The Collaborative International Dictionary of English v.0.48:

Euchlorine \Eu*chlo"rine\, n. [Cf. F. euchlorine. See
   Euchloric.] (Chem.)
   A yellow or greenish yellow gas, first prepared by Davy,
   evolved from potassium chlorate and hydrochloric acid. It is
   supposed to consist of chlorine tetroxide with some free
   chlorine. Euchologion