The governing body of any city that owns or operates waterworks, gas-works, or electric plant may by ordinance establish a petty cash fund for the use of said utilities, for the purpose of paying postage, freight, temporary labor, and other emergency expenses, including refund of deposits made to secure payment of accounts. Such petty cash fund shall be deposited in the designated city depository bank and paid out on the order of the cashier of such utilities by checks which shall state clearly the purpose for which issued.