The city council shall at the same time appropriate, from the remaining amount of tax levy of such year and from revenue to be derived from all other sources available for such purposes, money and credits of the city and set the same aside to funds to be designated department funds. The department funds shall be of the same number and of the same designation as the departments into which the government of the city is divided for administration under the commission form of government. The amount so appropriated and set aside to each of the funds respectively shall be an amount deemed sufficient and necessary to take care of the expenses in such department for the fiscal year or biennial period for which the appropriation is made. The amount thus appropriated to each of such departments respectively may be divided and subdivided for the purpose of expenditure as the council may direct, but shall be the maximum amount which may be appropriated to any such department for the fiscal year or biennial period, or which may be expended for the purpose of such department for the fiscal year or biennial period. Any transfer of duties or burdens of one department to another, after an appropriation has been made, shall carry with it a just and equitable pro rata proportion of the appropriation. The amounts so appropriated to the several department funds shall be used only for the purpose of paying the expenses and liabilities for which appropriated. The city council shall, at the time of the appropriation, estimate the total credits available from taxes levied and other sources for municipal purposes for the fiscal year or biennial period, and the amount remaining after deducting therefrom the amounts appropriated for statutory and department funds shall be the miscellaneous expense fund. The money and credits in the miscellaneous expense fund may be used from time to time to pay the miscellaneous expenses and obligations of the city for which an appropriation has not been made or which are not properly included within the purposes of the appropriation to any of the other funds.