The Collaborative International Dictionary of English v.0.48:

Congratulate \Con*grat"u*late\, v. t. [imp. & p. p.
   Congratulated; p. pr. & vb. n. Congratulating.] [L.
   congratulatus, p. p. of congratulari to wish joy abundantly;
   con- + gratulari to wish joy, from gratus pleasing. See
   Grateful.]
   To address with expressions of sympathetic pleasure on
   account of some happy event affecting the person addressed;
   to wish joy to.
   [1913 Webster]

         It is the king's most sweet pleasure and affection to
         congratulate the princess at her pavilion. --Shak.
   [1913 Webster]

   To congratulate one's self, to rejoice; to feel
      satisfaction; to consider one's self happy or fortunate.

   Syn: To Congratulate, Felicitate.

   Usage: To felicitate is simply to wish a person joy. To
          congratulate has the additional signification of
          uniting in the joy of him whom we congratulate. Hence
          they are by no means synonymous. One who has lost the
          object of his affections by her marriage to a rival,
          might perhaps felicitate that rival on his success,
          but could never be expected to congratulate him on
          such an event.
          [1913 Webster]

                Felicitations are little better than
                compliments; congratulations are the expression
                of a genuine sympathy and joy.    --Trench.
          [1913 Webster]