Working with mercury

[Bob E.]

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.

[Salmon Egg]

In article

Post by Bob E.
<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?
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.

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.

[Bob E.]

Post by Salmon Egg
If PVC is not elastic enough, there are many other plastics that may be.
Polyester (Lexan) will stretch a lot before failing completely.
[Sam]

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.

[Bob E.]

Post by Bob E.
Mercury: 182
PVC: 156
Polycarbonate (Lexan): 195-210

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.

[Salmon Egg]

In article

Post by Bob E.

Post by Bob E.
Mercury: 182
PVC: 156
Polycarbonate (Lexan): 195-210

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.

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.

[Bob E.]

Post by Salmon Egg
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.

...

Post by Salmon Egg
You should get something like dV = 3 * alpha * V * dT.

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.

Post by Salmon Egg
If not, you should not be doing the experiment in the first place.

I'll decide that, thank you.

[dlzc]

Dear Bob E.:

On Monday, December 3, 2012 2:25:18 PM UTC-7, Bob E. wrote:
...

Post by Bob E.
This does not accurately calculate the change of
the interior of a cylinder made of the material.
The cylinder will expand lengthwise,

Correct.

Post by Bob E.
but the walls of the cylinder thicken,

Incorrect.

Post by Bob E.
expanding outward

Correct.

Post by Bob E.
*and* inward.

Incorrect.

Post by Bob E.
Such a calculation (above) doesn't take into
account the latter expansion.

Because it does not exist. Heating a hoop, allows the hoop to slip over something it would not fit before. The circumference is much larger than the wall thickness, and heating expands the circumference too.

David A. Smith

[Bob E.]

Post by dlzc
Because it does not exist. Heating a hoop, allows the hoop to slip over
something it would not fit before. The circumference is much larger than the
wall thickness, and heating expands the circumference too.
David A. Smith

Ah, the jr. high school thermal expansion experiment comes back to me: brass
ball & loop.

Thanks!

[Syd Rumpo]

On 03/12/2012 21:25, Bob E. wrote:

<snip>

Post by Bob E.
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.

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

[Mark Thorson]

Post by Syd Rumpo
<snip>

Post by Bob E.
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.

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.

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.

[Bob E.]

Post by Mark Thorson
The change in volume is the cube
of the change in linear dimension.

Thanks for the confirmation, Mark.

Happy holidays.

[m***@gmail.com]

Post by Bob E.

Post by Mark Thorson
The change in volume is the cube
of the change in linear dimension.

Thanks for the confirmation, Mark.
Happy holidays.

So... how did the experiment go?

:-)

Michael

[Charles]

Post by Bob E.
<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?

Leave an air bubble.

Ch

[Bob E.]

Post by Charles
Leave an air bubble.
Ch

Yes, of course.

Thanks.

[Father Haskell]

<http://www.sciencecompany.com/Mercury-Metal-quicksilver-3X-Distilled-...
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?
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.

Containment bucket?