Mercury fulminate, decomposition

Singh [24] noticed that when heated for a few minutes at a temperature nearing that of immediate decomposition mercury fulminate crystals undergo decomposi-... 

Gamer and Hailes [462] postulated a chain branching reaction in the decomposition of mercury fulminate, since the values of n( 10—20) were larger than could be considered consistent with power law equation [eqn. (2)] obedience. If the rate of nucleation is constant (0 = 1 for the generation of a new nuclei at a large number of sites, N0) and there is a constant rate of branching of existing nuclei (ftB), the nucleation law is... 

The decomposition kinetics of mercury fulminate [725] are significantly influenced by ageing, pre-irradiation and crushing these additional features of reaction facilitated interpretation of the observations and, in particular, the role of intergranular material in salt breakdown. Following a slow evolution of gas ( 0.1%) during the induction period, the accelerator process for the fresh salt obeyed the exponential law [eqn. (8)] when a < 0.35. The induction period for the aged salt was somewhat shorter and here the acceleratory process obeyed the cube law [eqn. (2), n = 3] and E = 113 kj mole-1. 

Mercury fulminate, readily formed by interaction of mercury(II) nitrate, nitric acid and ethanol, is endothermic (AH°f (s) +267.7 kJ/mol, 0.94 kJ/g) and was a very widely used detonator. It may be initiated when dry by flame, heat, impact, friction or intense radiation. Contact with sulfuric acid causes explosion [1], The effects of impurities on the preparation and decomposition of the salt have been described [2],... 

An unstable powerful oxidant, it explodes between 40 and 70°C, or on friction or impact, sensitivity being as great as that of mercury fulminate [1], Detonation occurs at 95°C, and under vacuum explosive decomposition occurs above 10°C [2], See Potassium permanganate Sulfuric acid... 

Thermal decomposition of pure explosives such as primary explosives lead azide, lead styphnate, mercury fulminate etc. [35], monomethylamine nitrate [36] and explosive mixtures RDX + HMX mixtures [37]. 

Mercury fulminate also dissolves in many solutions of various salts, but in some of them (e.g. potassium iodide, sodium thiosulphate) it undergoes rapid decomposition. 

As previously stated, mercury fulminate is hydrolysed by heating in water in boiling water hydrolysis is very rapid. Farmer [31] noticed that on heating with water under pressure, mercury fulminate undergoes decomposition to metallic mercury. Marked decomposition also takes place on heating or standing for long periods at room temperature in an aqueous solution of ammonia or potassium... 

Mercury fulminate is relatively resistant to the action of dilute acids, in particular to that of nitric acid, but concentrated acids cause decomposition. Thus, under the influence of nitric acid decomposition occurs with evolution of NO, CO, acetic acid and mercuric nitrate. Under the influence of concentrated hydrochloric acid free fulminic acid is evolved (with an odour resembling that of hydrogen cyanide) as well as the decomposition products hydroxylamine hydrochloride, formic acid, mercuric chloride (Carstanjen and Ehrenberg [32] Scholl [33]). Mercury fulminate explodes on direct contact with concentrated sulphuric acid. 

Mercury fulminate undergoes rapid decomposition by the action of ammonium sulphide to form mercuric sulphide. The fulminate dissolves in sodium thiosulphate, according to the reaction ... 

Chemical stability and behaviour at higb temperatures. Mercury fulminate undergoes marked thermal decomposition even at 50°C. Rathsburg [37] found that a sample of the technical product stored at 50-60°C for 6 months in a dry atmo-... 

Fig. 30. Comparison of the rate of decomposition of mercury fulminate and other primary explosives at 75°C, according to Wallbaum [38].

Aqueous solutions of organic acids such as formic, acetic, and oxalic, decompose mercury fulminate, forming the corresponding mercuric salts. On the other hand, the action of dilute inorganic acids involves decomposition with formation of C02. 

Farmer quotes the following figures for the time required for the production of 5 cm3 of gas by heating mercury fulminate (this corresponds to the decomposition of 11% of substance) ... 

Farmer s experiments were repeated and extended by Garner and Hailes [41]. They examined the behaviour of mercury fulminate at about 100°C and came to the conclusion that during the initial induction period, decomposition is accompanied by a slow evolution of gas at a constant velocity (linear decomposition). At the end of this phase the main decomposition period begins with an increased rate of gas evolution. The authors noticed that if the fulminate is finely ground, rapid evolution of gas begins at once, without any initial period. 

A number of later authors, e.g. Prout and Tompkins [42], Vaughan and Phillips [43] have confirmed that the thermal decomposition of mercury fulminate is a chain reaction. 

Fio. 31. Influence of various methods of treatment on the thermal decomposition of mercury fulminate, according to Bartlett, Tompkins and Young [45]. /4—pie-irradiated, B—crushed, C—aged. 

Curve A represents the decomposition of mercury fulminate irradiated with ultra-violet rays, curve B the decomposition of ground mercury fulminate, and curve C the decomposition of ordinary (freshly-prepared) mercury fulminate. 

When crystals of mercury fulminate are heated at lower temperatures the decomposition reaction is localized mainly around lattice defects such as growth marks on the surface of crystals or points where dislocations emerge at the surface (Fig. 32(c)). 

The action of light. Mercury fulminate is sensitive to sunlight. Farmer found that on exposure to the sun s rays for 5 weeks in summer a test sample of fulminate showed considerable decomposition with gas evolution. 

The ignition temperature, when heated at the rate of 20°C/min, is 205-208°C i.e. higher than that of fulminate, but decomposition becomes evident on heating at a temperature slightly exceeding 100°C. The substance is exploded by a drop three times less than that of mercury fulminate. 

Tetrazene is stable at temperatures up to 75°C. At 100°C it undergoes marked decomposition. The ignition temperature of tetrazene is lower than that of mercury fulminate. On a metal plate, heated to 160°C, it explodes after 5 sec (mercury fulminate behaves in the same way at 190°C). According to Wallbaum [29] tetrazene explodes at 140°C on being heated at the rate of 20°C/min. 

Mixtures containing mercury fulminate, potassium chlorate, and antimony sulphide tend to destroy the inside of firearm barrels, since on decomposition the mercury fulminate evolves free mercury which causes erosion of the barrel at the... 

The result a are compared to a standard expl, such as picric icid, gunpowder or mercury fulminate, and expressed as a ratio known as figure of insensitiveness. This ratio represents the relative energies of the impact required to produce explosions of equal degrees of completeness from initial decomposition to complete detonation. Picric Acid is taken as 100, and explosives giving higher numbers are less sensitive while those giving lower numbers are more sensitive than picric acid. Ref R.Robertson, JCS 119 1,15(1921)... 

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