The Nitrogen-Oxygen System

Analysis of the works in which NO formation is studied [157] in the nitrogen-oxygen system at high temperature shows NO concentrations ranging within 2-4%. 

TABLE 2-235 Liquid-Vdpor Equilibrium Data for the Argon-Nitrogen-Oxygen System... 

The free radical nature of the nitric oxide molecule allows it readily to form association products with other free radicals. Both the nitroxyl radical (HNO) and nitrogen dioxide (NO2) may be regarded as simple association products of this type, and the high reactivities of both these species towards H, OH or O are able to produce several interesting and important effects when one of the two nitrogen oxides is added to, or formed in, the hydrogen—oxygen system. 

In this sub-section it is proposed to deal first with effects of oxides of nitrogen in the oxidation of carbon monoxide, in a manner similar to that adopted for the hydrogen—oxygen system. Following this the reactions with fluorine, fluorine monoxide and sulphur dioxide will be considered. 

In their work on the explosive oxidation of ammonia, which has already been discussed earlier, Husain and Norrish also examined the hydrazine system. Their principal results, obtained by the method of flash photolysis and kinetic spectroscopy, were as follows (a) no induction period was observed (b) NH emission, observable in the photolysis of pure N2H4, was visible at the shortest delay times (c) NO and OH were produced as the NH was decaying d) NO added to the hydrazine-oxygen system did not disappear in the combustion ( ) NO represented only about 5 % of the final products. Since, unlike the oxidation of ammonia, the major nitrogenous product is N2 rather than NO, Husain and Norrish concluded that reaction (15 ) is not a part of the main reaction sequence. They felt that the N-N bond was not split in in the main chain propagation. They proposed a mechanism involving nitrosamine, NH2NO, as a chain carrier viz. 

In these new radicals, the unpaired electron does not participate in multiple bond systems and, therefore, it is essentially localized at the nitrogen-oxygen bond (1,2). 

In terms of carbon-residue formation (Table II), heat-resistant polymers containing aromatic and heterocyclic units such as polyquinolines and po-lyquinoxalines have a strong tendency to form large condensed systems during pyrolysis and will finally carbonize (36). Formulas that include the occurrence of smaller polynuclear aromatic hydrocarbon systems in asphaltenes are consistent with such behavior when the majority of the nitrogen, oxygen, and sulfur species accumulate in the nonvolatile residue. 

During the course of an experimental study of the liquid-vapor equilibria of the nitrogen-oxygen-argon system ], it was found desirable to develop a rapid and accurate method for the analysis of equilibrium samples. After consideration of a number of possible analytical methods, such as chemical reactions for nitrogen and oxygen P or mass spectrometry [ ], gas chromatography was selected as the most likely to provide an acceptable technique. 

With the use of our analysis apparatus which could detect a condensable impurity in hydrogen down to 0.5 ppm, we could not find any measurable solubility of oxygen in liquid hydrogen. Conditions for these tests were identical with those for the nitrogen-hydrogen system. 

The experimental data for the methane-oxygen system, as well as the results of the work of Fastovskii and Krestinskii, are presented in Figure 5, Close agreement between the two sets of data can be observed. The methane-oxygen system approximates ideality in its behavior, as is shown by the computed solubility curve. This computation is based upon a Raoult s law ideal solubility equation, referred to later. Observations have not been made on the system below the freezing point of nitrogen. The portion below -345 F is based upon an assumption of ideality, which is apparently a reasonable one for this system as later discussion will also bear out. 

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