All contributions received by the retirement system from members and participating municipalities shall be paid periodically to the general treasurer and shall be deposited by the treasurer to the credit of the retirement system. All moneys not immediately required for the payment of retirement allowances or other benefits under the provisions of this chapter may be invested by the state investment commission under the provisions of chapter 10 of Title 35. The retirement board has full power with respect to the disposition of the proceeds of the investments and of any moneys belonging to the retirement system.