RE: What's the sodium for?

[Robert Myers <rmyers@inetone.net>]

>The reason there was a "danger" warning is because Sodium is EXTREMELY
>dangerous, even in small quantities.  You wouldn't have time to ingest, or
>even touch it to get poisoned by it.

I beg your pardon, Brett.  But to use "Poison" is an error.  Sodium oxide
or sodium hydroxide are hazardous due to the presence of the hydroxide ion.
 The fact that it is associated with a sodium ion is irrelevant.  Potassium
hydroxide is as hazardous as sodium hydroxide.  Sodium chloride is ordinary
table salt and, blood pressure concerns aside, is not poisonous.  Therefore
sodium is not poisonous.  Neither is potassium as in potassium chloride
("lite salt" used by people on a low sodium diet).

The discussion was about the term "poisonous" vs. the term "Dangerous".
Metallic sodium is _indeed_ dangerous.  It is not poisonous.  Sodium
hydroxide, formed by the reaction of sodium with water is also quite
hazardous but I'm not sure if even that would be classified as a poison.
It is a caustic.  It will "burn" tissues by hydrolysing fats, oils, and
proteins - nasty stuff for a layman to handle.  But a poison?  I guess it
depends on your definition of poison.

>It reacts in a very violent way to any form of moisture, and if it comes in
>direct contact with water, large amounts of hydrogen are released.
>Hydrogen can then explode.

It takes a pretty decent amount of sodium to get to this stage but you are
correct.  The hydrogen produced can explode.  This is usually a small scale
explosion which is not one of those wall cracking window shattering types
so favored by some of our more militant citizens.  However, such an
explosion has the capability of hurling burning molten sodium for distances
of several feet.  This in itself is a significant hazard.

>Phosphorus is even worse...both have to be stored under oil to avoid
>contact with moisture.

Wrong.  Sodium is stored under kerosene to exclude air.  It is also stored
and shipped inside vacuum sealed cans, like a tennis ball cans, without the
kerosene.  Once the can is opened and a small amount of sodium used for
some purpose, the remainder of the sodium must then be stored under kerosene.

Phosphorous comes in two main allotropic flavors.  Red and white.

Red phosphorus is basically no problem.  You simply store it in a stoppered
bottle.  A screw-cap reagent bottle suffices quite nicely.  You can get it
to burn but you must actually try to burn it rather than have to try not to
let it burn.

White phosphorous, however, is a different matter.  It must be stored under
water (not oil or kerosene for the purpose of excluding air).  When removed
from the water, atmospheric oxygen starts to react with the phosphorous to
form a cloud of P4O10 fumes and a lot of heat.  (Often you see the formula
as P2O5 but it is actually P4O10.)

P4 (white phosphorous) + 5 O2 -->  P4O10  +  __heat__

It is this reaction which produces the star burst effect of a phosphorous
grenade bursting against a tank as so vividly demonstrated in lots of old
war movies.  Weapons of this type were used during WWII to bomb civilians
in Tokyo.  The only way you can put out a phosphorous fire is to submerge
it in water or perhaps sand (to exclude oxygen).  Bring it out of the water
and it will spontaneously re-ignite.  Nice way to treat people, huh?  :-( 

Oops.  Guess I'd better get down from my soapbox.  I have certain pacifist
leanings.


___
   Bob
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