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An explosive is defined as a chemical that causes a sudden, almost instantaneous release of pressure, gas, and heat when subjected to sudden shock, pressure, or high temperature. Under the International Transport Association (IATA) hazard class system, explosives are listed as hazard class 1. Fortunately, most laboratories do not use many explosives; however, there are a number of chemicals that can become unstable and/or potentially explosive over time due to contamination with air, water, other materials such as metals, or when the chemical dries out.
If you ever come across any chemical that you suspect could be potentially explosive, do not attempt to move the container as some of these compounds are shock, heat, and friction sensitive. In these instances, you should contact HSE at hse@kaust.edu.sa immediately.
Explosives can result in damage to surrounding materials (hoods, glassware, windows, people, etc.), generation of toxic gases, and fires. If you plan to conduct an experiment where the potential for an explosion exists, first ask yourself the question; “Is there another chemical that could be substituted in the experiment that does not have an explosion potential?” If you must use a chemical that is potentially explosive, or for those compounds that you know are explosive, (even low powered explosives) you must first obtain prior approval from the Principal Investigator to use such chemicals. After obtaining prior approval from your Principal Investigator, thoroughly read the SDSs and any other chemical resources related to the potentially explosive compound(s) to ensure potential incidents are minimized.
If you discover a potentially explosive compound that exhibits any of these signs of contamination, then please contact HSE at hse@kaust.edu.sa
Occasionally, it is necessary to handle materials that are known to be explosive or that may contain explosive impurities such as peroxides. Since explosive chemicals might be detonated by mechanical shock, elevated temperature, or chemical action with forces that release large volumes of gases, heat, and often toxic vapors, they must be treated with special care. The proper handling of highly energetic substances without injury demands attention to the smallest detail. The unusual nature of work involving such substances requires special safety measures and handling techniques that must be understood thoroughly and followed by all persons involved.
Organic peroxides are a special class of compounds whose unusually low stability makes them among the most hazardous substances commonly handled in laboratories, especially as initiators for free-radical reactions. Although they are low-power explosives, they are hazardous because of their extreme sensitivity to shock, sparks, and other forms of accidental detonation. Many peroxides that are handled routinely in laboratories are far more sensitive to shock than most primary explosives (e.g., TNT), although many have been stabilized by the addition of compounds that inhibit initiation reactions. Nevertheless, even low rates of decomposition may automatically accelerate and cause a violent explosion, especially in bulk quantities of peroxides (e.g., benzoyl peroxide). These compounds are sensitive to heat, friction, impact, and light, as well as to strong oxidizing and reducing agents. All organic peroxides are highly flammable, and fires involving bulk quantities of peroxides should be approached with extreme caution.
Hydrogenation reactions are often carried out under pressure with a reactive catalyst and so require special attention. Along with observation of the precautions for the handling of gas cylinders and flammable gases, additional attention must be given to carrying out hydrogenation reactions at pressures above 1 atm.
The following list is not intended to be all-inclusive. Further guidance on reactive and explosive materials should be sought from other sources of information.
Can be explosive in mixtures of 2.5 to 80% with air. At pressures of 2 or more atmospheres, acetylene (C2H2) subjected to an electrical discharge or high temperature decomposes with explosive violence. Dry acetylides detonate on receiving the slightest shock. Acetylene must be handled in acetone solution and never stored alone in a cylinder.
(AlCl3) should be considered a potentially dangerous material. If moisture is present, there may be sufficient decomposition to form hydrogen chloride (HCl) and build up considerable pressure. If a bottle is to be opened after long storage, it should first be completely enclosed in a heavy towel.
(NH3) reacts with iodine to give nitrogen tri-iodide, which detonates on touch. Ammonia reacts with hypochlorites to give chlorine. Mixtures of NH3and organic halides sometimes react violently when heated under pressure. Ammonia is combustible and can form explosive compounds with silver as well. Inhalation of concentrated fumes can be fatal.
Both organic and inorganic, and some azo compounds can be heat- and shock-sensitive. Azides such as sodium azide can displace halide from chlorinated hydrocarbons such as dichloromethane to form highly explosive organic polyazides; this substitution reaction is facilitated in solvents such as dimethyl sulfoxide (DMSO).
(CS2) is both very toxic and very flammable; mixed with air, its vapors can be ignited by a steam bath or pipe, a hot plate, or a light b
(Cl2) is toxic and may react violently with hydrogen (H2) or with hydrocarbons when exposed to UV light.
(CrO3 C5H5N) may explode if the CrO3 concentration is too high. The complex should be prepared by addition of CrO3 to excess C5H5N.
(CH2N2) and related diazo compounds should be treated with extreme caution. They are very toxic, and the pure gases and liquids explode readily even from contact with sharp edges of glass. Solutions in ether are safer from this standpoint. An ether solution of diazomethane is rendered harmless by drop wise addition of acetic acid.
Including tetrahydrofuran and 1,4-dioxane and particularly the branched- chain type of ethers, sometimes explode during heating or refluxing because the presence of peroxides has developed from air oxidation. Ferrous salts or sodium bisulfite can be used to decompose these peroxides, and passage over basic active alumina can remove most of the peroxidic material. In general, however, old samples of ethers should be disposed of after testing, following procedures for disposal of peroxides.
(CH2N2) and related diazo compounds should be treated with extreme caution. They are very toxic, and the pure gases and liquids explode readily even from contact with sharp edges of glass. Solutions in ether are safer from this standpoint. An ether solution of diazomethane is rendered harmless by drop wise addition of acetic acid.
(DMSO), (CH3)2SO, decomposes violently on contact with a wide variety of active halogen compounds, such as acyl chlorides. Explosions from contact with active metal hydrides have been reported. Dimethyl sulfoxide does penetrate and carry dissolved substances through the skin membrane.
(C6H5CO2)2is easily ignited and sensitive to shock. It decomposes spontaneously at temperatures above 50 °C. It is reported to be desensitized by addition of 20% water.
Should not be kept in a container that is not designed to withstand pressure. Containers of other substances stored over dry ice for extended periods generally absorb carbon dioxide (CO2) unless they have been sealed with care. When such containers are removed from storage and allowed to come rapidly to room temperature, the CO2 may develop sufficient pressure to burst the container with explosive violence. On removal of such containers from storage, the stopper should be loosened or the container itself should be wrapped in towels and kept behind a shield. Dry ice can produce serious burns, as is also true for all types of dry-ice-cooled cooling baths.
Such as Ascarite® (sodium hydroxide-coated silica), should not be mixed with phosphorus pentoxide (P2O5) because the mixture may explode if it is warmed with traces of water. Because the cobalt salts used as moisture indicators in some drying agents may be extracted by some organic solvents, the use of these drying agents should be restricted to drying gases.
(C2H4O) has been known to explode when heated in a closed vessel. Experiments using ethylene oxide under pressure should be carried out behind suitable barricades.
That are suspensions of oxidizable particles (e.g., magnesium powder, zinc dust, carbon powder, and flowers of sulfur) in the air can constitute powerful explosive mixtures. These materials should be used with adequate ventilation and should not be exposed to ignition sources. When finely divided, some solids, including zirconium, titanium, Raney nickel, lead (such as prepared by pyrolysis of lead tartrate), and catalysts (such as activated carbon containing active metals and hydrogen), can combust spontaneously if allowed to dry while exposed to air and should be handled wet.
Such as chloroform (CHCl3), carbon tetrachloride (CCl4), and other halogenated solvents, should not be dried with sodium, potassium, or other active metal; violent explosions usually result. Many halogenated compounds are toxic. Oxidized halogen compounds—chlorates, chlorites, bromates, and iodates—and the corresponding peroxy compounds may be explosive at high temperatures.
(H2O2) stronger than 3% can be dangerous; in contact with the skin, it can cause severe burns. Thirty percent H2O2 may decompose violently if contaminated with iron, copper, chromium, or other metals or their salts. Stirring bars may inadvertently bring metal into a reaction and should be used with caution.
Open to the atmosphere condense liquid air rapidly. Then, when the coolant is removed, an explosive pressure buildup occurs, usually with enough force to shatter glass equipment if the system has been closed. Hence, only sealed or evacuated equipment should be so cooled.
(LiAlH4) should not be used to dry methyl ethers or tetrahydrofuran; fires from reaction with damp ethers are often observed The reaction of LiAlH4 with carbon dioxide has reportedly generated explosive products. Carbon dioxide or bicarbonate extinguishers should not be used for LiAlH4 fires; instead such fires should be smothered with sand or some other inert substance.
May be explosive, especially if more than one nitro group is present. Alcohols and polyols can form highly explosive nitrate esters (e.g., nitroglycerine) from reaction with nitric acid.
Are hazardous because some organometallic compounds burn vigorously on contact with air or moisture. For example, solutions of t-butyl lithium can cause ignition of some organic solvents on exposure to air. The pertinent information should be obtained for a specific compound.
Should be handled with care because serious explosions have resulted from contact between oil and high-pressure oxygen. Oil or grease should not be used on connections to an O2 cylinder or gas line carrying O2.
Are hazardous because some organometallic compounds burn vigorously on contact with air or moisture. For example, solutions of t-butyl lithium can cause ignition of some organic solvents on exposure to air. The pertinent information should be obtained for a specific compou
Used for hydrogenations should be handled with care behind a shield, and the operator should wear goggles and a face shield.
Are explosive when treated with sulfuric acid. If both compounds are used in an drying tube, an empty trap should be placed between them and monitored for entrapment.
should be avoided insofar as possible. Perchlorate salts of organic, organometallic, and inorganic cations are potentially explosive and have been set off either by heating or by shock. Perchlorates should not be used as drying agents if there is a possibility of contact with organic compounds or of proximity to a dehydrating acid strong enough to concentrate the perchloric acid (HClO4) (e.g., in a drying tube that has a bubble counter containing sulfuric acid). Safer drying agents should be used. Seventy percent HClO4 can be boiled safely at approximately 150 °C, but contact of the boiling undiluted acid or the hot vapor with organic matter, or even easily oxidized inorganic matter, will lead to serious explosions. Oxidizable substances must never be allowed to contact HClO4. This includes wooden benchtops or hood enclosures, which may become highly flammable after absorbing HClO4liquid or vapors. Beaker tongs, rather than rubber gloves, should be used when handling fuming HClO4. Perchloric acid evaporations should be carried out in a hood that has a good draft. The hood and ventilator ducts should be washed with water frequently (weekly; but see also section 8.C.7.5) to avoid danger of spontaneous combustion or explosion if this acid is in common use. Special perchloric acid hoods are available from many manufacturers. Disassembly of such hoods must be preceded by washing of the ventilation system to remove deposited perchlorates.
(inorganic) should be handled carefully. When mixed with combustible materials, barium, sodium, and potassium peroxides form explosives that ignite easily.
(P) (red and white) forms explosive mixtures with oxidizing agents. White phosphorus should be stored under water because it ignites spontaneously in air. The reaction of phosphorus with aqueous hydroxides gives phosphine, which may either ignite spontaneously or explode in air.
(PCl3) reacts with water to form phosphorous acid with HCl evolution; the phosphorous acid decomposes on heating to form phosphine, which may either ignite spontaneously or explode. Care should be taken in opening containers of PCl3, and samples that have been exposed to moisture should not be heated without adequate shielding to protect the operator.
(K) is much more reactive than sodium; it ignites quickly on exposure to humid air and, therefore, should be handled under the surface of a hydrocarbon solvent such as mineral oil or toluene (see Sodium). Potassium can form explosive peroxides on contact with air. If this happens, the act of cutting a surface crust off the metal can cause a severe explosion.
Have been known to explode when the still was vented suddenly to the air before the residue was cool. Such explosions can be avoided by venting the still pot with nitrogen, by cooling it before venting, or by restoring the pressure slowly. Sudden venting may produce a shockwave that can detonate sensitive materials.
(Na) should be stored in a closed container under kerosene, toluene, or mineral oil. Scraps of sodium or potassium should be destroyed by reaction with n-butyl alcohol. Contact with water should be avoided because sodium reacts violently with water to form hydrogen (H2) with evolution of sufficient heat to cause ignition. Carbon dioxide, bicarbonate, and carbon tetrachloride fire extinguishers should not be used on alkali metal fires. Metals like sodium become more reactive as the surface area of the particles increases. Prudence dictates using the largest particle size consistent with the task at hand. For example, use of sodium ''balls" or cubes is preferable to use of sodium "sand" for drying solvents.
(H2SO4) should be avoided, if possible, as a drying agent in desiccators. If it must be used, glass beads should be placed in it to help prevent splashing when the desiccator is moved. To dilute H2SO4, the acid should be added slowly to cold water. Addition of water to the denser H2SO4can cause localized surface boiling and spattering on the operator.
(Cl2CCHCl) reacts under a variety of conditions with potassium or sodium hydroxide to form dichloroacetylene, which ignites spontaneously in air and detonates readily even at dry ice temperatures. The compound itself is highly toxic, and suitable precautions should be taken when it is used.
(NaNH2) can undergo oxidation on exposure to air to give sodium nitrite in a mixture that is unstable and may explode.
