Potassium perchlorate, decomposition

Nickei powder gives rise to dangerous reactions, which has led to accidents with potassium perchlorate (ignition), with chlorine at 600°C (ignition) and with ammonium nitrate at about 200°C (detonation). It catalyses the explosive decomposition of hydrogen peroxide. 

Potassium pentafluoroaluminate monohydrate, 2 371 Potassium perbromate, 4 335 Potassium perchlorate, 18 277 Potassium permanganate, 9 635-636 crystallographic studies on, 15 601 as a detoxicant, 15 621 decomposition of, 15 597 as an ignitable waste, 15 615 industrial-scale production of, 15 606 manufacture of, 15 601-606 for purifying carbon dioxide streams, 4 815... 

This reaction is quite vigorous, and becomes violent at temperatures above 500°C [2]. The actual decomposition mechanism may be more complex than equation 3.1 suggests. Intermediate formation of potassium perchlorate has been reported at temperatures just above the melting point, with the perchlorate then decomposing to yield potassium chloride and oxygen [5]. 

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. 

Potassium perchlorate is a white, non-hygroscopic crystalline material with a melting point of 6101C, considerably higher than the 356°C melting point of KCIO 3 It undergoes decomposition at high temperature... 

The composition and constitution of perchloric acid.—The composition of perchloric acid was established by F. von Stadion,80 and verified by J. L. Gay Lussac by the decomposition of potassium chlorate. 10 03 grams of perchloric acid were dissolved in water, and treated with a small excess of potassium carbonate. The soln. was evaporated to dryness with a slight excess of acetic acid, and washed with absolute alcohol to remove the potassium acetate. The residual potassium perchlorate was dried and weighed. The potassium perchlorate was ignited to drive off the oxygen. The results were ... 

Potassium perchlorate in the pure state, like potassium chlorate, is not an explosive, indeed the decomposition of the former is endothermic ... 

Gordon and Campbell [86], for instance, examined the exothermic decomposition of potassium perchlorate mixtures with carbon within the temperature range 300-360°C, while Grodzinski [87] studied the thermal decomposition of mixtures of various combustibles with potassium perchlorate. 

Noteworthy among the few reports in the literature on this subject is the work of Andersen, Bills, Mishuck, Moe and Schultz [3] on the mechanism of combustion of a mixture of 75% NH4C104 and 25% polyester with styrene. The work of Gro-dzinski [18] who investigated the thermal decomposition of the mixtures of various combustible substances with potassium perchlorate in a ratio of 20/80 by weight, is also of great interest. The combustible ingredients include asphalt and polyester resin from unsaturated (maleic) or saturated acids. 

The exothermic decomposition of the mixtures of potassium perchlorate with charcoal at 300-360°C was studied by Gordon and Campbell [19]. 

A feature of Bradyt F was the introduction of potassium perchlorate which increased the safety of the explosive by virtue of the potassium chloride formed on explosive decomposition. This proved effective in the experimental gallery. However, after being in use for many years, explosives of this type were withdrawn because of their comparatively high power (lead block expansion ca. 280 cm3) which was considered much too high for coal working, when more stringent regulations were introduced. 

Potassium perchlorate is prepared from potassium chlorate, the oxygen required for the oxidation being derived from the decomposition of some of the chlorate. This takes place in accordance with either of two distinct equations. Such reactions are called auto-oxidations. 

The chlorates, like the nitrates, are all readily soluble in water lead and silver chlorites, like the corresponding nitrites, are sparingly soluble salts and lead perchlorate is the only salt which does not easily dissolve. As already mentioned, chloric acid is readily decomposed when its aqueous solution is warmed chlorous acid is still less stable but perchloric acid, which may be prepared by distilling together potassium perchlorate with concentrated sulphuric acid, is relatively stable, seeing that it can be distilled without decomposition. It is an oily liquid, with acid taste it is apt to explode when brought into contact... 

Another non-equilibrium effect arises when the product composition contains a condensible substance. Solid propellant formulations based upon potassium perchlorate form solid potassium chloride and the acetylenic monopropellants upon decomposition form large quantities of carbon particles, as do very fuel-rich mixture ratios of hydrocarbon propellant systems. More recently metal and metal compounds have been used as fuels and form product oxides which are very high boiling point compounds that condense to varying degrees in the rocket chamber and nozzle. For example, estimates indicate that the normal boiling points of Li20, BeO,... 

The second reaction is accelerated by catalyzers, such as manganese dioxide or ferric oxide, or in fact any material with a rough surface. Too high a temperature also causes reaction (2) principally to take place. On the other hand, if the temperature is maintained at the right point, the salt is free from dirt, and the inside of the crucible is perfectly clean and free from roughness, the decomposition proceeds mainly according to reaction (1). Potassium perchlorate is very sparingly soluble in cold water and may be separated from potassium chloride and any undecomposed potassium chlorate by crystallization. 

After the electrolysis has been finished, solid sodium perchlorate may be separated from the solution, but usually other salts of perchloric acid are the final products, which are more suitable for commercial use. Potassium perchlorate is prepared by double decomposition of sodium perchlorate solution with potassium ehloride. If ammonium chloride or sulphate is used for the conversion, ammonium perchlorate will be obtained. Similarly, a mutual reaction with barium chloride will result in barium perchlorate. 

The solution became strongly acid and contained free hydrochloric and sulphuric acids. Hydrogen was gradually evolved at the negative pole. After the decomposition was complete the solution contained potassium perchlorate, which was also observed in the case of potassium trichlormethyl-sulphate. 

Summary Potassium perchlorate is readily prepared by fusing potassium chlorate in the presence of potassium chloride. The potassium chloride is used to decrease decomposition of the perchlorate and provide a stabilized uniform mixture. After the initial reaction, the potassium perchlorate is easily collected by thoroughly mixing the cooled mixture in water to dissolve the potassium chloride and any unreacted chlorate, followed by filtration to recover the insoluble perchlorate. 

The apparatus constant shall be determined as follows. First prepare the melting curves for pure tin, indium, potassium nitrate, and potassium perchlorate. Next using the value of heat of fusion found in the literature, determine the relationship between the temperature and the apparatus constant Calculate the apparatus constant at the extrapolated decomposition temperature, and, in the abovementioned equation, use the value so obtained. 

DSC(l) data were obtained with a Model DSC20 apparatus (Shimadzu Co., Ltd.) at Yoshida laboratory, The University of Tokyo. A sealed cell made of soft stainless steel was used as the sample cell K 1. The extrapolated decomposition temperature 1" was taken as the decomposition start temperature (Tdsc or Tdta). In DSC(l),the peak area was obtained by weighing the peak-area cutout. The apparatus constant, k, which is used to determine the DSC decomposition heat (Qdsc(1)) from the peak area, was determined by obtaining the values of heat of fusion for potassium nitrate, indium, tin, and potassium perchlorate. 

A sufficient rise in temperature initiates the decomposition of the potassium perchlorate, chiefly in accordance with the equation... 

Anhydrous perchloric acid is a powerful oxidizing agent that reacts explosively with many organic and inorganic materials. On decomposition, various gaseous products are formed. However, aqueous solutions of perchloric acid are not oxidizing at room temperature. This is explained on the basis of kinetic activation barriers. Most metals form perchlorate salts, and even molecular compounds, such as NO and NO2, also react with it to form ionic compoimds such as [NO]+ [0104]. Ammonium perchlorate is used as a solid-fuel propellant, particularly in missiles. Potassium perchlorate is also used in pyrotechnic formulations such as fireworks and flares. 

SAFETY PROFILE Moderately toxic by intravenous route. Questionable carcinogen with experimental tumorigenic and teratogenic data. Mixtures with oxidants (e.g., potassium chlorate, potassium nitrate, or potassium perchlorate) may be explosion hazards. When heated to decomposition it emits acrid smoke and irritating fumes. 

At this temperature very little decomposition with evolution of oxygen occurs in the absence of a catalyst. Potassium perchlorate may also be made by long continued electrolysis of a solution of potassium chloride, potassium hypochlorite, or potassium chlorate. 

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