The board of county commissioners authorizing the levying of such tax shall establish a special fund in the county treasury designated as the county loan fund and all moneys collected from the general tax levied for the purpose of repaying any loans, with interest, must be deposited to the credit of said special fund and may be used only for the purpose of repaying the principal, with accrued interest, due upon loans made by the county as the same matures. The balance, if any, remaining in said special fund, after the amount of the loan, with accrued interest, has been paid in full, may be transferred by the county commissioners to the general fund of the county.