On Tue, 14 Jun 2005 11:44:02 -0700, Dr. Polemic
wrote:

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).

However, the metal plating on the hardware boiled!

Here's a chart you might want to look at.

The information on this web page doesn't indicate directly what the vapor pressure of
cadmium is at 20 degrees, but extrapolating the numbers in the table gives a value of
10^-12 torr at 30 degrees. It takes more than a "nice little vacuum pump" to achieve
this. But I see that you're waffling now; you now say that "I'm not sure what the actual
temperature was". I would certainly agree that cadmium can be made to boil if the
temperature is high enough, but you claimed "room temperature". One thing is pretty
certain; you weren't "boiling" cadmium at 20 degrees because you have to get the pressure
below the vapor pressure of cadmium at 20 degrees before it "boils" and a "nice little
vacuum pump" of 40 years ago couldn't do that under a bell jar.


Note the relative
vapor pressure of cadmium compared to other metals. Then think
about "a nice little vacuum pump".

Think about why the graphs on that web page don't go below 10^-7 torr. Then think about
cadmium's (extrapolated) vapor pressure of 10^-12 torr at 30 degrees.


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

My point, since it went right over your head

Did this go over your head, John?

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.

---
Not at all. Even Betty Crocker (last time I looked) had baking
altitude adjustments on her boxes of cake mix.

--
John Fields
Professional Circuit Designer