The commissioner of taxation and finance shall be the custodian of the special fund for disability benefits and all disbursements therefrom shall be paid by him upon drafts signed by the chairman or those authorized by the chairman for that purpose. The commissioner of taxation and finance shall give a separate and additional bond in an amount to be fixed by and with sureties approved by the state comptroller conditioned for the faithful performance of his duty as custodian of the fund. The commissioner of taxation and finance shall deposit any portion of the fund not needed for immediate use, in the manner and subject to all the provisions of law respecting the deposit of other state funds by him. The commissioner of taxation and finance may invest any surplus or reserve moneys thereof in securities of the United States or the state of New York and in interest bearing certificates of deposit of a bank or trust company located and authorized to do business in this state or of a national bank located in this state secured by a pledge of direct obligations of the United States or of the state of New York, or in accordance with the provisions of section ninety-eight-a of the state finance law, in an amount equal to the amount of such certificates of deposit, and may sell any such securities or certificates of deposit if advisable for the proper administration of such fund. Interest earned by such portion of the fund deposited or invested by the commissioner of taxation and finance shall be collected by him and placed to the credit of the fund. The commissioner of taxation and finance may issue checks on the fund for the transfers of moneys between depositories and for the purpose of making investments for the fund.