Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: huwston on 12/01/2007 21:48:32

Title: copper sulphate
Post by: huwston on 12/01/2007 21:48:32

 i want to make very large CuSO4 crystal.

scraps of copper are easy to find here in the uk.

would leaving copper pieces in car battery acid for long enough, make a decent concentration and yield for a tennis ball sized crystal(if they can grow that big), provided i had enough copper?
 

Title: copper sulphate
Post by: rosy on 12/01/2007 22:40:52

I rather doubt copper will dissolve in battery acid (copper oxide would dissolve more readily). You'd need a vast volume of solution... and copper is pretty toxic (two readily accessible oxidation states, google for the fenton reaction).
Look up the solubility of copper sulphate, the density of solid copper sulphate and work out the volume you'd need if all the CuSO₄ in the solution ended up on this vast crystal. Which it won't, I don't think... it'll make beautiful, smaller crystals all over the sides of your container.
 

Title: copper sulphate
Post by: huwston on 13/01/2007 00:03:16

what if i managed to make a strong enough solution and made seed crystals.
i could grow a crystal from a thread of cotton i like have done with NaCl.

would this work?

Title: copper sulphate
Post by: daveshorts on 13/01/2007 11:22:42

It is certainly possible to grow crystals of CuSO₄ in the same way as you did with NaCl, as I made a few as a kid at home. My dad had a bag of CuSO₄ left over from when it was sold as a fungicide. If you want to make a really large crystal, you are going to have to contend with small crystals forming instead of the main one. I guess you have to be very careful about concentrations and temperatures although you would probably still have to regularly weed out small crystals and recycle them.

Title: copper sulphate
Post by: rosy on 13/01/2007 11:42:57

I think attempting to concentrate sulfuric acid by distillation will actually just drive off SO₃
And sulphuric acid ain't nice, if you leave 10% solution on paper it chars, and battery acid is 33%.
http://ptcl.chem.ox.ac.uk/MSDS/SU/sulfuric_acid_concentrated.html
I'll have a look to see if I can find anywhere you could just buy copper sulphate.

Title: copper sulphate
Post by: daveshorts on 13/01/2007 11:46:28

Try a gardening shop to get hold of it eg:
http://www.gardenchemicals.co.uk/pdt_coppersulphate.htm
it is for some bonkers reason considered an organic fungicide
- it is a heavy metal salt, and not particularly nice, the only possible reason that it could be considered organic is that they used it a hundred years ago - but they used Arsenic a hundred years ago as an insecticide.... If the organic movement was actually looking at different chemicals and deciding which were best for the environment I wouldn't mind, but just trying to take us back to the 19th century seems crazy.

Title: copper sulphate
Post by: huwston on 13/01/2007 12:24:32

cheers, thanks for your help.

£5 for 100 or 200g of CuSO4 is a bit steep.

electroplating websites have it for £10 for a 5 litre mix , it contains about a kilo of it or something.