The clerk shall keep a convenient set of books in which there shall be kept a separate account with each collecting officer of the city or town. He shall keep a separate account with each department for which a separate appropriation shall have been made, crediting the amount of the appropriation and charging warrants drawn against the same. He shall keep such other accounts as may be necessary to show the financial condition of the municipality and of each department thereof at all times. He shall not allow the amount appropriated for any item of expense to be drawn on for any other purpose. He shall not allow any warrant to be drawn unless sufficient funds actually be in the treasury to the credit of the fund upon which such warrant is drawn unless specifically authorized by an ordinance.