Pennsylvania Statutes Title 21 P.S. Deeds and Mortgages § 304. Powers valid until notice of revocation

No sale of lands, tenements and hereditaments made by virtue of such power or powers of attorney or agency as aforesaid, shall be good and effectual, unless such sale be made and executed while such power is in force; and all such powers shall be accounted, deemed and taken to be in force, until the attorney or agent shall have due notice of a countermand, revocation, or death of the constituent.