Explosives-Associated Compounds

The utility of explosives lay in the strongly energetic and exothermic reaction initiated upon detonation or ignition. Most modem explosives are reasonably stable and require percussive shock or other triggering devices for detonation. Fortunately, subsurface Explosives-Associated Compounds (XAC) contamination usually occurs as dilute, aqueous solutions and thus presents no explosion hazard. However, masses of pure crystalline explosive material have been encountered in soils associated with wastewater lagoons, leach pits, bum pits, and perhaps firing ranges. 

Violence of the reaction, sometimes explosive, with e.g., acetic acid, benzene, ether, is associated with both their carbon and hydrogen contents. If nitrogen is also present, explosive fluoroamino compounds may be involved. Fibrous mate-rials-cotton, paper, wood-invariably ignite. 

The use of dry media (solvent-free) conditions, in which the reactants are absorbed on inert solid supports, in MW-heated reactions, has received a considerable amount of attention recently and has been used in the synthesis of a wide range of compounds [11-16]. These reactions generally occur rapidly and the method avoids hazards, such as explosions, associated with reactions in solvents in sealed vessels in which high pressures may be generated. Also the removal of... 

The determination of explosives in soils has been mostly commonly associated with the detection of unexploded ordnance such as land mines (both anti-personnel and anti-tank). Chambers et al. [70] designed sampling subsystems for soil/vapor sampling. A probe was used to extract and concentrate vapors of explosives in the pore volume of soil in the vicinity of land mines with sub-part-per-biUion detection limits for TNT and related explosive munitions compounds [70]. As an... 

TABLE 1.5 Molecular Weights and Vapor Molar Densities for Some Common Explosives and Associated Compounds... 

Although toxic releases, in general, are not the principal cause of major accidents (relative to fire and explosion) associated with the chemical industry, they are a just cause of "considerable public apprehension" [1327a]. This concern has been compounded by an event which occurred in Bhopal, India in December 1984, in which over 2500 people were killed by a single toxic release of methyl isocyanate. 

The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

The quality of bonding is related direcdy to the size and distribution of solidified melt pockets along the interface, especially for dissimilar metal systems that form intermetaUic compounds. The pockets of solidified melt are brittle and contain localized defects which do not affect the composite properties. Explosion-bonding parameters for dissimilar metal systems normally are chosen to minimize the pockets of melt associated with the interface. 

The sodamide must be free from sodium hydroxide and may be conveniently weighed under the 250 cc. of purified mineral oil which is used to rinse out the mortar. Care must be exercised in the use of old sodamide as it sometimes contains an explosive compound that might cause trouble. The nature of this explosive compound is not definitely known however, it appears to be associated with the development of a lemon yellow color. Should any part of the sodamide develop this color it is recommended that the whole be destroyed at once. 

Hazard, i.e. the potential of the material to cause injury under certain conditions (flammability, explosion limits in air, ignition and autoignition temperatures, static electricity (explosions have occurred during drying due to static electricity), dust explosion, boiling point, fire protection (specification of extinguishers, compounds formed when firing), R S (nature of special risk and safety precautions). Table 5.2-5 lists hazards associated with typical chemical reactions. 

The National Fire Protection Association classifies liquids by their explosion and flame-propagation abilities.16,17 These ratings are then used to specify the type of electrical equipment required. These standards have been adopted by OSHA. Woinsky18 gives a procedure for obtaining the material classifications of individual compounds and mixtures. 

The material is impact-sensitive when dry and is supplied and stored damp with ethanol. It is used as a saturated solution and it is important to prevent total evaporation, or the slow growth of large crystals which may become dried and shock-sensitive. Lead drains must not be used, to avoid formation of the detonator, lead azide. Exposure to acid conditions may generate explosive hydrazoic acid [1], It has been stated that barium azide is relatively insensitive to impact but highly sensitive to friction [2], Strontium, and particularly calcium azides show much more marked explosive properties than barium azide. The explosive properties appear to be closely associated with the method of formation of the azide [3], Factors which affect the sensitivity of the azide include surface area, solvent used and ageing. Presence of barium metal, sodium or iron ions as impurities increases the sensitivity [4], Though not an endothermic compound (AH°f —22.17 kJ/mol, 0.1 kj/g), it may thermally decompose to barium nitride, rather than to the elements, when a considerable exotherm is produced (98.74 kJ/mol, 0.45 kJ/g of azide) [5]. 

The epoxy resin component is made by a 2-stage process involving reaction of l-chloro-2,3-epoxypropane (epichlorhydrin) with isocyanuric acid to give the l,3,5-tris(2-hydroxy-3-chloropropyl) derivative, which is then treated with sodium hydroxide to eliminate hydrogen chloride to form the title compound. One batch contained more than the normal amount of hydroly sable chlorine, and when excess epichlorhydrin was distilled off, the residual material decomposed with explosive violence. It was later established that the abnormal chlorine content was associated with reduced thermal stability, and criteria for hydrolysable chlorine, epoxy content and pH have been set to prevent distillation of off-spec, material. 

However, to focus attention on the potential hazards always associated with the use of flammable and especially highly flammable substances, some 560 gases and liquids with flash points below 25° C and/or autoignition temperature below 225°C have been included in the text, their names prefixed with a dagger. The numerical values of the fire hazard-related properties of flashpoint, autoignition temperature and explosive (flammability) limits in air where known are given in the tabular Appendix 2. Those elements or compounds which ignite on exposure to air are included in the text, but not in the Table. 

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