Aberdeen keeper Langfield was sent off at the very end of the first half by referee Craig Charleston after Killie midfielder Borja Perez had dived in the penalty box to win a penalty.
While the decision to give the spot kick is up to the referee, Charleston made an obvious error of judgement with the red card decision.
Perez did not have a clear goalscoring opportunity, there were defenders between him and the goal, and the little Spanish rat was heading away from goal when he collapsed like a fairy.
SFA rules are clear on the matter of so-called 'last man' red cards, and Langfield's did not fall into that category even if you accept that the dive was indeed a penalty.
A message on the club's official website RedWeb simply says: "The club can confirm they will be appealing the red card given to Jamie Langfield during the game with Kilmarnock on Saturday."