The Collaborative International Dictionary
barytum
Barium \Ba"ri*um\, n. [NL., fr. Gr. bary`s heavy.] (Chem.) One of the elements, belonging to the alkaline earth group; a metal having a silver-white color, and melting at a very high temperature. It is difficult to obtain the pure metal, from the facility with which it becomes oxidized in the air. Atomic weight, 137. Symbol, Ba. Its oxide called baryta.
Note: Some of the compounds of this element are remarkable for their high specific gravity, as the sulphate, called heavy spar, and the like. The oxide was called barote, by Guyton de Morveau, which name was changed by Lavoisier to baryta, whence the name of the metal.
Wiktionary
barytum
n. (context chemistry obsolete English) barium