The Collaborative International Dictionary of English v.0.48:

Cyamellone \Cy*am"el*lone\ (s[-i]*[a^]m"[e^]l*l[=o]n), n. (Chem)
   A complex derivative of cyanogen, regarded as an acid, and
   known chiefly in its salts; -- called also hydromellonic
   acid.
   [1913 Webster]