Posts Tagged ‘blue’


August 31, 2011

A fun couple of days all in! (28-29th July 2011)

So for night time I decided to indulge in a guilty pleasure, and just drive off into the quiet forests of Oregon, and just, well, sleep!  Well mostly sleep.  I did leave a timelapse going of the milky way from the forests of Oregon…. Pretty!

The next morning I was up early, and spent it bumming around crater lake.  When I first got the lake, it was mirror still!  It’s rarely that still at crater lake (normally wind disturbs the surface, as it had does by the end of this timelapse), so I set up the camera… more pretty!

While that was going down, I got accosted by one of the GIANT VOLCANIC CHIPMUNKS that roam the area!

And boy did that 4.5mm sigma 180 degree fisheye lens earn its keep at crater lake.  Y’see Crater Lake is just so big by the time you can see it, basically only a 180 degree lens will get it all in!

A keep back sign? Now that's just being a 'cliff tease'. Seriously though, these signs litter Crater Lake, which to be fair has a lot of cliffs, but does it really need all the idiot warning for people too stupid to spot poor footing and a terminal drop off?

and these ‘keep back signs’ litter the area in a way that smells of ‘frivolous lawsuit evasion’, or maybe it’s just to keep the number of Darwin Award winners from Crater Lake down.

Spent that evening on top of Mount Scott, well actually a rocky outcrop you have to climb up on near the top of Mnt Scott.  But the views were amazing. Just sat there and watched the sun go down over the lake!

Thunderf00t on mnt Scott looking down on crater lake. And yes, its about a 50ft drop off that rock! Mnt Scott is the highest point in Crater Lake NP. The actual summit has a fire lookout built on it and smells of urine. However for those willing to do a little hand n foot scrambling, there are a couple of satellite summits that have amazing views.

Spent the early evening helping doing some astronomy outreach (of a sort).  Skies were dark, but a little murky.  Had the scope catching photons from the M101 supernova till about 2am before packing up.  However Jupiter rising over the lake gave some captivating specular reflections!  Left the timelpase running till about 4am, would have been longer, but I feel asleep before changing the battery.  Damn my intolerance to sleep deprivation!

Next morning, a very tired Thunderf00t decided the air was still enough to take to the skies, using the helmet of doom!  Here I was alternating between first person flying, and flying by direct sight.  It’s really ballsy stuff in that by the plane has to be quite close (relativley) to fly by direct sight, and if you go further, you are 100% reliant on the video and RC gear working.  There is also the problem that by the time the plane is so far away, that you cannot see it, the plane also cannot see you!  So bascially you have to navigate by big cliffs and the sun to find your way home.  The bottom line is, while the plane was almost beyond the point where you could see it to fly it, it still didn’t make it over the lake.

After that little adrenaline rush I was ready for some excitement, which came in the form of swimming in an ice-cold lake formed by a collapsed volcano!

and yeah that water looks perty and blue, its just as amazingly blue when you get your head under it!  Regrettably, by the time I’d worked that out, I’d left the contraption for getting the camera underwater (a sort of ziplock bag) back in the car, 1000 ft above me on the crater rim 😦


Why is Potassium gas Green?

June 18, 2011

So my interest was really spiked here when I found that when reacting with water, potassium gives off a green gas!

While the green of potassium gas has been known about for over a century, being found in Encyclopedia Britianica articles as far back as 1911, the origin of that green color is proving a little more elusive.

If you know what you are doing it’s relatively easy to observe.  250 mg of potassium is ‘the right’ scale to work with.  Much smaller and it’s all over before you get a chance to do anything, much bigger and you run into problems with the metal exploding, or the hazards of hydrogen build-up.  All you need is a heavy glass vessel of about the dimensions of a wine glass.  Insert a burning acetone taper through a small hole in the top of the vessel and to burn out all the oxygen, and then drop in your potassium.  The green color is easily visible.

I’m tempted to propose it’s due to the solvated electron, which is a hot research topic at the moment as it’s part of the principal mechanism by which radiation damage happens to DNA.  It’s known to be stable and blue in liquid ammonia, but survives only picosecond in water.

A bead of Sodium Potassium alloy in anhydrous liquid ammonia. The blue colouration is due to the presence of solvated electrons

It’s an interesting suggestion, but I think the observation that you get the green color when there is no water around pretty much kills this idea.

So how do you get a green gas.  Well the only other metallic gaseous vapor I’ve seen was mercury which I once boiled to test the calibration on a thermocouple.  That has no color at all that I can remember.

Well as you will recall virtually all the gases are colorless, e.g. all the Noble gases (helium, argon etc) and all the first period gases (nitrogen, oxygen, and mostly fluorine).  However the heavier halogens have colored vapors that get more heavily colored as you go down the group.  Chlorine, light green, bromine, brown etc.

Chlorine (left) and bromine (right).

The reason these gases have these colors is the same reason the sky is blue, Rayleigh scattering.  That’s related to the polarizability of the molecule.  This is a very different mechanism from the electronic transitions that give the classical flame colors of the alkali metals!

It’s well known that all the alkali metals have stable bound states as diatomic molecules, similar in electronic configuration to hydrogen.  IF K2 had a similar polarizability to Cl2, it may well be green like chlorine!  Regrettably finding the polarizability K2 is not as easy as it sounds.  A significant difference between H2 and K2 is the bond energy.  H2 has a bond energy of about 400kJ/mol, while K2 has a bond energy of ~50kJ/mol.  For reference, the hydrogen bond, the thing that holds water together as a liquid, has a bond energy of ~20kJ/mol.  If you heat any bound state and eventually the species will gain enough energy to separate and become individual species.  With water this happens at about 100 oC (boiling, ~400 K).  For hydrogen it’s about 3000 K.  You can actually do the real calculations, it’s just I’m too lazy at the moment, and so I’m just going to do a linear extrapolation between these two.  That gives K2 breaking up at about 2-300 oC.

Well that would fit nicely with green gas being evolved at lower temperature, but as the temperature rises, the diatomic species break up, and the relevant polarizability of the molecule, and hence the Rayleigh scattering, and hence the color is lost.

Great, so if this is a working hypothesis, then the diatomic metals should match their corresponding halogen right?  The bummer is sodium.  Sodium gives off a blue vapor when it boils.  Fluorine is almost colorless.  ARSE!

The game is not over yet!

I’ve decided I need to see sodium vapor for myself, but how to do it with only the junk I have to hand!  What I really need is a nice small sealed silica tube that can take temperatures over a thousand degrees C.  Hmmmm, thinking, thinking…..