Figure Common placards and pictograms for explosive materials left to right : DOT placard for Division 1. Listed below are some specific, representative chemical reactive hazards in laboratories that can lead to fires or explosions. Keep in mind, this list is not exhaustive; space does not permit us to list all the potential reactive hazards that could exist in a laboratory.
Consult the resources mentioned in Section I of this Chapter for more information. This explosion within a storage cabinet resulted from nitric acid mixed with an organic solvent in a closed container.
The pressure build-up ruptured the container and blew the cabinet doors open. A bottle of dried-out picric acid, discovered in a UNC laboratory in , which has become a highly shock-sensitive Division 1. Back to Chapter Ten. Proceed to Chapter Twelve. Search Articles. Title Laboratory Safety Manual - Chapter Explosive and Reactive Chemical Hazards Purpose This chapter provides resources that can help you prevent a laboratory accident due to mishandling explosive substances, or mixing incompatible reactive substances.
Introduction The variety of chemicals commonly present in the laboratory poses the potential for accidental hazardous chemical reactions or explosions. Hazardous reactions may cause any one or more of the following: dispersal of toxic dusts, mists, particles explosion fire formation of flammable gases formation of shock or friction sensitive compounds formation of substances of greater toxicity formation of toxic vapors heat generation pressurization in closed vessels solubilization of toxic substances violent polymerization volatilization of toxic or flammable substances It is easy to become complacent with chemicals used everyday in routine procedures.
Explosive Materials in Laboratories Explosives are solid, liquid, or gaseous chemicals that can cause a sudden, almost instantaneous release of pressure, gas, and heat when subjected to shock, pressure, or high temperature. Common Reactive Hazards in Laboratories Listed below are some specific, representative chemical reactive hazards in laboratories that can lead to fires or explosions.
Acetylenic Compounds are explosive in mixtures of 2. Acetylene C 2 H 2 subjected to an electrical discharge or high temperature decomposes with explosive violence. Dry acetylides detonate on receiving the slightest shock. Alkyllithium compounds are highly reactive and pyrophoric. Examples include n-butylithium and methyl lithium. They may ignite spontaneously upon exposure to air.
Fires or explosion can occur upon contact with water or moist materials. It should be stored under an inert atmosphere free from all ignition sources. Aluminum Chloride AlCl 3 is a potentially dangerous material because if moisture is present, decomposition can produce hydrogen chloride HCl and build up considerable container pressure. When opening a bottle that has been stored for a long time, completely enclose it in a heavy towel. Ammonia NH 3 reacts with iodine to produce nitrogen tri-iodide which is explosive , and with hypochlorites to produce chlorine.
Do not mix ammonia-based cleaners with bleach. Mixtures of ammonia and organic halides sometimes react violently when heated under pressure.
Aqua Regia is a mixture of nitric acid and hydrochloric acid, and is sometimes used for dissolving noble metals or as glassware cleaner. Try to avoid using aqua regia.
If you require it, make and use only what you need in a laboratory hood, and destroy it within the hood after use. Do not store it in closed containers; attempts to store aqua regia will most likely rupture the storage container.
Upon generation, the nitric acid begins to reduce, with evolution of toxic nitrogen dioxide gas. Carbon Disulfide CS 2 is highly toxic and highly flammable; when mixed with air, its vapors can ignite by a steam bath or pipe, a hot plate, or a glowing light bulb.
Chlorine Cl 2 may react violently with hydrogen H 2 or with hydrocarbons when exposed to sunlight. Diazomethane CH 2 N 2 and related diazo compounds require extreme caution. They are very toxic, and the pure forms gases and liquids explode readily. Diazald a precursor to diazomethane is a high explosive. Solutions in ether are safer, and are rendered harmless by dropwise addition of acetic acid. Diethyl, Isopropyl, and other Ethers particularly the branched-chain type may explode during heating or refluxing due to the presence of peroxides.
Ferrous salts or sodium bisulfite can decompose these peroxides, and passage over basic active alumina will remove most of the peroxidic material. Mark containers with the date received, date opened, and date to be discarded, and discard them before they are out of date.
Diethylzinc [ C 2 H 5 2 Zn] is a violently pyrophoric air-reactive , water-reactive, and light-sensitive liquid, and is generally sold in mixture with toluene, hexane, or other organic solvents. At concentrations above 1. The diversity of molecular features found in explosives suggests that a consideration of the elemental compositions might lead to new or improved detection approaches.
Table 4. It also contains some other explosive types for comparison. If elemental formulations are considered, few common chemicals would be mistaken for explosives. The empirical formulas of all of the high explosives in Table 4. Only two explosive elemental compositions had other isomers among the 90, chemicals in the catalog. One was TNT, which has the same composition as dinitroanthranilic acid.
The latter compound is carcinogenic and was a former dye intermediate that is being phased out. The diacetone and triacetone peroxides e. These explosives have the same elemental composition as several organic compounds, including the specialty polymer poly propylene adiponate. 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.
For example, the carbonyl stretching absorption in the infrared spectrum at cm -1 is intense and diagnostic of acetone. All explosives must contain both oxidizing and reducing agents. Strong oxidizing agents require the use of the most electronegative elements nitrogen, oxygen, fluorine, and chlorine. Therefore, one common aspect of HE compositions is a large percentage of the more electronegative elements nitrogen and oxygen.
Chlorine and fluorine are used less often in explosives because of its difficult chemistry and greater expense. 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.
The light elements carbon and hydrogen usually serve as the reducing components of HE formulations. Occasionally, metal powders of the lighter elements aluminum or magnesium are added as supplemental reducing agents in explosive mixtures. Black powder, which is a less energetic material, uses both charcoal and elemental sulfur as reductants.
Black and Smokeless Powders. TABLE 4. These general observations suggest that a focus on the percentage composition of the most electronegative elements might be a useful identifier of explosive formulations.
The majority of high-explosive formulations use inorganic or organic nitrate or nitro functional groups as the oxidant. The correlation between nitrogen and oxygen content is roughly linear, as shown in the scatter plot in Figure 4. This suggests that dual analysis of nitrogen and oxygen content might provide a more reliable indication of high explosives than techniques based on nitrogen content alone. Ammonium nitrate AN in particular is readily available and when mixed with fuel oil is capable of producing widespread explosive dam-.
Therefore, the ability to exploit the nitrogen and oxygen content in AN may provide a useful means of detection of this material in explosive devices. From a chemical point of view, the other possible elements of high electronegativity that might be employed in explosives are chlorine and fluorine. For example, perchlorate and chlorate salts are used in certain energetic materials formulations. Ammonium perchlorate, which is mixed with a powdered aluminum-polymer binder, finds use as a solid rocket fuel.
Metal powder-potassium chlorate mixtures are used in fireworks. Chlorine-based explosives could be detected by an elemental analysis approach, since a high chlorine-oxygen-nitrogen content is indicative of such species.
As terrorists and other potential bombers become more sophisticated, both in their choice of explosive materials and in the way these materials are procured, transported, and concealed, detection methods must be changed concomitantly. For example, in the near term, a new class of energetic materials, ionic liquids e. This could be corrected with the addition of fluorine to the list of electronegative elements scanned. Recommendation: Improved detection systems will lead to development of new explosives.
Research is needed on the identifica -. Drake, G. Propellants , Explosives , Pyrotechnics , 28 , Chapman, R. Axenrod, T. Tetrahedron Letters , 42, Existing explosive detection approaches for luggage rely on estimating physical characteristics, such as the density and approximate elemental nitrogen content, by using X-ray scattering e.
Vapors that are emitted from a bomb may be present at concentrations two to four orders of magnitude less than the equilibrium vapor pressures shown in the figure, both because of enclosure in a bomb package and because explosive compositions containing other compounds may have lower vapor pressures than those shown for the pure explosive compounds.
In some cases, more volatile impurities e. Some energetic plasticizers 8 or taggants 9 used in plastique explosives, such as mononitrotoluene MNT , diglycol dinitrate DEGN , dimethyldinitrobutane DMNB , ethylene glycol dinitrate EGDN , or butanetriol trinitrate BTTN , are volatile enough for vapor detection of these species to be used as an indicator of the presence of explosive compounds.
Nitroglycerin, a high explosive and constituent of dynamite, is another volatile species that might be detected directly in the vapor phase. The vapor pressures of less volatile explosives are very temperature dependent. Explosives , Fifth Revised Edition. Dionne, B. Energetic Mater.
Courtesy of J. Parmeter et al. It is made by combining ammonia gas with liquid nitric acid, which itself is made from ammonia. Ammonium nitrate is classified as dangerous goods and all aspects of its use are tightly regulated. For decades, Australia has produced, stored and used ammonium nitrate without a major incident. This article was originally published on The Conversation. Read the original article.
Gabriel da Silva is a senior lecturer in chemical engineering at the University of Melbourne. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Stephanie R. The Chemistry of Explosions. The production of these very low energy stable bonds means that a great deal of energy is released.
It should be noted that most explosives contain these same elements. TNT itself is high energy and unstable. Because these groups are fairly large and in close proximity to each other they cause strain on the structure of the Toluene. Remember that groups of electrons repulse each other.
Other compounds under similar conformational strain are also explosive for this same reason. Primary High Explosives Among the high explosives, primary explosives are those that ultrasensitive to heat, shock, or friction and provide the major ingredients found in blasting caps or primers used to detonate other explosives. Secondary High Explosives Secondary high explosives are those chemicals that do not have to be contained to explode and are relatively stable and safe to handle.
Funkyyyyyy YouTube Collecting Evidence at the Scene of an Explosion The process for examining evidence at the site of an explosion is very similar to the process followed at the scene of a fire. Search systematically the entire scene and try to locate the epicenter origin of the explosion.
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