The Collaborative International Dictionary of English v.0.48:

Hexeikosane \Hex*ei"ko*sane\, n. [Hex- + eikosane.] (chem.)
   A hydrocarbon, C26H54, resembling paraffine; -- so called
   because each molecule has twenty-six atoms of carbon.
   [Written also hexacosane.]
   [1913 Webster]