Method for Azide Determination

To eliminate the problem caused by oxidation of the phlegmatizing agents, it is common practice to distill hydrazoic acid from the azide solution or slurry using perchloric acid. The hydrazoic acid (boiling point 35.7°C)is distilled into a known volume of standard ceric ammonium nitrate. The excess ceric ammonium nitrate is titrated with either standard ferrous ammonium sulfate or sodium 

Solution Required. A 0.1 N solution is prepared by dissolving 17.1 g of silver nitrate in chloride-free distilled water and diluting to 1 liter in a volumetric flask. The silver nitrate solution is standardized using accurately weighed 0.1-g portions of dried reagent-grade sodium chloride. The factor [F] is calculated from the chloride consumption. The standardized solution is stored in a dark bottle. 

Preparation. The silver nitrate is ground in a clean mortar, dried at 140-150°C for 2 hr, cooled in a desiccator, and immediately weighed. It is advisable to dry only sufficient material for the preparation of one lot of solution. The factor for the silver nitrate will not alter significantly over a period of one month, provided it is stored in well-stoppered, dark-glass storage bottles. 

Standardization. K 50-nil aliquot of the silver nitrate solution is added to 5 ml of concentrated nitric acid (free from nitrous acid) and 2 ml of a saturated solution of ferric alum. The silver nitrate solution is titrated with the ammonium thiocyanate solution until a fleeting reddish endpoint is reached. The strength of the ammonium thiocyanate solution is calculated from the titer. 

On completion of the determination, the silver azide on the filter paper must be destroyed as follows  

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