72 Pa. Stat. § 5981
The treasurers of the several counties in this commonwealth shall be, and they are hereby respectively authorized and directed to commence on the second Monday in June, in the year 1816, and at the expiration of every two years thereafter, and adjourn from day to day, if it shall be found necessary so to do, and make public sale of the whole or any part of such tracts of unseated lands, situate in the proper county, as will pay the arrearages of the taxes, any part of which shall then have remained due and unpaid for the space of one year before, together with all costs necessarily accruing by reason of such delinquency, and to make and execute a deed or deeds, in fee simple, in the manner directed by the act to which this is a further supplement.
72 P.S. § 5981