The City Council of said city is authorized to appropriate all delinquent taxes against which no demands are outstanding, and after the purposes for which said taxes were levied have been fulfilled and satisfied, to any proper municipal purpose, and the City Council is empowered at the end of each fiscal year thereafter to declare such residue of said delinquent taxes a surplus and to direct that the same, when collected, be carried in bulk, as a surplus account, subject to appropriation by the council for proper municipal purposes, under the provisions of this Charter.