On Tue, 14 Jun 2005 10:11:03 -0800, (Floyd L.
Davidson) wrote:

John Fields wrote:
On Tue, 14 Jun 2005 08:32:09 -0800, (Floyd L.
Davidson) wrote:

Dr. Polemic wrote:
On Tue, 14 Jun 2005 01:14:42 -0800, (Floyd L. Davidson) wrote:

Dr. Polemic wrote:
Danged, several weeks of work shot because it just hadn't
occurred to him that ni-cad would boil at room temperature.

I doubt that it *boils* at room temperature; evaporates slowly, maybe. At least, not at
the temperature of any rooms I've been in.

Oh, it boiled off!

So, tell me, what is the vapor pressure of Cadmium at 20 degrees C?

I don't know. Look it up.

Takes a nice little vaccuum pump to do it though.

---
Yer fulla ****.

Well John, it probably was cadmium plating, not ni-cad. And I'm
not sure what the actual temperature was, though it certainly
wasn't much above room temperature (the experiment failed before
it was exposed to significant nuclear radiation, which would
have provided heat).

---
So now we don't even know whether it was cadmium or not, we also don't
know what the temperature or the pressure was in the chamber, _and_
we learn that the sample was being subjected to ionizing radiation!

What next?
---

However, the metal plating on the hardware boiled!

Uh-huh... sure it did.
---

Here's a chart you might want to look at. Note the relative
vapor pressure of cadmium compared to other metals. Then think
about "a nice little vacuum pump".

http://www.veeco.com/learning/learni...orelements.asp

My point, since it went right over your head when stated as a
puzzle, is that temperature alone is not what defines when
something "boils", and some materials that you wouldn't normally
think of in terms of a vapor can in fact "boil". "Out-gas"
might be a better term.

---
Blah, blah, blah, ****ing blah.
More posturing, platitudes and crapola.

'Outgassing' is an entirely different phenomenon which manifests
itself as the extraction of gas entrained in a material by and into a
vacuum surrounding the gassy material. A good example is the frothing
that occurs when a two-part epoxy is mixed and then placed in a
vacuum. After the release of the gas and the collapse of the froth,
it would still be possible for the epoxy to boil in the vacuum if the
vacuum were hard enough and the temperature high enough, but that
would then be true boiling and _not_ outgassing.

Just so you won't have to extrapolate to 20°C from those charts of
yours, here's Dr. Polemic's data:

"The CRC handbook indicates that the vapor pressure of cadmium is
about 10^-12 torr at room temperature (20 degrees). This is better
than the vacuum at the moon. The best vacuum pumps available today
can't hit that in a bell jar, much less 40 years ago."

--
John Fields
Professional Circuit Designer