Initial nitrogen dioxide, effect

Nitrogen dioxide effectively reacts with various low- and high-molecular organic compounds [5-7, 31]. However, it must be emphasized that NO is a free radical of moderate reactivity, and the ONO-H bond strength [14] makes up 320 kJ mofr . Therefore, radicals NO are capable of initiating... 

Investigation into the effect has been mainly devoted to reactions with red fuming nitric acid . It seems that in red fuming nitric acid a preliminary reaction results in the formation of a surface deposit of finely divided metallic titanium ignition or pyrophoricity can then be initiated by any slight impact or friction. The tendency to pyrophoricity increases as the nitrogen dioxide content of the nitric acid rises from zero to maximum solubility at about 20%, but decreases as the water content rises, the effect being nearly completely stifled at about 2% water. 

Figure 15. Effect of dilution. In this calculation, the initial concentrations of propylene (0.2 ppm), nitric oxide (0.1 ppm), and nitrogen dioxide (0.005 ppm) are reduced by a factor of 10 from the reference concentrations.

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