Working with mercury

I want to explore the magnetic properties of elemental mercury:
<http://www.sciencecompany.com/Mercury-Metal-quicksilver-3X-Distilled-12lb-
P16388.aspx>
I was planning on placing it in a non-magnetic tube, maybe PVC or such, capped at both ends. But mercury's thermal expansion properties pose some containment issues. I won't be heating it, intentionally, but magnetic fields applied may cause some heating, added to ambient temp effects.
I want to find a way to safely contain mercury so as to minimize the risk of accidental release.
Quantity is 1 lb (~450 gm)
Suggestions?
USENET disclaimer: Constructive replies only please. I understand mercury's toxic risks and dangers to my health if mishandled, so please don't repeat here. If your suggestion is to terminate my plans, please don't reply.
Thanks.
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You do not say how high the temperature you want is or other practical limitations will be. There is a good chance that PVC is elastic enough to expand more than the mercury does. Moreover, my guess is that the PVC will expand sufficiently under pressure without breaking. You should be able to calculate such things.
If PVC is not elastic enough, there are many other plastics that may be. Polyester (Lexan) will stretch a lot before failing completely.
--

Sam

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The temperatures are unknown. I will not be heating -- with intent -- the mercury (this is not an induction oven design), just whatever temperature increase results from induction as a result of the experiment. This is yet to be discovered empirically.
Here's some thermal coefficient of (volumetric) expansion figures:
<https://en.wikipedia.org/wiki/Thermal_expansion#Thermal_expansion_coefficient s_for_various_materials>
Mercury: 182 PVC: 156 Polycarbonate (Lexan): 195-210
The closer the coefficient of the 2 materials the less will be the pressure (or vacuum) build-up inside the container. Pressure will be least with a container made from polycarbonate compared to other plastics for which I could find expansion specs. Then we depend on the strength of the material & adhesives used to build the container.
Thanks.
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I'm approaching this wrong. Mercury expansion coefficient is volumetric: the volume of the liquid metal increases with temperature. That's simple.
The plastic which makes up the cylinder also increases with temperature, but not the necessarily the volume within the cylinder.
How do I determine what the change in volume of the cylinder (PVC vs. polycarbonate) will be per degree (preferably celsius)?
Thanks.
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Assuming isotropic material, the volume of a cylinder, for example, is
V = pi * r^2 * L
It then is a simple calculus problem.
dV = 2 * pi r * dr + pi * r^2 * dL
dr = alpha * r * dT; dL = L = alpha * L * dT
From this you should be able to figure out dV/dT. If not, you should not be doing the experiment in the first place.
You should get something like dV = 3 * alpha * V * dT.
--

Sam

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...

Thanks for your reply.
This does not accurately calculate the change of the interior of a cylinder made of the material. The cylinder will expand lengthwise, but the walls of the cylinder thicken, expanding outward *and* inward. Such a calculation (above) doesn't take into account the latter expansion.

I'll decide that, thank you.
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On 03/12/2012 21:25, Bob E. wrote:
<snip> > This does not accurately calculate the change of the interior of a cylinder

No, the cylinder OD will increase and its ID will also increase, but not as much. Think of it as being made of (say) a cubic arrangement of atoms where the sides of the cubes (the bonds) all lengthen by the same amount when heated.
Cheers
--
Syd

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Syd Rumpo wrote:

Assuming everything is at equilibrium temperature, the proportions of the cylinder will not change. That is, the ratios of length vs. diameter, length vs. wall thickness, and diameter vs. wall thickness remain constant. The change in volume is the cube of the change in linear dimension.
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Thanks for the confirmation, Mark.
Happy holidays.
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Leave an air bubble.
Ch
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Yes, of course.
Thanks.
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elds

of

Containment bucket?
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