On 28 Jan, 19:41, alchazz <no.s...[at]wanted.com> wrote:

- quote -

Sorry to labor the point Al, but I found my other favorite reference
for gallium amalgams (i.e. where the liquid metal used to formulate
the amalgam is gallium and not mercury - so there's no mercury in
'em).

This is from the Institute of Physics document service website at:

http://www.priorartdatabase.com/IPCOM/000137544/

"Hermetic Sealing of Electronic Hardware Using Gallium Amalgams

In this proposed invention, the gallium amalgam is mixed in a ball
mill, but the mixing action is minimized to limit the abrasion of the
metal particles so as not to have the liquid gallium wet the metal
particles. Since the metal particles are not wetted by the liquid
gallium, they will not dissolve in the liquid gallium. The pot life is
thus much extended. The liquid gallium, laden with metal particles, is
placed on the surfaces to be joined. The faying surfaces are pressed
together and then vibrated with respect to each other. The compressive
stresses and relative motion between the surfaces cause the metal
particles to abrade against each other and the faying surfaces. The
particles and the faying surfaces become clean and thus wettable by
the liquid gallium. The amalgamation process begins solidifying the
amalgam and joining the two surfaces. When the amalgamation process is
complete, the amalgam becomes solid and holds the faying surfaces
together.

The amalgam can be a ternary alloy having 5-35% Cu and 15-30% Ni in
liquid gallium. The nickel and copper particle size has to be less
than about 0.05 mm so that the faying surfaces are not kept
excessively apart by the particles. The relative motion between the
faying surfaces to initiate the amalgamation action can be achieved
by..."

So you see there really are amalgams with no mercury in them - but it
is still correct to call them amalgams because of the nature of the
process by which they are formed.

But like I said, yours is a common misconception, so there's no need
to feel stupid.

On the other hand, if you begin to wonder whether the idea that
"there's nothing wrong metal amalgam dental fillings" might also be a
common misconception let me know and I'll give you some pointers on
how you might find out.

Keith P Walsh

Keith P Walsh wrote, On 1/31/2009 3:30 AM:
- quote -

thermoelectric effect across an thermal gradient in an amalgam. Do the
experiment and find out for yourself.

--

Paul D Oosterhout
I work for SAIC (but I don't speak for SAIC)

On 28 Jan, 19:41, alchazz <no.s...[at]wanted.com> wrote:

- quote -

That's a common misconception.

That "an amalgam" has come to imply mercury, particularly in the
dental profession, is because mercury amalgams are the most common.

But mercury amalgams are NOT the only type of amalgam, as you can see
by extracts from the book, "Principles of Soldering", by Giles
Humpston and David M Jacobson, published by ASM International (April
2004) and endorsed by The Materials Information Society.

The parts which are of interest to us are:

Page 115 - Section 5.4.1 - Amalgams Based on Mercury

Page 116 - Section 5.4.2 - Amalgams Based on Gallium

"Gallium melts at 29 deg C and is therefore a potential base for
formulating very low-process-temperature amalgams without the toxic
hazard associated with mercury"

(Note, there's no mercury in these amalgams.)

Page 117 - Section 5.4.3 - Amalgams Based on Indium

"Indium is another liquid metal that can be considered as a base for
amalgam systems. "

(There's no mercury in these amalgams either.)

You can find details of this book at:

http://books.google.com/books?id=cQ6...OWq3Uw#PPP1,M1

When I first quoted these pages (see message in thread "Lessons on
Alloys, Amalgams, and Pleonasms (2)" of 1 September 2007)
they were available for reading at the above URL.

Unfortunately it looks like since then they've been made unavailable!
(I tell ya, if I were a conspiracy theorist ... ).

Anyway the quotes are genuine.

So come on Al. Please don't simply ignore this post just because
you've been proved wrong.

Get typing and give us your opinion now (and don't be shy about cross-
posting to the other groups).

Keith P Walsh

On 30 Jan, 16:27, Paul O <first.d.l...[at]company.com> wrote:

- quote -

I'll bear it in mind.

In the meantime can I take it that you agree with my description of
the difference between an alloy and an amalgam?

Keith P Walsh

Keith P Walsh wrote, On 1/30/2009 3:41 AM:
- quote -

Why would you trust the results from any experiments carried out by the
ADA, the BDA, or the FDA? Do the experiment yourself and then you will
know for sure whether your hypothesis is correct.

If your experiment has any sort of positive result, then other
researchers will be come interested in the phenomenon and begin their
own investigations. Then the ADA and the BDA will be forced to take notice!

You could be a hero! All you have to do is a little work.

Best of luck
Paul O.

--

Paul D Oosterhout
I work for SAIC (but I don't speak for SAIC)

On 28 Jan, 17:46, Paul O <first.d.l...[at]company.com> wrote:
- quote -


I am proposing the hypothesis that the degree of electromagnetic
disturbance caused by the application of a temperature gradient to an
amalgam should be greater than that caused by the application of a
temperature gradient to either a pure metal or a true alloy.

The justification for this proposal is based on the fact that an
amalgam has a much greater degree of material inhomogeneity than
either a pure metal or an alloy, and it should therefore be expected
to generate internal thermoelectric eddy currents to a much greater
extent when subjected to thermal gradients.

Now, Professor Wang of the University of Akron has asserted that the
relevant "coupling parameter", which gives an indication of the size
of the electromagnetic disturbance generated by a material with
respect to the size of any temperature differential applied to it,
would be too low in "most metals" to suggest that any local
electromagnetic effect produced could have an influence on
neurological tissue in the direct vicinity of the material.

However, as I have shown (and I note that in your own contribution you
have not registered any disagreement with this point) amalgams
(including dental amalgams) are different from "most metals" in the
crucial respect that they have a much greater degree of material
inhomogeneity.

So, the question is, how can we be sure that amalgams (and most
importantly dental amalgams) come within the "safe" range defined by
Professor Wang with regard to electromagnetic activity?

Well there's only one scientific way to do that and that is to carry
out experimental investigations to see if the electromagnetic
disturbances generated by amalgams as a result of their thermoelectric
behavior can be measured.

And if they can be measured then it would also be necessary to carry
out further experimental investigations to determine whether or not
the measured disturbances are able to influence the function of any
neurological tissue nearby.

According to the established principles of scientific understanding,
without any of the experimental investigations here described having
been carried out, it is not possible for any of us (including
Professor Wang) to conclude whether or not the natural electromagnetic
behavior of an amalgam dental filling is capable of dissipating
electrical energy through the nerves in people's heads.

And it is therefore not possile to declare amalgam fillings "safe" in
this respect.

I do not advocate the use of metal amalgams in restorative dentistry.

Professional bodies such as the American Dental Association, the
British Dental Association, the US FDA, etc., they do that. And
therefore the responsibility for carrying out the experimental
procedures to demonstrate whether or not such materials are "safe" for
this purpose lies with them, not with me.

Now I appreciate that you have succeeded in convincing yourself that
this responsibility does lie with me.

But you are wrong, it doesn't.

Keith P Walsh

In sci.physics Paul O <first.d.last[at]company.com> wrote:
- quote -

Hell, a couple of years ago I found what he needed on e-bay for well
under $100 and offered to buy it for him if he made and published
the measurements.


--
Jim Pennino

Remove .spam.sux to reply.

Keith P Walsh wrote, On 1/28/2009 4:34 AM:
- quote -

Yes, I can think of an experimental procedure. Several people on these
newsgroups (myself included) have described to you exactly how to
measure the thermoelectric properties of metal amalgam dental fillings.
But it has been a complete waste of time. In the last 15+ years that
I've been reading your posts, you have never once made even the
slightest effort to test your hypothesis.

Look, this is not that difficult. I will help you if you are willing
purchase some materials, borrow or rent a good digital volt meter,
construct a test apparatus, and then run your experiment. Otherwise,
feel free to continue shouting in the wilderness.

--

Paul D Oosterhout
I work for SAIC (but I don't speak for SAIC)

The following statement was made by Professor Xu Wang of the
University of Akron in response to a question regarding the
relationship between the thermoelectric properties and the
electromagnetic behavior of metal amalgam dental fillings.

"Theoretically electromagnetic field will be generated by thermal
gradient. But the thermoelectric coupling parameter in most metals is
very low (0.001-0.01). So I don't think the induced electromagnetic
field is significant enough to influence the neurological tissue
nearby."

Amalgams, including dental amalgams, are not like most other metals in
at least one crucial respect; they have a much greater degree of
material inhomogeneity.

This is true when compared either with pure metals, such as copper,
silver, etc., or with true alloys such as brass.

The explanation for the difference in the material homogeneities of
amalgams and true alloys lies in the difference between the methods by
which the two types of material are formed.

When a true alloy is formed, the component metals are mixed together
at a temperature which is greater than the melting point of all of
them. Then, after having been mixed thoroughly in its fully liquid
state, the mixture is allowed to solidify by cooling at a controlled
rate.

By contrast, in an amalgamation process, bits of solid metal, which
may themselves be of either pure metal or an alloy, are mixed together
with a liquid metal at a temperature which is BELOW THE MELTING POINT
of the solid component(s). (And in the case of dental amalgam, where
mercury is used as the liquid metal amalgamating agent, this process
is normally performed at room temperature.)

In the setting process of such an amalgam, the liquid mercury becomes
part of the solid material not as a result of any subsequent reduction
in temperature, but by joining in solid solution with the outer layer
of the solid particles of metal with which it was mixed. But of
course, not all of the volume of the solid particles is involved in
this process and, as a result, the microstructure of the resulting
solid amalgam is as depicted in the schematic diagram at:

http://book.boot.users.btopenworld.com/setting.htm

In this diagram the lumps of "unreacted alloy" (denoted "gamma") are
the cores of the original grains of solid silver-tin alloy which have
not mixed with any of the mercury during the amalgamation process.

At this scale it is not possible to show the spatial relationship
between the atoms of silver and the atoms of tin in these alloy
"cores". The alloy has too great a degree of homogeneity for this to
be done.

However, the relative inhomogeneity of the "amalgam" is clearly
depicted by the sizes of the unreacted alloy cores. (These being held
together by a solid matrix of a dissimilar mixture of metals (denoted
"gamma-1") which does have mercury in it, and which may be presumed
therefore to have dissimilar physical properies.)

Now, I have it on good authority from Professor David B Mahler of The
Oregon Health & Science University School of Dentistry that the median
size of the "unreacted" grains of original solid alloy in dental
amalgams is in the order of 30 microns. Scientists with experience of
electrical phenomena at the nano scale might provide some testimony to
the significance of this figure.

The question which remains unanswered is this; whilst it may be
appropriate to quote a "coupling parameter" for the local
electromagnetic effect arising purely from temperature difference in a
homogeneous metallic material, such as a pure metal or an alloy of
metals (for example the type of alloy which may be mixed with liquid
mercury to form an amalgam), is it not the case that the dominant (and
potentially much larger) electromagnetic effect arising as a result of
temperature differences in a more inhomogeneous mixture of dissimilar
metals, such as an amalgam, is more likely to be that caused by the
establishment of thermoelectric eddy currents which would be necessary
for maintaining physical equilibrium against temperature gradient in
such an inhomogeneous medium?

Can anyone think of any experimental procedure which might be employed
in order to demonstrate the case either way?

And is it possible that Professor Wang was failing to take into
account the degree of inhomogeneity of metal amalgams, which is much
greater than "most metals", when estimating the size of the
electromegnetic disturbance produced by thermoelectric effects in
dental amalgams?

Professor Wang's home page is at:

http://www.ecgf.uakron.edu/~pan/wang/

Keith Walsh

PS, Any dentists out there who don't know anything about the
thermoelectric behavior of dental amalgams can always quote professor
Wang's "coupling parameter" statement if pressed. But I would strongly
advise you to make sure that he knows what he's talking about first.