32 Degree Thermochomic dye [closed]








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I am doing a school project which involves color changing based off of temperature, and I need a thermochromic dye that changes color at 32 degrees Fahrenheit. Does anyone know where I could find some or explain how it is made? 




You might try a solution of cobalt(II) chloride, $\ce{CoCl2}$, [in plain water](http://chem.lapeer.org/Chem2Docs/CobaltChlorideEq.html) (which might freeze) or in a mixture of water and ethanol or water and isopropyl alcohol. At some concentration, which you'd experimentally determine, it should turn from pink to blue on cooling to 273 K. See [Flinn Scientific's site](https://www.flinnsci.com/api/library/Download/bfff7c565e7d4b59a3b82114674d7aa5) for more details.


BTW, you might as well use [Réaumur](https://en.wikipedia.org/wiki/R%C3%A9aumur_scale) as Fahrenheit; both are provincial.


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