§ 204. Certification and approval of contracts and conveyances. No written contract providing for the payment of two hundred dollars or more, entered into by the city or any of its officers, boards or departments, shall become effective or be acted under until there shall be indorsed thereon by the corporation counsel or an assistant, a certificate to the effect that the city officer, board or department which has executed the same on behalf of the city, had authority and power to make such contract, and that such contract is in proper form and properly executed; he shall approve all deeds, conveyances, leases and abstracts of title affecting property acquired, conveyed to or leased by the city; and he shall attend to all the law business of the city and discharge such other duties as may be prescribed by law or ordinance of the common council.