kilowatt - 27-10-2007 at 01:15
How come red fuming nitric acid which I distilled from plumber's grade H2SO4 and potassium nitrate turns a blue-green color when dissolved into
distilled water at high concentrations? I have never observed the color fade at all until lower dilutions are reached, and then it goes away. Is
this from N2O3 somehow forming, or some impurity that got carried over from the sulfuric? The KNO3 was reagent grade. Distilled in a 24" reflux
still with fiberglass packing of all glass/teflon except for one small coupling made of clear PVC with very little contact to the acid.
woelen - 27-10-2007 at 06:44
It is the color of N2O3. A similar color is obtained, when sodium nitrite or potassium nitrite is added to icecold dilute sulphuric acid. A green
color is due to a mix of blue N2O3 and brown NO2.
Fleaker - 28-10-2007 at 14:10
Must've distilled at too high a temperature. I have had that happen to me as well.
kilowatt - 28-10-2007 at 19:56
Is the fact that overheating results in too high an NO2 content the problem here? I plan to go with vacuum distillation for fuming nitric, and just
aqueous nitric for general purpose, from now on.