/sci/ what colour should be concentrated >98% nitric acid? For last few months each batch I get from my supplier has a greenish/ mint colour. I thought it is due to some amount of dissolved N2O3 which when combined with yellowish/brown NO2, would give the green colour. But when I tried to remove the dissolved oxides by bubbling air through the acid and simultaneously heating, nothing really changed. The acid was fuming white slightly more intense but the fumes didn't turn brown in air, so I guess it is low in dissolved oxides.
The only other possibility that I can figure out is contamination with copper, nickel, iron or chrome ions.

What do you think, /sci/?