The county commissioners of the several counties of the Commonwealth, be, and they are hereby, authorized to sell at public sale, for the best price obtainable, all lands heretofore or hereafter purchased by said counties at sheriff's sales, under judgments obtained on tax claims upon which the period for redemption has expired, and to execute and deliver to purchasers proper deeds for lands so sold; notice of such sale to be given by publication in at least one newspaper of general circulation, published at the county-seat, once a week for three consecutive weeks; said notice to designate particularly the tracts to be sold.