Hydrazoic Acid by Gas Chromatography and Other Methods

Determination of Hydrazoic Acid by Gas Chromatography and Other Methods 

Trace quantities of hydrazoic acid at levels of 10 M can be determined by gas chromatography [22], The sample is freeze-dried in alkaline media on a vacuum line, sulfuric acid is added to the azide sample without breaking vacuum, and helium is then used to sweep the hydrazoic acid through a Linde No. 5 molecular sieve powder, binder-free, packed in a 2-mm glass capillary column. The retention time for a 6-ft column and a 50 ml/min helium flow rate at ambient room temperature is about 15 min. A thermal conductivity cell with gold-plated filaments is used as a detector. 

As little as 1 mm of hydrazoic azid [23] in a volume of 250 ml has been determined on a vacuum line by passing the hydrazoic acid through a packed tube of ceric ammonium nitrate, which had been evaporated on an asbestos fiber substrate, dried, and ground with mortar and pestle. The packing effectively reduced hydrazoic acid to nitrogen, which can be measured on a calibrated Toepler-McLeod gauge. 

Both the above techniques require standardization using a known quantity of sodium azide carried through the same procedure. A semimicro gas-evolution method has been described by Blais [24] which utilizes only a few milligrams of lead azide. Nitrogen is determined by reduction of hydrazoic acid with heated cupric oxide. 

A Kjeldahl procedure which reduces the azide ion to ammonia followed by colorimetric determination of the ammonia has been described [25], 

---