No contract for work to be done for, or property or material to be sold or supplied to, such city, or any department thereof, shall be made with any councilman, officer, or employe of such city, or with any firm, copartnership, or association of which such councilman, officer, or employe is a member, and if any councilman, officer, or employe, during the term for which he shall have been elected or appointed, knowingly acquire an interest in any such contract, he shall forfeit his office or position.
53 P.S. § 12673