I searched for copperas on google and it says ferrous sulphate. My dictionary shows that the word copperas is derived from copper.

I was just wondering what has ferrous sulphate to do with copper


1 Answer 1


You are on the right track.

The Brockhaus Konversationslexikon (Brockhaus Encyclopedia, 14th edition, 1894-1894)

explains the German term Kupferwasser (copper water) as

veraltete Bezeichnung für unreinen (kupferhaltigen) Eisenvitriol

which means outdated name for impure (copper-containing) iron vitriol.

Note that iron vitriol is an old term for iron(II) sulfate, such as vitriolic oil is an outdated name for sulfuric acid.

If you take a look at English wikipedia page on iron(II)sulfate, you'll see that one of the common minerals is a heptahydrate, melanterite. If you follow the link, you will recognize that one of the associated minerals is chalcanthite, which is $\ce{CuSO4·5H2O}$.

To cut the long story short, the term copperas stems from the fact that natural iron(II)sulfate was often found to be associated and maybe contaminated with copper(II)sulfate.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.