I have seen people claim that putting salt in coffee enhances the flavour or removes bitterness. Example.
Does this really work? If it does, how does it work? Is there something chemical going on, or is it just a trick of the taste-buds?
In a Good eats episode from the 13th season (The Ballad of Salty and Sweet), Alton Brown explains how salt (specifically the sodium) blocks your tongue's taste buds from sensing bitterness. Sweetness however is not blocked. It also is known to enhance other flavours. Salt on chocolate is awesome for example. Salt also has the ability to still taste salty while doing all the rest.