The Collaborative International Dictionary of English v.0.48:

Sociate \So"ci*ate\, a. [L. sociatus, p. p. of sociare to
   associate, fr. socius companion.]
   Associated. [Obs.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sociate \So"ci*ate\, n.
   An associate. [Obs.]
   [1913 Webster]

         As for you, Dr. Reynolds, and your sociates. --Fuller.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sociate \So"ci*ate\, v. i.
   To associate. [Obs.] --Shelford.
   [1913 Webster]