Lead azide continuous method

THE CONTINUOUS METHOD OF LEAD AZIDE MANUFACTURE (ACCORDING TO MEISSNER [110, 111])... 

The method involves introducing a continuous supply of lead nitrate and sodium azide solutions in equivalent proportions into the upper part of the reaction column (Fig. 50) from the bottom of which a suspension of lead azide is removed. The reaction mixture flows down in countercurrent to air blown in. 

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

Bulk Density. Bulk density is determined by a method in which 1 g of lead azide is added incrementally to a vertical, graduated tube about 0.5 cm diam and partially filled with normal butyl alcohol. Particles adhering to the sides are washed down with butyl alcohol, addition of which is continued until the volume of material in the tube is exactly 5 ml. After standing 15 min without jarring or vibrating, the level of the lead azide column is read, calibration corrections applied, and the bulk density, calculated ftom the volume occupied, reported in g/ml. 

Another method for preparing the p-form is based on the reaction of lead nitrate and sodium azide, at room temperature and in the presence of organic dyes. When solutions of lead nitrate (20 %) and of sodium azide were run continuously into water at 20 °C only a-LA was observed, but if even as little as 0.02 % of eosin or other organic dye is present in the reaction mixture, the p-form appears. The crystals are best handled as single specimens as they are sensitive breaking one will set off the whole batch [16]. 

A method of preparing a reduced sensitivity SA introduced in USA is called the Costain process after Thomas Costain who improved the original procedure for RD 1336 developed in England in the ERDE laboratories shortly after World War 11 [96]. In the Costain process, aqueous solutions of silver nitrate and sodium azide are added to the dilute aqueous ammonia (or an aqueous solution of sodium azide is added to an aqueous solution of silver nitrate and ammonia). The reaction mixture is then heated and part of the ammonia is distilled from the solution. When the first silver azide precipitate appears, a small amount of acid (e.g., acetic acid) is added to induce crystal seeding and results in profuse nucleation ( shock crystallization ). The distillation of ammonia then continues and the precipitation of silver azide is total. Costain reported several improvements for his product, first of all bulk density 1.4 g cm [96]. Hirlinger and Bichay later reported a further improvement leading to a product with density 1.6 g cm [97] (vs. 1.0 g cm for original ERDE silver azide). Further, concentration and addition parameters are not as critical as for the ERDE process [96]. Not much has been published about the Costain process but some details have been published in [98]. 

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