Preparation and Reactions of Dinitrogen Tetroxide

Dinitrogen tetroxide and nitrogen dioxide exist in equilibrium  

The gas mixture becomes darker as the temperature is raised (the equilibrium shifts to the right). Tbe gas mixture can be obtained by heating heavy metal nitrates e.g. 

By passing the gases through an ice/salt freezing mixture ( 23% NaCl) liquid N2O4 can be obtained. Since the gas and the liquid are reactive towards H2O, the apparatus used should be dry and the powdered Pb(N03)2 should be previously dried. 

Since the gas and liquid are poisonous and since the liquid is corrosive, the preparation should be carried out in the fume cupboard and the gases should not be breathed in and the liquid should not come in contact with your skin. Since the gas and liquid attack rubber, an all glass set up has to be used with ground joints lubricated by silicone grease. 

Using a teat (Pasteur) pipette, add some drops of the liquid to about 3 cm distilled water and note any colour or temperature change. Divide the solution into 3 parts add to one part a few drops of universal indicator add to another part FeS04 solution and then gently warm. Boil gently the third part and then cool and add a little Cu metal and warm if necessary. Draw your conclusions. 

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