Australia's Science Forum

Hi All,

Our year 7's are doing their famous crystallisation prac with copper sulphate & alum. Every year we have beakers with crystals adhered to the glass. Does anybody have an easy way to remove the crystals?

Cheers,
Hel

I just soak in water - or maybe rinse under hot tap. Don't remember having too many problems.

I agree with the above, just rinse, don't force the crystals and leave to soak overnight if your not in a hurry to re-use the glassware.

Hot water usually loosens them up without too much effort.


Julie

Use plastic take away containers??

If the kids haven't filtered their copper sulphate solution very well, then a brown tinge can develop on the glass. I have a supply of hydrochloric acid that I use to rinse them and they come up beautifully. The acid can be reused many times but I wouldn't use it for anything else.
Cheers
Jen

Hi,

We use plastic drink tumblers and find that this is much easier with the cleaning.

Sandyd

Did this prac only once using beakers to crystallise copper sulfate/alum solution. Told teachers afterwards that they would be using disposable plastic petri dishes to recrystallise the solutions. Students let their solutions cool a little before pouring liquid into the petri dishes. The results are good and we save the best samples of crystals. Recycle the other dishes for a variety of uses.
Lyn.

Thanks everyone. The plastic tumblers & petri dishes sound like a good idea for the future.