Sodium acetate trihydrate - initiation of crystallization.

  • Thread starter Russel Sprout
  • Start date
  • #1
Russel Sprout

Main Question or Discussion Point

Hi,

I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
small metal disk which is stressed and will produce a click if squeezed
correctly. Once clicked the liquid will crystallize and the heat of fusion
provides the hand warming. I've been asked by my children how it works. As
they are inquisitive children, one answer leads to another question. I've
now come to the point where I cannot supply the answer and neither, it
appears, can Google. The question is this - how does the shock wave from the
click of the metal disk initiate the crystallization? I assume the
Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
unavailable, otherwise it would be prone to spontaneous crystallization.
Does the shock wave force a few molecules into the correct alignment
somehow? Any answers would help preseve my credibility.
TIA.

Steve.
 

Answers and Replies

  • #2
Ian Parker
On 1 abr, 17:28, Russel Sprout <s...@idontthinkso.net> wrote:
> Hi,
>
> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> small metal disk which is stressed and will produce a click if squeezed
> correctly. Once clicked the liquid will crystallize and the heat of fusion
> provides the hand warming. I've been asked by my children how it works. As
> they are inquisitive children, one answer leads to another question. I've
> now come to the point where I cannot supply the answer and neither, it
> appears, can Google. The question is this - how does the shock wave from the
> click of the metal disk initiate the crystallization? I assume the
> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> unavailable, otherwise it would be prone to spontaneous crystallization.
> Does the shock wave force a few molecules into the correct alignment
> somehow? Any answers would help preseve my credibility.
> TIA.
>
> Steve.


Shock waves can be quite powerful. Certainly even a finger click is
sufficient to induce chemical changes and nucleation. There are a
number of phenomena linked to this. There is luminescence in bubbles.
This was investigated extensively in a television program. When a
bubble collapses the gas can reach a high temperature. Not high enough
for thermonuclear reactions to be sure, but high enough to glow.

The Physics is basically this. Let us take a whip which is tapered
towards one end. A modest jolt will send a wave down it. Because of
tapering this wave gets amplified and the crack heard is sonic boom.
Bubbles do exactly the same thing. your finger generates enormous
force for a short instant of time. This leads to a shock wave which is
powerful enough to initiate nucleation. A few microseconds will
suffice.


- Ian Parker
 
  • #3
Uncle Al
Russel Sprout wrote:
>
> Hi,
>
> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> small metal disk which is stressed and will produce a click if squeezed
> correctly. Once clicked the liquid will crystallize and the heat of fusion
> provides the hand warming. I've been asked by my children how it works. As
> they are inquisitive children, one answer leads to another question. I've
> now come to the point where I cannot supply the answer and neither, it
> appears, can Google. The question is this - how does the shock wave from the
> click of the metal disk initiate the crystallization? I assume the
> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> unavailable, otherwise it would be prone to spontaneous crystallization.
> Does the shock wave force a few molecules into the correct alignment
> somehow? Any answers would help preseve my credibility.
> TIA.


Stuff like, "Clicking the disk forces a few molecules to change to a
solid state, and the rest of the liquid then rushes to solidify as
well."

They don't know either. Does the gizmo have an appended patent
number?

http://www.uspto.gov/patft/index.html

<http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html> [Broken]
technical ramblings

http://www.hot-pad.com/products.php [Broken]

DO NOT microwave these things.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
 
Last edited by a moderator:
  • #4
Murray Arnow
Russel Sprout <s@idontthinkso.net> wrote:
>Hi,
>
> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
>small metal disk which is stressed and will produce a click if squeezed
>correctly. Once clicked the liquid will crystallize and the heat of fusion
>provides the hand warming. I've been asked by my children how it works. As
>they are inquisitive children, one answer leads to another question. I've
>now come to the point where I cannot supply the answer and neither, it
>appears, can Google. The question is this - how does the shock wave from the
>click of the metal disk initiate the crystallization? I assume the
>Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
>unavailable, otherwise it would be prone to spontaneous crystallization.
>Does the shock wave force a few molecules into the correct alignment
>somehow? Any answers would help preseve my credibility.
>TIA.
>
>Steve.


My quick search revealed a quickie explanation at:

http://en.wikipedia.org/wiki/Sodium_acetate#_note-0 ,
or
http://tinyurl.com/2harqz ,

with a reference to another interesting page at:

www.atmos.washington.edu/2003Q3/101/demonstrations/fake_latentheat_supersaturation.html
or
http://tinyurl.com/2ddcxs

This site refers to more pages:

www.howstuffworks.com/question290.htm

and a demo at

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/ACETATE/PAGE1.HTM
or
http://tinyurl.com/2b88x7

According to the above references, you are on the right track. Your
credibility hasn't been tarnished.
 
  • #5
Ian Parker
On 1 abr, 17:28, Russel Sprout <s...@idontthinkso.net> wrote:
> Hi,
>
> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> small metal disk which is stressed and will produce a click if squeezed
> correctly. Once clicked the liquid will crystallize and the heat of fusion
> provides the hand warming. I've been asked by my children how it works. As
> they are inquisitive children, one answer leads to another question. I've
> now come to the point where I cannot supply the answer and neither, it
> appears, can Google. The question is this - how does the shock wave from the
> click of the metal disk initiate the crystallization? I assume the
> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> unavailable, otherwise it would be prone to spontaneous crystallization.
> Does the shock wave force a few molecules into the correct alignment
> somehow? Any answers would help preseve my credibility.
> TIA.
>
> Steve.


There is just one thing further you can tell your kids. Supernovae and
star formation. The shock wave of a supernova triggers star formation.
The Sun was formed shortly after a supernova explosion. We know this
because the oldest meterorites have tracks associated with Pu(244)
half life 80 million years in them. This is quite an astonishing
result. Plutonium does indeed form in rocks.

BTW - Centrifuges to me show lack of faith! An Islamic country should
look for a Plutonium mine!

- Ian Parker
 
  • #6
Dirk Bruere at NeoPax
Uncle Al wrote:
> Russel Sprout wrote:
>> Hi,
>>
>> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
>> small metal disk which is stressed and will produce a click if squeezed
>> correctly. Once clicked the liquid will crystallize and the heat of fusion
>> provides the hand warming. I've been asked by my children how it works. As
>> they are inquisitive children, one answer leads to another question. I've
>> now come to the point where I cannot supply the answer and neither, it
>> appears, can Google. The question is this - how does the shock wave from the
>> click of the metal disk initiate the crystallization? I assume the
>> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
>> unavailable, otherwise it would be prone to spontaneous crystallization.
>> Does the shock wave force a few molecules into the correct alignment
>> somehow? Any answers would help preseve my credibility.
>> TIA.

>
> Stuff like, "Clicking the disk forces a few molecules to change to a
> solid state, and the rest of the liquid then rushes to solidify as
> well."
>
> They don't know either. Does the gizmo have an appended patent
> number?
>
> http://www.uspto.gov/patft/index.html
>
> <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html> [Broken]
> technical ramblings
>
> http://www.hot-pad.com/products.php [Broken]
>
> DO NOT microwave these things.


Which is, of course, engineering speak for "stick it in the uwave and
see what happens". I assume some scientist here can supply the theory as
to why it *might* be a bad idea. Or at least, an interesting one.
Something to do with superheated liquids etc?

--
Dirk

http://www.onetribe.me.uk [Broken] - The UK's only occult talk show
Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
http://www.resonancefm.com
 
Last edited by a moderator:
  • #7
Uncle Al
Dirk Bruere at NeoPax wrote:
>
> Uncle Al wrote:
> > Russel Sprout wrote:
> >> Hi,
> >>
> >> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> >> small metal disk which is stressed and will produce a click if squeezed
> >> correctly. Once clicked the liquid will crystallize and the heat of fusion
> >> provides the hand warming. I've been asked by my children how it works. As
> >> they are inquisitive children, one answer leads to another question. I've
> >> now come to the point where I cannot supply the answer and neither, it
> >> appears, can Google. The question is this - how does the shock wave from the
> >> click of the metal disk initiate the crystallization? I assume the
> >> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> >> unavailable, otherwise it would be prone to spontaneous crystallization.
> >> Does the shock wave force a few molecules into the correct alignment
> >> somehow? Any answers would help preseve my credibility.
> >> TIA.

> >
> > Stuff like, "Clicking the disk forces a few molecules to change to a
> > solid state, and the rest of the liquid then rushes to solidify as
> > well."
> >
> > They don't know either. Does the gizmo have an appended patent
> > number?
> >
> > http://www.uspto.gov/patft/index.html
> >
> > <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html> [Broken]
> > technical ramblings
> >
> > http://www.hot-pad.com/products.php [Broken]
> >
> > DO NOT microwave these things.

>
> Which is, of course, engineering speak for "stick it in the uwave and
> see what happens". I assume some scientist here can supply the theory as
> to why it *might* be a bad idea. Or at least, an interesting one.
> Something to do with superheated liquids etc?



The clicker is a small metal disk. On does NOT microwave extended
metal objects. Put a CD in your micrwoave and give it 3 seconds.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
 
Last edited by a moderator:
  • #8
chemisttree
Science Advisor
Homework Helper
Gold Member
3,293
300
Actually you can microwave metal objects in the microwave oven without much fuss. Metal foils are a different story!

Remember, the interior of the microwave oven is entirely made of metal. Try it for yourself and see. Microwave a cup of coffee with a metal spoon. Nothing happens except the spoon gets a little warmer than the coffee. Metal foils will have some photoelectric effects and sparking can occur.

The clicker in the handwarmer will get pretty hot but so will the supersaturated solution of sodium acetate. The salt solution is almost as effective a microwave absorber as is metal!

In supersaturated solutions, the chemical potential of the solution is much higher than it is at equilibrium. The clicker produces pressure waves that send the chemical potential soaring at the interface of the clicker and the sodium acetate solution. This overpotential at the surface of the clicker is all that is needed to force the supersaturated solution to crystallize.
 
  • #9
Dirk Bruere at NeoPax
Uncle Al wrote:
> Dirk Bruere at NeoPax wrote:
>> Uncle Al wrote:
>>> Russel Sprout wrote:
>>>> Hi,
>>>>
>>>> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
>>>> small metal disk which is stressed and will produce a click if squeezed
>>>> correctly. Once clicked the liquid will crystallize and the heat of fusion
>>>> provides the hand warming. I've been asked by my children how it works. As
>>>> they are inquisitive children, one answer leads to another question. I've
>>>> now come to the point where I cannot supply the answer and neither, it
>>>> appears, can Google. The question is this - how does the shock wave from the
>>>> click of the metal disk initiate the crystallization? I assume the
>>>> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
>>>> unavailable, otherwise it would be prone to spontaneous crystallization.
>>>> Does the shock wave force a few molecules into the correct alignment
>>>> somehow? Any answers would help preseve my credibility.
>>>> TIA.
>>> Stuff like, "Clicking the disk forces a few molecules to change to a
>>> solid state, and the rest of the liquid then rushes to solidify as
>>> well."
>>>
>>> They don't know either. Does the gizmo have an appended patent
>>> number?
>>>
>>> http://www.uspto.gov/patft/index.html
>>>
>>> <http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/thermal/th4c/patentheatpack.html> [Broken]
>>> technical ramblings
>>>
>>> http://www.hot-pad.com/products.php [Broken]
>>>
>>> DO NOT microwave these things.

>> Which is, of course, engineering speak for "stick it in the uwave and
>> see what happens". I assume some scientist here can supply the theory as
>> to why it *might* be a bad idea. Or at least, an interesting one.
>> Something to do with superheated liquids etc?

>
>
> The clicker is a small metal disk. On does NOT microwave extended
> metal objects. Put a CD in your micrwoave and give it 3 seconds.


Ah... thought you were referring to supersatured Na acetate rather than
a piece of metal. Although I have to say that I found the CD in the
microwave to be quite impressive.

Ditto eggs. And to keep on topic, does anyone have any idea of the
internal pressure needed to rupture an egg?

--
Dirk

http://www.onetribe.me.uk [Broken] - The UK's only occult talk show
Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
http://www.resonancefm.com
 
Last edited by a moderator:
  • #10
Russel Sprout
"Russel Sprout" <s@idontthinkso.net> wrote in message
news:57a0moF2berukU1@mid.individual.net...
> Hi,
>
> I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> small metal disk which is stressed and will produce a click if squeezed
> correctly. Once clicked the liquid will crystallize and the heat of fusion
> provides the hand warming. I've been asked by my children how it works. As
> they are inquisitive children, one answer leads to another question. I've
> now come to the point where I cannot supply the answer and neither, it
> appears, can Google. The question is this - how does the shock wave from
> the
> click of the metal disk initiate the crystallization? I assume the
> Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> unavailable, otherwise it would be prone to spontaneous crystallization.
> Does the shock wave force a few molecules into the correct alignment
> somehow? Any answers would help preseve my credibility.
> TIA.
>

Thanks all,

So that's it, the shock wave aligns a few molecules in close enough
proximity to start the process of crystallization, probably. Somehow, I'd
been hoping for something a little more exotic. The irony is, that the pack
was going to be used during a fairly high altitude outing (my wife gets cold
hands easily), as it turned out it was calm and sunny and on the S facing
scree slope, a cooling pack would have ben a better idea.

Thanks again,
Steve.
 
  • #11
Uncle Al
Russel Sprout wrote:
>
> "Russel Sprout" <s@idontthinkso.net> wrote in message
> news:57a0moF2berukU1@mid.individual.net...
> > Hi,
> >
> > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> > small metal disk which is stressed and will produce a click if squeezed
> > correctly. Once clicked the liquid will crystallize and the heat of fusion
> > provides the hand warming. I've been asked by my children how it works. As
> > they are inquisitive children, one answer leads to another question. I've
> > now come to the point where I cannot supply the answer and neither, it
> > appears, can Google. The question is this - how does the shock wave from
> > the
> > click of the metal disk initiate the crystallization? I assume the
> > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> > unavailable, otherwise it would be prone to spontaneous crystallization.
> > Does the shock wave force a few molecules into the correct alignment
> > somehow? Any answers would help preseve my credibility.
> > TIA.
> >

> Thanks all,
>
> So that's it, the shock wave aligns a few molecules in close enough
> proximity to start the process of crystallization, probably. Somehow, I'd
> been hoping for something a little more exotic. The irony is, that the pack
> was going to be used during a fairly high altitude outing (my wife gets cold
> hands easily), as it turned out it was calm and sunny and on the S facing
> scree slope, a cooling pack would have ben a better idea.


They are available - two-chambered plastic pouches, water and either
ammonium nitrate or urea. Mix and you have a cold pack. It doesn't
reverse for reuse.

Hot bandages are iron filings, activated charcoal, salt, water, and
sawdust sealed in an oxygen barrier bag. When you breach containment
the iron oxidizes over a few hours and the reaction provides sustained
warmth. The same chemistry is used in oxygen-scrubbing sachets, in
the manner of silica gel desiccant packs for water, for air-sensitve
bottles of pharamceuticals and the like. We all know about oily rags
(especially linseed oil in a wood or print shop) reacting with air,
warming, and igniting.

If you were Al Gore green you would have sheets of solar cells on your
back and hat to sustainable-resource non-polluting solar power your
reusable electrical warmers (presumably not fabricated in countries
overflowing with objects of tolerence). You would then learn why
engineers respect thermodynamics when designing capital equipment
installations. Only the math is consequential.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
 
  • #12
Uncle Al
Russel Sprout wrote:
>
> "Russel Sprout" <s@idontthinkso.net> wrote in message
> news:57a0moF2berukU1@mid.individual.net...
> > Hi,
> >
> > I have a hand warmer a plastic packet filled with Na(C2H3O2)-3H2O and a
> > small metal disk which is stressed and will produce a click if squeezed
> > correctly. Once clicked the liquid will crystallize and the heat of fusion
> > provides the hand warming. I've been asked by my children how it works. As
> > they are inquisitive children, one answer leads to another question. I've
> > now come to the point where I cannot supply the answer and neither, it
> > appears, can Google. The question is this - how does the shock wave from
> > the
> > click of the metal disk initiate the crystallization? I assume the
> > Na(C2H3O2)-3H2O is pretty pure and physical nucleation sites are
> > unavailable, otherwise it would be prone to spontaneous crystallization.
> > Does the shock wave force a few molecules into the correct alignment
> > somehow? Any answers would help preseve my credibility.
> > TIA.
> >

> Thanks all,
>
> So that's it, the shock wave aligns a few molecules in close enough
> proximity to start the process of crystallization, probably. Somehow, I'd
> been hoping for something a little more exotic. The irony is, that the pack
> was going to be used during a fairly high altitude outing (my wife gets cold
> hands easily), as it turned out it was calm and sunny and on the S facing
> scree slope, a cooling pack would have ben a better idea.


They are available - two-chambered plastic pouches, water and either
ammonium nitrate or urea. Mix and you have a cold pack. It doesn't
reverse for reuse.

Hot bandages are iron filings, activated charcoal, salt, water, and
sawdust sealed in an oxygen barrier bag. When you breach containment
the iron oxidizes over a few hours and the reaction provides sustained
warmth. The same chemistry is used in oxygen-scrubbing sachets, in
the manner of silica gel desiccant packs for water, for air-sensitve
bottles of pharamceuticals and the like. We all know about oily rags
(especially linseed oil in a wood or print shop) reacting with air,
warming, and igniting.

If you were Al Gore green you would have sheets of solar cells on your
back and hat to sustainable-resource non-polluting solar power your
reusable electrical warmers (presumably not fabricated in countries
overflowing with objects of tolerence). You would then learn why
engineers respect thermodynamics when designing capital equipment
installations. Only the math is consequential.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
 
  • #13
1
0
So that's it, the shock wave aligns a few molecules in close enough
proximity to start the process of crystallization, probably. Somehow, I'd
been hoping for something a little more exotic. The irony is, that the pack
was going to be used during a fairly high altitude outing (my wife gets cold
hands easily), as it turned out it was calm and sunny and on the S facing
scree slope, a cooling pack would have ben a better idea.


Um, is it really a shock wave effect or just generation of nucleation sites to catalyse crystallisation.

I had though that it was like getting a supercooled bottle of beer etc, where minimal movement can cause (sadly) complete crystallisation.

I dont know if the metal disc would harbour any salt crystals in surface imperfections or perhaps metal fragments act as nuclei??
 

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