Lead azide neutral

Lead azide is manufactured on a technical scale by the action of sodium azide on an aqueous solution of lead nitrate. According to a description of manufacture in the Wolfratshausen factory in Germany [109], the reaction is conducted in an open reactor of stainless steel, provided with a jacket warmed by hot water and a stirrer which may be lifted out of the reactor (Fig. 49). The reactor is emptied by tilting. Its upper edge is therefore fitted with a spout so that the contents pour easily. The size of the reactor is such that 4.5 kg of lead nitrate in the form of a 9-10% solution can be used in each batch. This solution is poured into the reactor, warmed to 50°C and neutralized with sodium hydroxide to a pH of about 4.0 (in the presence of methyl orange) and 150 g of dextrin mixed with a small amount of water, is added. The suspension or solution of dextrin in water should be decanted before use to separate mechanical impurities, such as sand. 

The reaction is complete when no more ammonia is evolved. The product, which consists of an equimolecular mixture of sodium hydroxide and sodium azide, may be taken up in water and neutralized carefully witli nitric acid, and the resulting solution may be used directly for the preparation of lead azide, or the product may be fractionally crystallized from water for the production of sodium azide. The same material may be procured by washing the product with warm alcohol which dissolves away the sodium hydroxide. 

Neutral azide Basic azides Lead azide manufacture... 

In this method the lead azide is stored in solution form. To re-form lead azide, the solution is neutralized with nitric acid to destroy the plumbate ion complex, the phlegmatizing agent is added, and the pH is lowered until lead azide precipitates. A flow diagram for Richter s proposal is presented in Figure 2. 

Lead azide exists as four polymorphic forms [287] of which the orthorhombic oc-lead azide is the most stable [276]. In fact, a-lead azide is the only acceptable form for technological applications. Presently, the state of the art of making the polymorphs can be summarized as follows a-lead azide is the main product of precipitation, with traces of the other forms present [288]. The monoclinic [276] /3-form is stable when dry, but re crystallizes as the a-form [276,289]. The presence of organic dyes (eosin, neutral red) at the precipitation enhances formation of /3-lead azide [276] the presence of hydrophile colloids inhibits it [276,287]. The monoclinic [287] 7-form, apparently less stable than a and /3 [289], is obtained from pure reagents at a pH of 3.5-7 [287] or in the presence of polyvinyl alcohol [289]. The triclinic 6-form precipitates from pure reagents between pH 3.5 and 5.5 [287]. No method is presently available to yield a single polymorph exclusively, but the crystals differ sufficiently in shape to allow hand selection under the microscope [287,288]. 

Basic azides of various (OH) contents have been described, displaying less explosive power than lead azide. The compound (OH)Pb(N3), for example, merely deflagrates. It was made by Wohler and Krupko by way of hydrolysis Air was bubbled through a hot suspension of lead azide in water until the expelled HN3 had neutralized, via titration, the calculated amount of the base [176]. 

Lead is often found at low concentrations in neutralents. It may derive from munition components such as solder or from detonating compounds such as lead azide. Lead compounds are strong neurotoxins and have been associated with developmental mental retardation in children. Like other divalent metal cations (e.g., zinc and cadmium), lead(II) salts can be removed from aqueous streams by precipitation with sulfide or by ion exchange. 

The reaction of dicarbonyl(t 5-cyclopentadienyl)-carbyne complexes Cp(CO)2-n(PMe3)nMsC-R (M = Mo, W n = 0, 1 R = Me, Ph, Tol) with azides, N3R (R = CO2CH3, CH2CO2CH3), results in a [3+2]-cycloaddition to the electron rich metal carbon triple bond, leading to neutral 1-metalla-2,3,4-triazole complexes in high yields [43,44]. 

In figure 12, 13 and 14 the initial emission spectra of silver azide, lead styphnate and lead azide, respectively, are displayed. A continuum emission is observed with self-absorption (line inversion) at the positions of 328.1 nm and 338.3 nm emission of neutral silver atoms (see figure 12) and at 357.3, 364.0, 368.3, 374.0, and 405.8 nm... 

Structure modifiers was tested for modification of the crystal form of precipitated LA. The most commonly noted ones include dextrin, carboxymethyl cellulose, and PVA. The presence of dextrin promotes formation of the ot-form [16] while the presence of organic dyes (eosin, erythrosin, or neutral red) at precipitation time enhances the formation of the p-form [15]. The crystals of p lead azide are formed in the shape of long needles (Fig. 4.1). 

Insensitive to impact, it decomposes, sometimes explosively, above its m.p. [1], particularly if heated rapidly [2], Although used in aqueous solutions as a preservative in pharmaceutical preparations, application of freeze-drying techniques to such solutions has led to problems arising from volatilisation of traces of hydrazoic acid from non-neutral solutions, condensation in metal lines, traps or filters, and formation of heavy metal azides in contact with lead, copper or zinc components in the drying plant [3,4],... 

Substituent effects on ks. The replacement of an a-methyl group at the 4-methoxycumyl carbocation CH3-[14+] by an a-ester or a-amide group destabilizes the parent carbocation by 7 kcalmol-1 relative to the neutral azide ion adduct (Scheme 11 and Table 3) and results in 5-fold and 80-fold decreases, respectively, in ks for nucleophilic addition of a solvent 50/50 (v/v) methanol/water.33 These results follow the trend that strongly electron-withdrawing substituents, which destabilize a-substituted 4-methoxybenzyl carbocations relative to neutral adducts to nucleophiles, do not lead to the expected large increases in the rate constants for addition of solvent.28,33,92-95... 

As this soln is usually acidic (pH 4.2-4.6), add slowly 25 to 30 g NaOH in dil aq soln. NaOH serves to neutralize all acid either occluded or that due to hydrolysis of lead nitrate. An excess of NaOH must be avoided because it tends to produce elongated crysts of LA which are very sensitive. Add to the stock soln 9 lb(ca 4.08 kg) potato dextrin previously dissolved in about 100 1 of water and then bring the soln to 7.325 0.07% Pb (NOj)a content. b)Prepare the stock soln B by diluting with treated w the refined solution (contgca 27% NaNs),delivered from the Sodium Azide (qv) plant to 3.175 ... 

Isodrin (56) gives with f-butyl azidoformate an isolable triazoline (addition in position QQ) which decomposes into aziridine by chromatography over neutral alumina. 55 With tosyl azide, on the other hand, only the aziridine derivative could be isolated. Both aziridines undergo a series of transformations leading to a so-called bird-cage hydrocarbon 57. ... 

The use of Pd/C (87,89), neutral Raney Ni (W-2) (91,95), and Lyndlar s catalyst (90) have been reported in literature. Conditions used for the reduction of glycosyl azide have to be carefully optimized in order to suppress anomerization and the formation of undesired a-glycosides. Use of basic conditions and procedures that avoid noble metals leads to decreased a-glycosides formation (94). 

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