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Project to analyze nickel content in British vs. American coins

I am a school pupil doing an advanced higher chemistry investigation, comparing the percentage of nickel in British coins to that in American coins. Firstly, I will dissolve the coins in nitric acid and electrolyse the solution to remove the copper. The plan is to eventually titrate the nickel solutions against a standard solution of EDTA, then work out from there the percentage of nickel in each coin. The only problem is that there will be impurities in the coins and a) I don't really know what they are and b)I don't know how to remove them. If anyone could help with these questions it would be greatly appreciated.

Thank you.

Fiona C.
School Pupil - Scotland, UK
2003

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A good project! To make steps forward I would suggest a bit of "research". Firstly look up what metals are used in coinage - you can probably find a suitable website, but if not, contact the Royal mint in Wales. Secondly, get a book on analytical chemistry that covers "spot tests". This will tell you how to identify different metals by the colours they turn different reagents. Thirdly, if you only want to analyse for nickel, use dimethyl glyoxime, it is specific for nickel and will not be interfered with by any other metal. I know that copper ions will form a deep blue solution with excess ammonia ⇦ this on eBay or Amazon [affil links] and also form a red-brown colour with in a slightly acidic solution with potassium ferrocyanide ⇦ this on eBay or Amazon [affil links] , but be careful with this test as excess ferrocyanide can destroy its sensitivity. I do not know if either test is specific for copper, so you will have to do a bit of extra work!

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003