Explosives lead azide

Synonym(s) Lead metal plumbum olow (Polish) pigment metal Lead(2+) acetic acid plumbous acetate Initiating explosive (lead azide, dextrinated type only) Lead (II) bromide d... 

For the terrorist, TATP and HMTD offer easy sources of primary explosives. Consulting the do-it-yourself literature, it can be seen that there are two other commonly recommended primary explosives—lead azide Pb(N3)2 and mercury fulminate Hg(ONC)2, but these are difficult to prepare cleanly. The synthesis of diazodinitrophenol (DDNP) (Fig. 2.5), common in commercial detonators, is reported in such publications, but apparently is rarely attempted by clandestine chemists. Typically, the brisance of a primary is less than TNT, but the efficacy is the fact that a shock wave can result from a relatively mild insult. 

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]. 

Primary explosives (also known as primary high explosives) differ from secondary explosives in that they undergo a very rapid transition from burning to detonation and have the ability to transmit the detonation to less sensitive explosives. Primary explosives will detonate when they are subjected to heat or shock. On detonation the molecules in the explosive dissociate and produce a tremendous amount of heat and/or shock. This will in turn initiate a second, more stable explosive. For these reasons, they are used in initiating devices. The reaction scheme for the decomposition of the primary explosive lead azide is given in Reaction 2.2. 

In early days Alfred Nobel already replaced mercury fulminate (MF, see above), which he had introduced into blasting caps, with the safer to handle primary explosives lead azide (LA) and lead styphnate (LS) (Fig. 1.17). However, the long-term use of LA and LS has caused considerable lead contamination in military training grounds which has stimulated world-wide activities in the search for replacements that are heavy-metal free. In 2006 Huynh und Hiskey published a paper proposing iron and copper complexes of the type [cat]2[Mn(NT)4(H20)2] ([cat]+ = NH4, Na+ M = Fe, Cu NT = 5-nitrotetrazolate) as environmentally friendly, green primary explosives (Fig. 1.17) [3]. 

Physico-chemical and explosive properties of metal azides Opt ical properties Sli>w decomposition of a/ides Fast decomposition and explosion Lead azide... 

Among the initiating explosives lead azide is second in order of importance. It forms fine white crystals, but these tend to increase in site in contact with water and may explode spontaneously. On heating it explodes at 320 to 340. ... 

Of interest are some correlations which Cook tentatively established between theoretical detonation and explosion results and the practical performance of explosives. For a group of primary and near-primary explosives (lead azide, mercury fulminate, and six CHNO explosives), he found a correlation between the probable order of ease of transition from deflagration to detonation and adiabatic explosion temperature. Moreover, he noted a rough correlation between the effectiveness of a primary explosive as a detonator (its ability to transfer detonation to a secondary explosive) and the C-J pressure [130]. 

Silver azide, lead azide, etc., heavy metal azides are highly explosive. Lead azide is very sensitive for impact, so it is used as a detonator. Generally, other azides are nonexplosive. Sodium azide is most widely used. It is water decomposable, and the hydrolysis product is diazoimide (HN3). Aryl azides are colorful and relatively stable solids. They explode when being impacted, and decompose when being melted and release HN3. Sodium azide easily combines with lead or copper to produce metal azides, which are highly explosive. 

The most recent approach to the synthesis of DAT was made at LMU Munich [39,40] and eliminates the formation of highly explosive lead azide... 

Only relatively few compounds can act as primary explosives and still meet the restrictive military and industrial requirements for reflabiUty, ease of manufacture, low cost, compatibiUty, and long-term storage stabiUty under adverse environmental conditions. Most initiator explosives are dense, metaHoorganic compounds. In the United States, the most commonly used explosives for detonators include lead azide, PETN, and HMX. 2,4,6-Triamino-l,3,5-triuitrobenzene (TATB) is also used in electric detonators specially designed for use where stabiUty at elevated temperatures is essential. 

Lead Azide. The azides belong to a class of very few useflil explosive compounds that do not contain oxygen. Lead azide is the primary explosive used in military detonators in the United States, and has been intensively studied (see also Lead compounds). However, lead azide is being phased out as an ignition compound in commercial detonators by substances such as diazodinitrophenol (DDNP) or PETN-based mixtures because of health concerns over the lead content in the fumes and the explosion risks and environmental impact of the manufacturing process. 

In general terms, PETN can be characterized as a sensitive , brisant, and powerful high expl. Explosive sensitivity is a rather nebulous quantity, but there can be no doubt that PETN is a much more sensitive material than TNT, but rather less sensitive than Lead Azide. In particular, PETN requires very little priming i charge (less than 1 mg LA) to initiate its detonation. This is the characteristic that makes PETN so widely used in blasting cap base charges, in detonating cord and in boosters... 

Mechanical treatment alone may be sufficient to induce significant decomposition such processes are termed mechanochemical or tribo-chemical reactions and the topic has been reviewed [385,386]. In some brittle crystalline solids, for example sodium and lead azides [387], fracture can result in some chemical change of the substance. An extreme case of such behaviour is detonation by impact [232,388]. Fox [389] has provided evidence of a fracture initiation mechanism in the explosions of lead and thallium azide crystals, rather than the participation of a liquid or gas phase intermediate. The processes occurring in solids during the action of powerful shock waves have been reviewed by Dremin and Breusov [390]. 

The increase in volume as gaseous products are formed in a chemical reaction is even larger if several gas molecules are produced from each reactant molecule, such as the formation of CO and CO, from a solid fuel (Fig. 4.17). Lead azide, Pb(N3)2, which is used as a detonator for explosives, suddenly releases a large volume of nitrogen gas when it is struck ... 

Lead azide, Pb(N,)2, is used as a detonator, i i) What volume of nitrogen at STP (1 atm, 0°Ci does 1.5, of It id azide produce when it decomposes into lead metal and nitrogen gas (b) Would 1.5 g of mercury(ll) azide, Hg(N which is also used as a detonator, produce a larger or smallei volume, given that its decomposition products i c elemental mercury and nitrogen gas (c) Metal azides in general are potent explosives. Why ... 

Mass effects due to some ions in salts. It is generally observed that there is a greater instability amongst compounds containing heavy atoms compared with elements in the first periods of the periodic tabie.This can be observed by analysing enthalpies of formation of ammonia, phosphine, arsine and stibine (see previous table for the last three). In the same way, it is easier to handle sodium azide than lead azide, which is a primary explosive for detonators. It is exactly the same with the relatively highly stable zinc and cadmium thiocyanates and the much less stable mercury thiocyanate. 

Commercially, lead azide is usually manufactured by precipitation in the presence of dextrine, which considerably modifies the crystalline nature of the product. The procedure adopted is to add a solution of dextrine to the reaction vessel, often with a proportion of the lead nitrate or lead acetate required in the reaction. The bulk solutions of lead nitrate and of sodium azide are, for safety reasons, usually in vessels on the opposite sides of a blast barrier. They are run into the reaction vessel at a controlled rate, the whole process being conducted remotely under conditions of safety for the operator. When precipitation is complete, the stirring is stopped and the precipitate allowed to settle the mother liquor is then decanted. The precipitate is washed several times with water until pure. The product contains about 95% lead azide and consists of rounded granules composed of small lead azide crystals it is as safe as most initiating explosives and can readily be handled with due care. 

Lead styphnate is a poor initiating explosive which when dry is very sensitive to friction and impact, to electrostatic discharge, and to flame. Its main use is as an additive to lead azide to improve flame sensitiveness (see p. 101). When pressed to a density of 2-6 g ml-1 it has a velocity of detonation of4900 m s l. 

The original initiating explosive used by Nobel and all manufacturers for many years was mercury fulminate. This had the disadvantage of decomposing slowly in hot climates, particularly under moist conditions. For this reason mercury fulminate is no longer widely used. In most countries it has been replaced by a mixture of dextrinated lead azide and lead styphnate. In the U.S.A. some detonators are made containing diazodinitrophenol. 

The initiating explosive used must ignite with certainty from the spit of a safety fuse. It must be remembered that the intensity of the spit can be reduced if the safety fuse is not cut squarely and also that the fuse may in practice not always be fully inserted into the detonator. Lead azide by itself is not sufficiently easily ignited to give a satisfactory plain detonator and it is therefore used in admixture with lead styphnate, which is very readily ignited by flame. The proportions of such mixtures vary from 25 to 50% of lead styphnate. Mercury fulminate and diazodinitrophenol are sufficiently sensitive to flame not to require such additives. 

Although the requirement for flame sensitiveness is the main consideration for initiating explosives for plain detonators, others are important in manufacture. The explosive must be capable of compression into a coherent mass and at the same time leave the equipment free from adhesions. Lead azide can be somewhat deficient in cohesion, and to improve this a small proportion of tetryl is sometimes added to the... 

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 nitration product of perchloryl benzene is explosive, comparable in shock-sensitivity with lead azide, with a very high propagation rate. 

A solution, prepared by mixing saturated solutions of cadmium sulfate and sodium azide in a 10 ml glass tube, exploded violently several horns after preparation [1], The dry solid is extremely hazardous, exploding on heating or light friction. A violent explosion occurred with cadmium rods in contact with aqueous hydrogen azide [2], A DTA study showed a lesser thermal stability than lead azide [3], It is strongly endothermic (AH°f (s) +451 kJ/mol, 2.32 kJ/g). 

This unstable material usually explodes on vaporisation (at — 82°C) [1], It is extremely explosive in the liquid and solid states. A safe method has been developed for preparing the pine gas on 20 mg scale. It may be stored safely at 10-20 mbar/—80°C for several months. Cooling the gas to — 196°C, or evaporation of the liquid at a fast rate may lead to very violent explosions. Fluorine azide is now described as triazadienyl fluoride [2], as shown above. 

It is less sensitive and a less powerful explosive than silver azide or lead azide. It explodes on heating in air to above 270°C, or after an induction period at 140°C in the dark under vacuum. 

The endothermic nitride is susceptible to explosive decomposition on friction, shock or heating above 100°C [1], Explosion is violent if initiated by a detonator [2], Sensitivity toward heat and shock increases with purity. Preparative precautions have been detailed [3], and further improvements in safety procedures and handling described [4], An improved plasma pyrolysis procedure to produce poly (sulfur nitride) films has been described [5], Light crushing of a small sample of impure material (m.p. below 160°C, supposedly of relatively low sensitivity) prior to purification by sublimation led to a violent explosion [6] and a restatement of the need [4] for adequate precautions. Explosive sensitivity tests have shown it to be more sensitive to impact and friction than is lead azide, used in detonators. Spark-sensitivity is, however, relatively low [7],... 

An explosion occurred during blending and screening operations on a mixture of lead azide and 0.5% of calcium stearate. If free stearic acid were present as impurity in the calcium salt, free hydrogen azide may have been involved. 

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