Farquhar will join the White Sox prior to Saturday's game against the Rangers.
Farquhar was called up to the big-league club just a month after being released by Tampa Bay. In 37 outings with the Rays this year, Farquhar posted a 4.11 ERA and 1.43 WHIP over 35 innings of relief. In a corresponding move, the team placed Reynaldo Lopez on the 10-day DL with a strained back.