Sciencemadness Discussion Board

What is this yellow stuff?

ATPfactory - 13-7-2021 at 12:44

Yesterday I made some copper acetate with copper, vinegar and hydrogen peroxide. Today I wanted to evaporate the vinegar off so I'd get copper acetate crystals. I had attached a rubber hose that I put in some water to get rid of the smell from the vinegar fumes. I think the yellow stuff came from something that decomposed in the hose when the temperature got high enough. Since the hottest part of the hose lost its color. But I have no clue what it is exactly. When I was cleaning the glassware, and filled it with water, the water became yellowish and pretty cloudy. Do any of you know or have a good guess what it is?
edit: the hose is made out of latex

IMG_20210713_211214_resized_20210713_101905544.jpg - 2.3MB

[Edited on 13-7-2021 by ATPfactory]

[Edited on 13-7-2021 by ATPfactory]

vmelkon - 15-7-2021 at 21:06

My guess it is some copper compound. Perhaps you heated your liquid to drying and the edges overheated.

Amos - 16-7-2021 at 04:53

I've observed bright yellow-orange regions in solid copper(II) acetate before when it was boiled to dryness in a beaker and then heated for a little while longer. I'm really not sure what it could be, but I'm tempted to say it is some kind of copper-containing substance and not from the latex. Copper(I) oxide has a hydrated form which is that exact color, so it may be plausible that a little of your copper(II) was reduced back to copper(I) by elemental copper after most of the acid had been consumed. If you managed to collect a little bit of the yellow precipitate, you should leave it exposed to air and light and see if it turns brown and eventually black.

unionised - 16-7-2021 at 05:18

Heating copper (II) acetate will give rise to "organic stuff" and that can reduce copper (II) to copper (I) .

Syn the Sizer - 16-7-2021 at 13:58

Food grade vinegar often contains a sugar impurity. Pickling vinegar is usually sugar free as is cleaning vinegar. Maybe it is a reaction between sugar, H2O2 and copper. Just a thought.

ATPfactory - 16-7-2021 at 16:19

Quote: Originally posted by Amos  
I've observed bright yellow-orange regions in solid copper(II) acetate before when it was boiled to dryness in a beaker and then heated for a little while longer. I'm really not sure what it could be, but I'm tempted to say it is some kind of copper-containing substance and not from the latex. Copper(I) oxide has a hydrated form which is that exact color, so it may be plausible that a little of your copper(II) was reduced back to copper(I) by elemental copper after most of the acid had been consumed. If you managed to collect a little bit of the yellow precipitate, you should leave it exposed to air and light and see if it turns brown and eventually black.


I didn't collect it, but I kept heating it until almost all of the liquid was evaporated. At that point the highest part of the yellow ring had turned a bit brown with some black parts.
So you are probably right.

BackyardScience2000 - 16-7-2021 at 17:20

Agreed with what's been said already. Probably reduced to copper (I) and if food grade vinegar was used then probably some contamination as well. For future use, I would buy some lab grade glacial acetic acid and dilute to needed levels. Just a thought. :)

Fantasma4500 - 18-7-2021 at 06:55

you should try boiling a bit of the vinegar away and if it isnt brown at that point add some concentrated H2SO4, ive just boiled down a load of CuAc and nothing came out brown, CuAc is rather black with a slight blue tint

Yttrium2 - 19-7-2021 at 04:24

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