This question has been itching at me for the last couple months, so I'll ask here.
Are there any gases that are blue?
There are many colorful gases, chlorine, bromine, iodine, NO2, just to name a few, but I've never seen or heard of actual blue gases.Etaoin Shrdlu - 10-5-2014 at 20:20
Ozone.Chemosynthesis - 10-5-2014 at 20:36
^ This. Also, if you mean fluid, liquid oxygen can be a pale blue as well, though that is obviously not gaseous.numos - 10-5-2014 at 20:49
Is it possible to create a concentration high enough to see? I imagine it would be well after the lethal concentration.kristofvagyok - 11-5-2014 at 02:49
Well, ozone is not really blue when it's a gas. It could be blue, but such high concentrations are hard to produce. But when it's condensed and it is
in liquid form it is blue!
in the Dictionary of Organic Compounds, Volume 13, page 3461 they explained that hexafluorothioacetone is highly reactive towards nucleophile and
dienophile. it is a deep blue liquid or gas.
Nitrosyl cyanide ONCN is a green/blue gas (cyan). I once tried to make this by leading ONCl over humid AgCN (which I prepared by adding a solution of
AgNO3 to a solution of KCN), but I did not manage in making any blue gas. The ONCl did react with the AgCN, giving a dark brown solid, but no trace of
any blue gas could be observed.
CF3NO is a pure blue gas. Making this most likely is beyond the reach of nearly all amateurs.
I have made quite a few colored gases:
NO2 brown
Br2 (vapor) red/brown
ONCl orange
ONBr chocolate brown
Cl2 pale green/yellow
ClO2 intensely deep yellow
NbCl5 (vapor at 250 C or so) golden yellow
VOCl3(??) (vapor at 200 C or so) green
CrO2Cl2 (vapor) orange/red
I2 (vapor) purple
IBr (vapor) deep red
ICl (vapor) brown
BrCl golden yellow
Up to now, I never managed to make, nor have I ever seen in real life, a blue gas.
[Edited on 11-5-14 by woelen]Morgan - 12-5-2014 at 17:14
I once ground some iodine and ammonium nitrate together in a mortar and pestle, a few tablespoons worth, and then quickly mixed in some zinc dust
creating a column of billowing smoke about 7 feet high in the still air. It was so pretty and transitioned from a billowing blue column to an
intensely violet column of smoke. Maybe cooling caused the subtle transition, but it was something that has always stuck with me, how the one color
mysteriously transmogrified into the other, and the brief reference point of a blue wavelength became a vivid violet, as if you were trying to hang on
to a thought but couldn't.
So I started to wonder if iodine by itself could produce a true blue gas color instead of the above mixed particulate cloud and came across this which
I'm not sure about. The books were published long ago, 1885 and 1903.
"The vapor has a violet color when mixed with air. When in pure condition it is intensely blue."
"When mixed with air ... but the pure vapor is deep blue"
sounds like you made alot, morgan..? and sounds like a very interesting somewhat OTC mixturewoelen - 13-5-2014 at 02:34
The effect Morgan describes also is known in solution.
If you dissolve KMnO4 in water, then at great dilution, the liquid is pink, when it becomes more concentrated it becomes reddish at first, but the
more concentrated it is the more purple it becomes and at concentrations where it is nearly black, light going through the liquid looks blue.
I think that this effect is due to absorption both in red and in blue parts of the spectrum, with stronger absorption in the red part. At higher
concentration, you only see the blue part of the light and the liquid seems blue. With iodine vapor this effect also exists. Iodine vapor is
remarkably dark and even in a test tube, which is heated quite well, such that a lot of iodine vapor is in it, the effect can be observed. I would
not, however, call this vapor blue at such high concentrations.unionised - 13-5-2014 at 12:20
Well, it could be this sort of thing http://en.wikipedia.org/wiki/Dichromatism
and there's another possibility. Very hot I2 will dissociate to single I atoms.
Anyone know what colour that vapour would be?
(Incidentally, to me is sounds like a rather dangerous OTC mixture.)phlogiston - 14-5-2014 at 08:22
The color of sodium fluorescein solutions is also dramatically concentration-dependent. Concentrated solutions are brownish red, similar to the dry
powder, which changes to a very intense fluorescent yellow upon dilution.
At high concentrations, fluorescein molecules in the vicinity can re-absorb the emission due to fluorescence.
In other molecules, the formation of dimers (or other multimers) at high concentrations can also sometimes cause these kind of color changes.
No idea though what mechanism is behind iodine vapour and KMnO<sub>4</sub> thoughclearly_not_atara - 13-3-2020 at 19:31
"Chromium tetrafluoride is a glassy solid which forms blue vapours when heated."
