The Collaborative International Dictionary of English v.0.48:

Dephlegmation \De`phleg*ma"tion\, n. [Cf. F. d['e]flegmation.]
   (Chem.)
   The operation of separating water from spirits and acids, by
   evaporation or repeated distillation; -- called also
   concentration, especially when acids are the subject of it.
   [Obs.]
   [1913 Webster]