[FlaskBreaker]

Yesterday afternoon, I was observing the decomposition of some basic copper(II) carbonate that I made, when I noticed my ceramic evaporating dish rapidly turning black on the outside. The inside, however, stayed the same cream-ish color. Is this normal for ceramic evaporating dishes and crucibles? What is causing this?

I bought my evaporating dish from Home Science Tools.

Thanks,
FB

[chenbeier]

copper carbonate would decompose to copper-II-oxide at high temperature. This has black color.

[FlaskBreaker]

The black color was on the outside of the evaporating dish, so this couldn't be the CuO product. I will post a picture when I get the chance.

[billnotgatez]

My first guess is that the inside and outside of your evaporating dish is coated or manufactured differently.

It is possible that some vapors in your home lab interacted with the outside.

My second guess is that the CuO experiment somehow protected the inside of the evaporating dish.

We can guess forever.

Maybe you can test an other evaporating dish of the same kind that is no where near you CuO experiment.

Is that not what experimenting is about.

[Borek]

How were heating the dish?

[FlaskBreaker]

I have confirmed that it was a thin layer of carbon that deposited on the dish. The alcohol burner I was using must not burn very cleanly.