RE: What's the sodium for?

[Robert Myers <rmyers@inetone.net>]

>I do believe the sodium is either a powder or a liquid, tho'.  There are 
>warnings about cutting into sodium valves, because it's poisonous.  I 
>would imagine a solid material, even if it was poisonous, would be pretty 
>easy to handle safely compared to a liquid or powder.

Sodium (at room temperature as it would be before you start cutting on a
valve stem) is a soft lustrous solid.  You can cut Na easily with a table
knife.  When exposed to air, it rapidly starts to corrode.  This corrosion
is quite exothermic and causes the temperature of the Na to increase.  The
higher temperature causes the rate of corrosion (oxidation) to increase
thus causing the temperature to rise even more rapidly.  It can become
quite a cycle.  The metal can ignite in a shower of molten burning sodium
metal.  Quite spectacular.

Na is also extremely reactive with water.  A small pea-sized lump placed in
water produces enough heat to melt the sodium metal as it dances around on
the water surface while it reacts.  Again, quite a demonstration.  If a
large enough piece is dropped into a bowl of water the sodium can get hot
enough to ignite the hydrogen which is produced and cause a similar
spectacular display.  Bits of molten flaming sodium sticking to the ceiling.

In either case, the by-product of the sodium/oxygen reaction or the
sodium/water reaction is a strong base called lye (NaOH).

4 Na + O2 -->  2 Na2O
Na2O + H2O -->  2 NaOH  

(H2O from atmosphere or applied during clean up or present in your skin and
eyes when the sodium hits you.)

2 Na + 2 H2O -->  H2 + 2 NaOH

Lye is nasty stuff.  Very corrosive to skin and eyes.

Sodium is not particularly poisonous, after all, ordinary table salt is
sodium chloride.  It is, however, pretty dangerous stuff to be handled by
someone who doesn't know what he's doing.  Knowlege of how to handle it
doesn't help all that much.  

I suspect you may have seen warnings of "Danger" rather than "Poisonous".
However, the latter warning might make sense because everyone understands
the word.  

It's not stuff to allow your kiddies to play with.  For that matter, it's
not stuff to allow your mechanic to play with.


___
   Bob
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