nitrogen dioxide 
noun [mass noun] Chemistry
A reddish-brown poisonous gas formed when many metals dissolve in nitric acid.
- Chemical formula: NO2. It usually exists in equilibrium with dinitrogen tetroxide, N2O4.
- Increases in ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide are blamed primarily on the motorist.
- Free radicals such as nitric oxide and nitrogen dioxide show weak attractions toward magnetic fields - they are called paramagnetic.
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