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Radiums Lab
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Thermochromism at human body temperature?
Hi guys, so I was recently working with some ZnO and TiO2 which had a beautiful colour changing effect.
I am aware that HgI2, ZnS etc. do the same thing.
My question is :
Are there any compounds which exhibit thermochromism at human body temperatures(preferably inorganic ones).
I was struck with this idea when my gallium melted in a sealed vial due to the heat of my hand.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Radiums Lab
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Please note that the examples which I gave change colour at high temperatures.
[Edited on 9-7-2025 by Radiums Lab]
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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bnull
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Check mood rings.
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phlogiston
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There must be, because there are lots of products that produce a range of colors at this range. Mouse pads, etc.
a friend also used to have a thermochromic-paint-based thermometer sticker on an aquarium, which IIRC was around the 30 degree C range, so it changes
colors between room temperature and human body.
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Radiums Lab
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Thank you @phlogiston and @bnull for replying, after a bit of digging I failed to find material used
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Fulmen
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You can't have tried that hard: https://en.wikipedia.org/wiki/Thermochromism
First image on the page: https://en.wikipedia.org/wiki/File:Liquid_crystals.webm
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Radiums Lab
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@Fulmen thank you for the link(how did I miss wiki). Any inorganic compounds which show the same?
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Fulmen
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I have no idea. These liquid crystals have been around for decades, but i have never heard of anything else that does anything similar.
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bnull
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It seems that inorganic substances need higher temperatures to show thermochromism. Aqueous dichromate/chromate and alcoholic copper(ii) chloride (I
believe aqueous too) change color if you heat them. I considered making sealed samples to use as thermometers for test tubes but never got around to
measure the temperature range. Copper(i) iodide gets orange or yellow above 60 °C.
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Radiums Lab
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Hi bnull, so can we conclude no such inorganic salts exist showing thermo. at human temperature.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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bnull
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I didn't say that. There may exist at least one inorganic substance, in solid state or in solution, that changes color at 30-40 °C. The thing is, I
don't know such substance but I can't rule out its existence. I'd bet on transition metal salts, either pure or combined with other salts, oxides
included (remember the superconductors, they're usually mixed oxides).
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Radiums Lab
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Chat gpt and wiki don't have any answers about an inorganic version so I think it's time for a new discovery.
Reminds me of that potassium metal thread.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Lionel Spanner
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I found at least one example of organic thermochromism, due to keto/enol tautomerism, though it occurs over a wider range of temperatures.
https://www.nature.com/articles/171222a0
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Radiums Lab
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Yea you are right there are many organic ones but they are not easy to synth that is why Inorganic .
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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chempyre235
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It seems that several alkyl ammonium tetrahalonickelate salts are thermochromic near room temperature, with
[(Me)2NH2]2NiCl4 transitioning at 110°C. Nickel can form these salts with any halogen, and some
pseudohalogens. Not 100% inorganic, but the anion is, at least. Besides this, Et2N can be had relatively simply from hydrolysis of DEET.
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Organic ammonium salts of the type (R3NH)2NiCl4 are often thermochromic (R = Me, Et, Pr)...The corresponding
tetrabromonickelates are also thermochromic with a lower transition temperatures.
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Copper salts appear to react similarly to nickel ones, and at least one cuprate, (Et2NH2)2CuCl4, is
thermochromic at even lower temps. Additionally, it seems that zinc and other transition metals (Mn, Fe, Co, Cd and Hg) form these tetrahedral,
tetrahalogenic anions in much the same way. Might be worth investigating.
https://en.wikipedia.org/wiki/Thermochromism
https://en.wikipedia.org/wiki/Tetrachloronickelate
https://en.wikipedia.org/wiki/Transition_metal_chloride_comp...
[Edited on 7/12/2025 by chempyre235]
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
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Radiums Lab
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Yea Ni compounds should be looked into.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Neal
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Surprised no 1 said cobalt chloride. Blue/pink. But it has to be in HCl or acid though.
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Radiums Lab
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Temperature at which colour changes?
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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j_sum1
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Yeah, but that would be an equilibrium between two different complex ions. Colour change for sure, but not thermochromism.
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Neal
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Quote: Originally posted by j_sum1  |
Yeah, but that would be an equilibrium between two different complex ions. Colour change for sure, but not thermochromism. |
So the temperature changes the pH, which changes the color? I see. I was wondering if the HCl is acting like a sensitizer.
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DraconicAcid
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| Quote: Originally posted by Neal | | Quote: Originally posted by j_sum1 |
Yeah, but that would be an equilibrium between two different complex ions. Colour change for sure, but not thermochromism. |
So the temperature changes the pH, which changes the color? I see. I was wondering if the HCl is acting like a sensitizer. |
No. You have the equilibrium along the lines of
[Co(H2O)6]2+ + 2 Cl- <===> [Co(H2O)2Cl2] + 4 H2O
(octahedral, pink) (tetrahedral, blue)
You need a high concentration of chloride ion to get reasonable concentrations of the tetrahedral complex, but the equilibrium constant is
temperature-dependent. You can add chloride until the solution is purple, then heat it up to turn it blue, or cool it down to make it pink.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Fulmen
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Apoptosis just dropped a video on inorganic thermochromics:
https://www.youtube.com/watch?v=GvcXcOpuEec
Nothing within body temperatures though, but 50C isn't half bad either.
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Radiums Lab
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Yea Fulmen thank you for notifying me about his recent vedio, so 50 degrees is pretty close. The vedio is pretty cool.
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Fulmen
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Just don't poison yourself, mercury compounds are nasty.
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Lionel Spanner
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For what it's worth, when I carried out a Jones oxidation of an alcohol to an acid, back in my first year of university (20 years ago) I ended up with
a thermochromic impurity, which was red around 80 °C and green near room temperature.
This was a chromium compound of some kind, for sure - but I don't remember what the alcohol was, so when all's said and done, this post is not
actually very helpful.
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