Chemical Christmas decorations

Hi.

I wish you happy Christmas and I have for you small Christmas experiment . It's very easy make this, but sometimes it takes little patience. I don't know exact amount of chemicals, but this isn't important.

I made four colorchanging chemical Christmas decorations today from my stock solutions of K2CrO4, CoCl2 and CuSO4.

1. Make cca 30ml of 2,5% solution of CuSO4.5H2O, add small amount of H2SO4 (just to prevent hydrolysis) and heat it on hot water bath. Then add solid NaCl in to the solution until it turns green. After that cool it in cold water bath to room temperature. It change colour in to turquoise. If solution have still green colour, add dropwise some water.

2. Make cca 30ml of 2,5% solution of CuSO4.5H2O, add small amount of H2SO4 (just to prevent hydrolysis) and heat it on hot water bath. Then add solid KBr in to the solution until it turns brown. After that cool it in cold water bath to room temperature. It change colour in to green. If solution have still brown colour, add dropwise some water.

3. Make cca 20ml of 1,5% solution of CoCl2.6H2O, add cca 10-15ml of concentrated HCl and heat it. Then add solid NaCl in to the solution until it turns blue. After that cool it in cold water bath to room temperature. It change colour in to red with purple hue. If solution have purple colour, add dropwise some water.

4. Make cca 30ml of 1,5% solution of K2CrO4, add 1-3 drops of 5% NH3 solution and some solid NH4NO3 or (NH4)2SO4. Solution have yellow colour, but it isn't typical chromate yellow. Heat in on hot water bath. Solution change colour in to orange. If not, add dropwise some 5% acetic acid. Upon acidification you must cool solution in to room temperature. Cold solution must have yellow colour, if not, add again dropwise NH3, heat it and check again colour of hot solution. I made my K2CrO4 solution from K2Cr2O7 and KOH, so there was very small excess of KOH, so for me it was little laborious find good balance. NH3/NH4+ works as buffer.

These four solutions change their colour with temperature. Colorchange works for eternity, so you may repeat it when you want. It's beautiful Christmas decoration .

Thanks to woelen for inspiration to make chromate/dichromate decoration .

Explanation:

1. [Cu(H₂O)₆]²⁺ + 3Cl^- <--> [Cu(H₂O)Cl₃]^- + 5H₂O

[Cu(H₂O)Cl₃]^- + Cl^- <--> [CuCl₄]^2- + H₂O

2. [Cu(H₂O)₆]²⁺ + 3Br^- <--> [Cu(H₂O)Br₃]^- + 5H₂O

[Cu(H₂O)Br₃]^- + Br^- <--> [CuBr₄]^2- + H₂O

3. [Co(H₂O)₆]²⁺ + 4Cl^- <--> [CoCl₄]^2- + 6H₂O

4. 2CrO₄^2- + H₂O <--> Cr₂O₇^2- + 2OH^-

With increasing temperature equilibrium shifts more to the right.



[Edited on 24-12-2019 by Bedlasky]

My rainbow salts series.

Purple: it looks more purple in real life, tetraamminecopper(II) sulfate, from basic copper carbonate

Blue: copper(II) sulfate, from basic copper carbonate

Orange: potassium dichromate, from chromium metal

Yellow: under preparation, potassium chromate, from chromium metal

Green: under preparation, nickel(II) chloride, from pure nickel coins

Red: no idea lol

Quote: Originally posted by Bedlasky

Red: cobalt salts are red in colour. Or nickel bis(dimethylglyoximate).

Quote: Originally posted by Bedlasky

Artemov: I saw chloride and sulfate, both have very nice red colour, but I never saw acetate and nitrate.

Quote: Originally posted by sciece nerd

CoCl2 is more of a reddish purple, and CoSo4 is more red but it's closer to light red in powder form (between pink and red) but larger crystals is darker, more red.

It's really quite hard to find true bright red salts ...

Quote: Originally posted by artemov

It's really quite hard to find true bright red salts ...

What about Reinecke's salt?

Possibly one of the nices reds I have ever had.

Quote: Originally posted by Diachrynic

Quote: Originally posted by artemov   It's really quite hard to find true bright red salts ... What about Reinecke's salt? Possibly one of the nices reds I have ever had.

I took a look of my CoSO4, and I realized it's very red, with a hint of orange, I think it's close enough to bright red for collecting, I think the photo on Wikipedia displayed it's color quite accurately.




[Edited on 7-1-2021 by sciece nerd]

Quote: Originally posted by sciece nerd

I took a look of my CoSO4, and I realized it's very red, with a hint of orange, I think it's close enough to bright red for collecting, I think the photo on Wikipedia displayed it's color quite accurately. [Edited on 7-1-2021 by sciece nerd]

Thanks ... I just ordered some malonic acid and barium nitrite to try making some violuric acid and dimethylglyoxime. Hopefully their derivatives will be red

Quote: Originally posted by Housane

What procedure are you following for the violuric acid prep?