Cr. See also MAGNESIUM COMPOUNDS and PERCHLORATES. 

COPPER CYANIDE (544-92-3) CCuN May be unstable and explosive. Contact with nitric acid causes decomposition, releasing toxic and flammable hydrogen cyanide fumes. Reacts violently with powdered magnesium (incandescence). Reacts, possibly violently, with strong oxidizers, chlorine, fluorine, peroxides metal chlorates, nitrates, nitrites, perchlorates. Can act as a polymerization catalyst keep away from easily polymerized materials. On small fires, use dry chemical powder (such as Purple-K-Powder), foam, or COj extinguishers. Thermal decomposition releases toxic and flammable hydrogen cyanide gas. 

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