72 Pa. Stat. § 3641
The secretary of the commonwealth, the auditor general and the state treasurer are hereby constituted commissioners to receive the foregoing incomes and revenues, and apply the same, first to the payment of the accruing interest of the public debt, and second to the principal thereof, and not otherwise, except as provided in section four, article eleven, of the constitution of this commonwealth; and it shall be the duty of said commissioners, within ten days of the time of payment of interest upon the funded debt of the commonwealth, in the months of February and August in each year, to assign to said sinking fund such amount of surplus funds in the treasury as may not be necessary for current outlays, and may be required for the payment of said interest; and the amount so assigned shall be transferred to said sinking fund, and the account thereof kept as provided in this act.
72 P.S. § 3641