The washings and mother liquor were collected separately because of unreacted Ac2O in the filtrate.
http://www.thieme-chemistry.com/thieme-chemistry/journals/info/show_pdf.html?thieme-chemistry/journals/info/include/pdf/synthesis/errata_ss_9906.pdf (http://www.thieme-chemistry.com/thieme-chemistry/journals/info/show_pdf.html?thieme-chemistry/journals/info/include/pdf/synthesis/errata_ss_9906.pdf)