![]() Oxygen composition is even more constant at 45 ± 8%. The nitrogen content of a wide variety of nitrogen-containing explosives is 31 ± 12%. The correlation between nitrogen and oxygen content is roughly linear, as shown in the scatter plot in Figure 4.1. The majority of high-explosive formulations use inorganic or organic nitrate or nitro functional groups as the oxidant. These general observations suggest that a focus on the percentage composition of the most electronegative elements might be a useful identifier of explosive formulations. įIGURE 4.1 Plot of the weight percent of oxygen versus nitrogen for the high explosives based on nitrogen listed in Table 4.1. Hexanitrohexaazaisowurtzitane (HNIW or CL20)ĪFor additional listings of explosives considered important in forensic investigations, see TWGFEX: The Technical Working Group for Fire and Explosions. TABLE 4.1 Some Representative Common High Explosives and Their Compositions a Black powder, which is a less energetic material, uses both charcoal and elemental sulfur as reductants. Occasionally, metal powders of the lighter elements (aluminum or magnesium) are added as supplemental reducing agents in explosive mixtures. The light elements carbon and hydrogen usually serve as the reducing components of HE formulations. The preponderance of highly electronegative elements in explosives is one reason why their detection by IMS (ion mobility spectrometry), which employs electron attachment to neutral explosive molecules, succeeds. Also, fluorine’s extreme oxidizing power may lead to unstable explosive formulations. Chlorine and fluorine are used less often in explosives because of its difficult chemistry and greater expense. Therefore, one common aspect of HE compositions is a large percentage of the more electronegative elements nitrogen and oxygen. Strong oxidizing agents require the use of the most electronegative elements nitrogen, oxygen, fluorine, and chlorine. For example, the carbonyl stretching absorption in the infrared spectrum at 1740 cm -1 is intense and diagnostic of acetone.Īll explosives must contain both oxidizing and reducing agents. However, the high volatilities of these compounds might make it feasible to detect the vapor plume by molecular spectroscopic techniques, such as microwave or infrared (IR) spectroscopy. These explosives have the same elemental composition as several organic compounds, including the specialty polymer poly(propylene adiponate). The diacetone and triacetone peroxides (e.g., TATP) pose the greatest problem for a detection scheme based solely on elemental constituents. ![]() The latter compound is carcinogenic and was a former dye intermediate that is being phased out. One was TNT, which has the same composition as dinitroanthranilic acid. Only two explosive elemental compositions had other isomers among the 90,000 chemicals in the catalog. The empirical formulas of all of the high explosives in Table 4.1 were entered in the online Aldrich catalog of common laboratory and industrial chemicals and polymers. If elemental formulations are considered, few common chemicals would be mistaken for explosives. It also contains some other explosive types for comparison. Table 4.1 provides a summary of high explosives that would be relatively simple to prepare or that could reasonably be obtained by a determined individual. The diversity of molecular features found in explosives suggests that a consideration of the elemental compositions might lead to new or improved detection approaches. May be added to solids such as ammonium nitrate, which have excess oxidizing power, in order to increase the explosive yield. Reductants (e.g., aluminum powder, fuel oil) For example, Semtex is a blend of cyclomethylenetrinitramine (RDX) and PETN. ![]() Mixtures of high explosives are frequently used. High explosives consist of an intimate mixture of oxidant and reductant, either within a single molecule, such as nitroglycerin, pentaerythritol tetranitrate (PETN), trinitrotoline (TNT), or triacetone triperoxide (TATP), or within an ionic solid, such as ammonium nitrate, when mixed with fuel oil. The devastating shock wave that accompanies detonation of a high explosive (HE), results in widespread damage and loss of life. Several such explosives, as well as some plasticizers and taggants found in plastique explosives, are listed in Table 4.1 along with their abbreviations. 1, 2 The problem of terrorism and suicide bombers, however, narrows the focus to high explosives. While few chemicals find use as military explosives ( Table 4.1), these can be combined with platiscizers and other materials to create a plethora of formulations.
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