What chemicals are often confused for different chemicals? Recently I asked a similar question on Chinese SE: Why would Antimony (Sb) and Aluminum (Al) be confused?  



It seems, though, that this is by no means a Chinese phenomenon.

The Wiki page for Tin foil mentions that:


  aluminium foil, [...] is still referred to as "tinfoil" in many regions. 


What other chemicals are often confused for different chemicals?

I'm especially interested in things that have retained their incorrect names.
One especially serious example is confusing methanol with ethanol. Methanol is highly toxic and sometimes is deliberately added to or inadvertently present in bootleg alcoholic beverages, causing many deaths and blindness in survivors every year around the world. It would be a life saver for someone to develop a cheap dipstick test for methanol.