A gaseous element, colorless, tasteless, and odorless,
   the lightest known substance, being fourteen and a half times lighter
   than air (hence its use in filling balloons), and over eleven thousand
   times lighter than water. It is very abundant, being an ingredient of
   water and of many other substances, especially those of animal or
   vegetable origin. It may by produced in many ways, but is chiefly
   obtained by the action of acids (as sulphuric) on metals, as zinc,
   iron, etc. It is very inflammable, and is an ingredient of coal gas and
   water gas. It is standard of chemical equivalents or combining weights,
   and also of valence, being the typical monad. Symbol H. Atomic weight
   1.