Nitric acid, HNO3, and its derivatives

Nitric acid is an important industrial chemical (see Box 15.8) and is manufactured on a large scale in the Ostwald process, which is closely tied to NH3 production in the Haber-Bosch 

The industrial production of nitric acid (scheme 15.113) is carried out on a large scale and its manufacture is closely linked to that of ammonia. About 80% of all HNO3 produced is destined for conversion into fertilizers, with [NH4][N03] being a key product  

The commercial grade of [NH4][N03] contains 34% nitrogen. For fertilizers, it is manufactured in the form of pellets which are easily handled. Its high solubihty in water ensures efficient uptake by the soil. 

Ammonium nitrate has other important applications about 25% of the manufactured output is used directly in explosives, but its ready accessibility makes it a target for misuse, e.g. in the Oklahoma City bombing in 1995. The potentially explosive nature of [NH4][N03] also makes it a high-risk chemical for transportation. 

The explosive decomposition of ammonium nitrate. Charles D. Winters Science Photo Library 

Nitric acid is an important industrial chemical and is manufactured on a large scale in the Haber-Bosch process closely tied to NH3 production the first step is the oxidation of NH3 to NO (equation 14.21). After cooling, NO is mixed with air and absorbed in a countercurrent of water. The reactions involved are summarized in scheme 14.109 this produces HNO3 in a concentration of a 60% by weight and it can be concentrated to 68 % by distillation. 

N2O4 + H2O HNO3 + HNO2 2HNO2 NO + NO2 + H2O 3NO2 + H2O 2HNO3 + NO 

Pure nitric acid can be made in the laboratory by adding H2SO4 to KNO3 and distilling the product in vacuo. It is a colourless liquid, but must be stored below 273 K to 

An azeotrope is a mixture of two liquids that distils unchanged, the composition of liquid and vapour being the same. Unlike a pure substance, the composition of the azeotropic mixture depends on pressure. 

In aqueous solution, HNO3 acts as a strong acid which attacks most metals, often more rapidly if a trace of HNO2 is present. Exceptions are Au and the platinum-group metals (see Section 22.9) Fe and Cr are passivated by concentrated HNO3. Equations 8.8-8.10 illustrate HNO3 acting as a base. 

2NO + 02 2NO2 2NO2 N2O4 N2O4 + H2O —HNO3 + HNO2 (15.116) 

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Nitric acid (HNO3) assumed a central role among chemicals with applications in munitions, because all modern gunpowders and explosives are nitric acid derivatives. It became clear even before the transition to positional warfare that the 600 tons of explosives and 475 of gunpowder per month called for in the mobilization plan were amounts far too little to conduct the war, but even then the kinds and amounts that would be necessary on a regular basis remained unclear. For a time each arm had to make a new monthly calculation. The dimensions of the problem become clear if one reckons the quantity of nitrogen to which the army and navy... 

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