One participating without employment or authority in a transaction resulting in an exchange of property is not entitled to a commission. Merrill v. Latham, 8 Colo. App. 263, 45 P. 524. See also Sec. 17.

Where broker was employed by one party to a trade, that the other secured a benefit from the broker's services in the selling of his property would not authorize inference that there was an implied promise to pay a commission. Yockum v. Gassett, 200 S. W. 582, - Tex. Civ. App. - .