The county treasurer of every county, except counties of the first class, shall adjourn or readjourn, to such time or times, not later than the first Monday of August, one thousand nine hundred and thirty-nine, all tax sales on seated and unseated lands for nonpayment of taxes. Where any such tax sales are adjourned or readjourned after advertisement, an additional advertisement and notice shall be necessary for such adjourned or readjourned sale. No such adjournment or readjournment shall invalidate the lien of any tax due and unpaid or any penalties or interest due thereon, but the lien of all such taxes shall remain in full force and effect until such sale shall take place in accordance with this act.