Magpie
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Little Hotties
Mrs Magpie brought home some Little Hotties (LittleHottiesWarmers.com) and gave one packet to me as she knew I would find it interesting.
They are used as hand warmers etc, during winter outdoor activities. They are little 2"x3" packets of some powder in a plasticized fabric pouch. I
have one in my hand right now and it is indeed warming to maybe 10C above body temperature. The listed ingredients are: "iron powder, water, salt,
activated charcoal & vermiculite."
So, anyone care to speculate on what reactions are generating this heat?
The single most important condition for a successful synthesis is good mixing - Nicodem
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The WiZard is In
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Quote: Originally posted by Magpie  | Mrs Magpie brought home some Little Hotties (LittleHottiesWarmers.com) and gave one packet to me as she knew I would find it interesting.
They are used as hand warmers etc, during winter outdoor activities. They are little 2"x3" packets of some powder in a plasticized fabric pouch. I
have one in my hand right now and it is indeed warming to maybe 10C above body temperature. The listed ingredients are: "iron powder, water, salt,
activated charcoal & vermiculite."
So, anyone care to speculate on what reactions are generating this heat? |
Lee R Summerlin
Christie L Borgford
Julie B Ealy
Chemical Demonstrations: A Source Book for Teachers
Volume 2, Second Edition
ACS 1988
ENERGY CHANGES 101
54. A Chemical Hand Warmer
Several materials are placed in a plastic baggie. When the
substances are mixed, a slow and steady evolution of heat results.
This reaction is similar to that of the commercially available hand
warmers.
Procedure
Wear safety goggles.
1. Place about 25 g of iron powder in a small plastic baggie.
2. Add 1 g sodium chloride.
3. Close the bag and shake to mix the chemicals.
4. Add about 1 Tbs of small vermiculite and mix again. The "hand
warmer" is now ready to be activated.
5. When you are ready for the demonstration, add 5 mL of water to
the bag and seal it with a metal twist tie.
6. Squeeze and shake the bag to thoroughly mix the contents.
7. After a minute or so, a noticeable amount of heat will be produced.
8. Pass the hand warmer around the class.
Reactions
1. This demonstration is essentially an oxidation reduction
reaction. Iron is oxidized in an exothermic reaction.
4Fe(s) + 302(g) ——> 2Fe2O3(s) + heat
2. The oxygen is reduced, picking up the electrons lost by the iron.
3. Sodium chloride provides electrolytes to catalyze the reaction.
4. Vermiculite helps insulate the hand warmer and contain the heat
and distribute it in the bag.
Material
Iron powder: 100 mesh works well.
Teaching Tips
NOTES
1. The heat of formation of Fe203 is 196.5 kcal/mol.
2. If you want to prepare a bag and use it later to produce heat,
squeeze out all the air after everything has been added and tie it
securely. When you want to activate the reaction, open the bag,
let in some air, and tie the bag again.
3. Vermiculite is a minera I actually the hydrous silicate of
aluminum, magnesium and iron. When it is heated, it expands.
This expanded material is what we use for insulation.
4. Because more iron than oxygen is in the bag, the oxygen is used
up first. The reaction can be regenerated by letting in more
oxygen.
This chemical hand warmer is similar to the hand warmers sold in
sporting goods stores.
-----------
376 RAILWAY FOOT WARMERS HEATED BY ACETATE OF SODA. [Foreign Abstracrts]
Railway Foot Warmers heated by Means of Acetate of Soda.
(Annales Industrielles, February 29,1880, col. 260.)
Minutes of Proceedings of The Institution of Civil Engineers: With
Other Selected and Abstracted Papers
Vol. LXI London 1880
The principle of this foot warmer for railway trains, designed by M.
Ancelin, is based on the employment of a body in solution, from
which a considerable quantity of latent heat is disengaged. in
passing into the crystalline state. Acetate of soda, selected for the
purpose by M. Ancelin, absorbs, in dissolving, a large quantity of
heat, which is disengaged when on cooling the salt is crystallized.
The foot warmer is charged with a solution of the acetate, and is;
then sealed up permanently. The foot warmer, is heated in a,
stove maintained at 212o Fahr., and is then placed in the carriage.
It requires from 12 to 15 hours before the crystallization of the salt
is completed, and the giving forth of heat ceases; after which it is,
again placed in the stove and re heated, at the same time
dissolving. the crystals of acetate of soda.
The new system of foot warmer is now in course of trial in express
trains on the Paris, Lyons, and Mediterranean railway.
D. K. C.
[The CRC Handbook list the heat of solution of sodium acetate as -4,140 cal/mole]
-----
Trigger to controllably initiate crystallization Imants P. Kapralis et all
Patent number: 4460546
Filing date: Aug 11, 1980
Issue date: Jul 17, 1984
Inventors: Imants P. Kapralis, Harry Krukle
http://tinyurl.com/4f7wgca
A trigger usable in initiating crystallization of a supercooled salt
solution comprises a thin metallic strip containing multiple pin-
hole size openings, and which is bendable with snap
displacement.The strip may typically be non-ferrous.
Interesting idea - as manufacturer'd these sucked as hand
warmers, the iron/salt ones work OK. (My opinion based on the one I own.)
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Magpie
lab constructor
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Very good, Wizard!
The little fiber pouches come sealed in an outer plastic bag. To activate the pouch it is removed from the outer bag and shaked. This must allow
aerial oxygen to permeate the fibrous primary bag. It is still warm some 1/2 hour later.
[Edited on 15-1-2011 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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ScienceSquirrel
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You could have written that up in ten lines using your own words instead of posting another huge slew of quotes that most people will never read.
I read the first few lines of a post. After that I will only continue if it is really interesting or it is immediately useful. There is too much
information out there to read it all.
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paulr1234
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Personally, I'm just irritated at being misled by the title of the post =)
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Magpie
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I see your point. But I would have posted that in Whimsy. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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The WiZard is In
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| Quote: Originally posted by Magpie | Very good, Wizard!
The little fiber pouches come sealed in an outer plastic bag. To activate the pouch it is removed from the outer bag and shaked. This must allow
aerial oxygen to permeate the fibrous primary bag. It is still warm some 1/2 hour later.
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This must allow aerial oxygen to permeate the fibrous primary bag.
And Moisture.
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The WiZard is In
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| Quote: Originally posted by ScienceSquirrel | You could have written that up in ten lines using your own words instead of posting
another huge slew of quotes that most people will never read.
I read the first few lines of a post. After that I will only continue if it
is really interesting or it is immediately useful. There is too much
information out there to read it all. |
Hey ... no problem. Just take you TS Card down the hall to the
Chaplains office and they will punch it for you.
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psychokinetic
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I had in my possession a hottie that turned out to be HCl + NaOH.
Real safe.
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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DougTheMapper
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Anhydrous MgSO4 and water is another good one.
Victor Grignard is a methylated spirit.
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hissingnoise
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A snowball fight, when it's so cold you need a hydraulic press to get the crystals to stick, is great for the virtual warming of hands!
Last time my hands felt like they were radiating heat *and* light!
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Random
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I was doing Cu(Oac)2 + NaCl + Al reaction during the cold day, it was useful for heating my hands too
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