RE: Mercury - topic drift

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: William Beaty <billb@xxxxxxxxxx>

On Fri, 10 Mar 2006, Tesla list wrote:

> Actually, what you are probably seeing is water vapor and not Mercury.

In other words, you're assuming that the group who made the video is
lying.  What makes you leap to such a conclusion?   Seriously, I'd like to
know.  Their demo looks straightforward to me.

Try it yourself.  This "mercury plume" trick is a fairly well-known
physics demo. You need a shortwave quartz UV lamp (EPROM eraser,) a
filter to pass that one Hg emission line, and a piece of paper as the
fluorescent screen (most paper will fluoresce bright blue under short UV.)

Someone performed it at one of our local "weird science" meetings a few
years ago.  It's teriffically sensitive.  For example, if you touch liquid
mercury with a fingertip, then perform the UV shadow experiment an hour
later, you can see the shadow of a vapor plume coming from that fingertip
and not from others.  It's quite impressive.

The only hard-to-get part was the UV filter.  I think he said he bought it
from a geologist supply catalog.  The filter is definitely required; I
tried the same test with just an EPROM eraser and fluorescent screen, and
couldn't see any dark plume from liquid mercury.  The visible light from
the UV tube washes out everything.

Now I'm getting curious.  I'll see if I can track down that filter.
Right now I happen to have a loose crown, a "removable tooth" with plenty
of amalgam parts.  (BTW, my cracked crown has started having a metallic
flavor, so perhaps mercury escapes because bacterial acid dissolves the
metal.)


> A properly made amalgam has no "free" Mercury.

But experiment beats theory.

*If* any typical dental filling can make a vapor shadow when warmed up and
illuminated with UV, *then* fillings do outgas measurable mercury vapor.

> Another amalgam in common
> use is Concrete.  One of the ingredients (slaked Lime) is horribly
> caustic and will cause skin damage if not washed off completely.
> People are using Concrete for kitchen countertops and eating off it.
> Kids play on it outside.  You simply do not hear about skin irritation
> with concrete.

That's not an honest example.  For a proper analogy, calcium would have to
be a toxic heavy metal, and in that case we wouldn't care about skin
irritation, instead we'd check to see if incredibly tiny amounts of
calcium were escaping from wet sidewalks and building up in the organs of
kids playing outdoors.  (Or in a similar vein, note that the mercury from
fillings is far too small to directly cause problems. Instead it has to
build up in tissues over time.)

> Concrete contains a toxic component but a properly made
> amalgam will bind all ingredients together permanently.

Perhaps your statement only applies to materials such as calcium having
low vapor pressures?


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William J. Beaty                            SCIENCE HOBBYIST website
billb at amasci com                         http://amasci.com
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