Any portion of the principal proceeds derived from the sale of the bonds which the board of directors of the authority may determine is not then needed for any of the purposes for which the bonds are authorized to be issued shall, on order of the authority, be invested by the State Treasurer in permitted investments which mature at such time or times as the authority shall direct. Any such investments may, at any time and from time to time on order of the authority, be sold or otherwise converted by the State Treasurer into cash. The income derived from any such investments shall be disbursed on order of the authority for any purpose for which it may lawfully expend funds.
Ala. Code § 41-10-507 (1975)