Sodium borohydride - NaBH4
Sodium borohydride is a typical novelty chemical which is discovered in the 1940's and only is available commercially since the end of the 1950's. It is a strong reducing agent, which however only decomposes slowly in non-acidic aqueous solution. In acidic solution it quickly decomposes, giving hydrogen and borates. Sodium borohydride is capable of reducing many metal ions to the free metals and it also is capable of reducing ketones and aldehydes to alcohols. Organic acids, having a -COOH group, however, are not reduced and esters, having a -C(O)-O-C- group also are not reduced.
This chemical has a very strong tendency to form sticky lumps and for this reason it is really important to store it in a tightly sealed container. Even very small amounts of absorbed water cause the lumps to stick together making the handling of the chemical awkward.