Sunday 31st (Sodium Boom n beyond)


Spent the morning very happily going over the potassium footage.  The whole thing is a symphony of physics and chemistry that eventually I decided it would take too long to explain, so I just put up the explosion footage.

It had been raining in Ridgecrest and this clearly was  a freak event.  The standard greeting in Rigercrest between the notably fat folks seems to be ‘hot enough for you’, and not without reason, I think it’s been over 100C every day I’ve been here.  However for the afternoon I decided I would give blowing up the sodium a go.  Now I have lots of sodium, and the scale and geometry is different.  Eventually I decided the way to do it was to get a stick over a reasonable sized vat, which meant that I could lift up the sodium from a distance, have it swing over the vat, then be lowered in.  Sodium is significantly less dense than water, and so would need to be weighted.  The sticks were typically about 10g, so eventually I wrapped up about 4 sticks in aluminium foil, attached weights to them and lowered them in to the vat from a distance.

Initially the reaction seemed really quite slow, to the point where I was wondering how this was going to pan out.  Indeed it took over 10 seconds before the first ‘explosion’ (compared to about 1second for the potassium experiment).  I, for my part am mostly certain this is related to the metal boiling.  However, when it really blew up (and did so quite convincingly) it really made a mess of the container.  Again, the hydrogen burning wasn’t really even a relevant factor, it’s just the adiabatic expansion of the gas released by the reaction.  In this case 40g gives about 40L of gas.  Thats a lot of gas to release in a 5L container!  On inspecting the aftermath it became clear that large chunks of sodium had been thrown clear of the reaction, not just unreacted, but unmelted!  This for me was a stunning observation!  It shows that whatever the reaction that takes place, the rate that heat is generated at the surface is MUCH higher than the rate the heat can be conducted away from the surface.  Sodium is an absolute bitch for making a mess!  Small amounts of sodium had been sprayed all over the tripod, and stripped the paint.  They had then picked up water to make conc. NaOH, draincleaner which will first turn you skin into soap, before chemically burning you.  The stuff was everywhere!  Cleaned up as best I could (again I was on the inaccessible dirt road to nowhere in my little ravine).  Headed back to LA.  Stopped off to see Lisa n Howard n pick up a shower, which I more than needed.  Initially i wanted to get up onto mnt Wilson early, for sunset, but got chatting to Lisa and that never happened.  It was full dark before I set out on the nightmare trek across LA by dark.  It didnt help that I managed to set the GPS wrong, and ended up on the long drive through the horrific twistiy winding roads of the Wilson range (rt 2).  There had been rain here too, and while the road was all but deserted, top speed was about 40 mph and ‘tire killing rocks’ materialized out of the gloom on a regular basis.  Driving that 20 miles was an incredibly intense experience, ultimately driven by ‘do u want it or not’.  I did, I wanted to get up on mnt wilson and do something on light pollution and LA.  I got there about midnight, and got my piccies!

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