Chemistry experiment 37 - Temperature dependent color

The color of a cobalt sulfate solution in the presence of chloride ions is dependent on temperature.

[@sidewaysfcs0718]

just to clarify, this is not a thermochromic material (which actually changes color whitout undergoing a chemical reaction) , what is happening here is a chemical reaction triggered by temperature. initially, in the copper sulphate solution you have [Co(H2O)6]2+ ions, which appear pink (it's moslty absorbing green light) , then when you heat up the solution, you are substituting the 6 water ligands for 4 chloride ligands, producing the [CoCl4]2- ion, which appears blue ( it's absorbing mostly orange light) .

[@susantarakshit6515]

everything is right except the name of the complex. its not copper sulphate.

[@chemistrywithmuhamad5732]

Very good

[@Pahkthacaaa]

if I were to do this with students, could I heat the test tube in a hot water bath to achieve the color change, or is something like a blowtorch needed in order to achieve the color change? great video by the way

[@checkbordspy4608]

Thanks I've been looking for something like this for ever for a magic trick, is it safe to put on clothes and can I change the coulours it turns into

[@ordaflo]

no, you don't want to mess with cobalt

[@prachitpereira7752]

How long will this chemical process work..?

[@shahidmahmood7046]

good