Sodium Nitrate Specification Requirements

Lead azide is produced as a white precipitate by mixing a solution of sodium azide with a solution of lead acetate or lead nitrate. It is absolutely essential that the process should be carried out in such manner that the precipitate consists of very small particles. The sensitivity of lead azide to shock and to friction increases rapidly as the size of the particles increases. Crystals 1 mm. in length are liable to explode spontaneously because of the internal stresses within them. The U. S. Ordnance Department specifications require that the lead azide shall contain no needle-shaped crystals more than 0.1 mm. in length. Lead azide is about as sensitive to impact when it is wet as when it is dry. Dextrinated lead azide can apparently be stored safely under water for long periods of time. The belief exists, however, that crystalline service azide becomes more sensitive when stored under water because of an increase in the size of the crystals. 

The USA Military Specification (Ref 8) contains the following chemical criteria and requirements (1) As2Os by sodium thiosulfate—iodine titration 99.0% min, (2) As203 by carbonate-iodine titration 0.05% max, (3) Cl as AgCl turbidity 0.005% max, (4) heavy metals as PbS turbidity 0.010% max, (5) Fe as a Fe(CNS)3. 9KCNS.4H20 red coloration 0,010% max and (6) nitrate as an indigo carmen blue coloration which persists for over 5 mins... 

Elemental compostion Ce 25.56%, H 1.47%, N 20.44%, 0 52.53%. The aqueous solution of the compound may be analyzed for Ce by AA or ICP spectrophotometry. Also, the solution may be measured for NH4 ion by ammonium ion-selective electrode and the NO3 ion by nitrate ion-specific electrode, ion chromatography or cadmium-reduction colorimetry. For all these measurements, the solution may require sufficient dilutions. For quantitation, its solution may be standardized by titration with a reducing agent such as sodium oxalate in the presence of iron and ferroin indicator. 

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