1 Lead Azide Purity

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],... 

Our new method of isolating sodium nitrotetrazolate dihydrate produces material in high yield, without the intermediate handling of sensitive explosive compounds. This produced NaNT is of sufficient purity for the preparation of DBX-1 of the quality that is required to replace lead azide. However, it does appear that the DBX-1 used as a seed crystal in the synthesis of DBX-1 influences the behavior of the end product. 

Lead azide with a purity of more than 95%... 

Pure lead azide may be produced in the same equipment, but instead of lead nitrate and dextrin lead acetate is employed. The precipitation temperature is lower than in the manufacture of technical-grade lead azide (having a purity of less than 95%). All other operations are the same as already described. 

The overall pptn time cycle is 60 mins,and 7.6 lbsLA(92.3% purity) is produced per pptn Analytical procedures for plant control and for finished products are described under Lead Azide, Analytical Procedures and under Sodium Azide Analytical Procedures... 

CoUoidaV lead azide. This is a pure fomi of lead azide (over 99% purity) in fine particles of 3-4 m. It is non-hygroscopic but not readily pourable and hence less adaptable for mass production. It is particularly sensitive to electric discharge and hence used for electric detonators. For tliis purpose colloidaf lead azide is often mixed wdth a concentrated nitrocellulose solution in ethyl ether-ethanol or oilier solvents. 

The continuous method of lead azide manufacture (according to Meissner) Lead azide with a purity under 95%... 

Purity. In this determination [7] the volume of gaseous nitrogen liberated by treatment of the lead azide with ceric ammonium nitrate is used to calculate the weight, reported as percentage, of lead azide in the test sample. 

As originally indicated by direct observation, decomposition can be described simply by a contracting envelope model. It seems unlikely that curve-fitting based on detailed kinetics data will provide much further insight into reaction mechanisms unless careful control is made of such factors as particle size, purity, and defect content. The recent results for lead azide suggest that many of the anomalies disappear when particle size is taken into account. It would be interesting to discover how many of the discrepancies in behavior, previously reported by different workers on the same material, could be resolved by closer attention to this single factor. 

The tin azide 11 (Scheme 16) is an example of a fluorous reagent that, unlike the fluorous tin hydride 1, transfers the fluorous tag to the product. This type of phase switch is very powerful only the nitrile that reacts with 11 is switched to the fluorous phase whereas any unreacted nitrile or impurities are left behind in the organic phase. Cycloaddition reaction of 11 with excess nitrile leads to fluorous tetrazoles 12. Again, BTF is a unique reaction solvent that serves to dissolve all reactants. Purification is effected in the usual way via fluorous-organic extraction. Deprotection yields the tetrazoles 13 in good yields and purities. 

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