SM2 - 10-7-2012 at 07:49
Perhaps a bit off topic, but I find it interesting that solutions of nitrous acid, are blue. The higher the conc. the acid, the bluer. Under
ordinary ambient environment, it is only possible to make a fairly dilute solution of HNO2-. Typically using dil H2SO4, and (aq) NaNO2. As the
concentration rises, the nitrous acid breaks down into nitric oxide and water, and you can even see the brown nitrogen dioxide as it is formed,
indicating concentration limit has been made. Of course, if you were to cool things down, my guess is you could make a more concentrated solution of
this weak acid, and the solution would be an even darker blue.
woelen - 10-7-2012 at 22:42
I split and moved this thread from the thread about making NaNH2. This subject indeed is off topic, but it is interesting on its own, so let's
continue in this thread.
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I think that the blue color is due to formation of N2O3 in equilibrium with HNO2:
2HNO2 <----> N2O3 + H2O
N2O3 has a deep blue color and this liquid can easily be made by putting a mix of NO and NO2 in a refrigerator. Some of the gas mix then liquefies and
forms a few drops of N2O3.