A warehouseman, in the absence of some lawful excuse provided by this act, is bound to deliver the grain upon a demand made either by the holder of a receipt for the grain, or by the depositor, if such demand is accompanied with: (a) An offer to satisfy the warehouseman’s lien; (b) an offer to surrender the receipt, if negotiable, with such endorsements as would be necessary for the negotiation of the receipt; and (c) a readiness and willingness to sign, when the grain is delivered, an acknowledgement that it has been delivered, if such acknowledgement is requested by the warehouseman. In case the warehouseman refuses or fails to deliver the grain in compliance with the demand by the holder or depositor so accompanied, the burden shall be upon the warehouseman to establish the existence of a lawful excuse for such refusal.