The moneys realized from the sale of bonds under the provisions of sections 108.900 to 108.914 shall be paid into the state treasury, to the credit of the “Third State Building Fund”, and shall be appropriated by the general assembly for the purposes for which the bonds are authorized to be issued and for the payment of all necessary expenses incidental thereto. In making direct purchases of commodities and expending funds from the third state building fund for commodities, the commissioner of administration shall give preference to all commodities manufactured, mined, produced or grown within the state of Missouri and to all firms, corporations or individuals doing business as Missouri firms, corporations or individuals, when quality is equal or better and delivered price is the same or less.