ISO 29681:2009规定了测定纸、纸板和纸浆水提取物pH值的方法，其中浸泡和测量在盐水（0.1 M KCl溶液）中进行。 ISO 29681:2009适用于所有类型的纸、纸板和纸浆，但特别适用于来自未经处理纤维的漂白纸浆和具有低离子强度的纸浆样品，使用本国际标准的pH值将给出比使用ISO 6588-1或ISO 6588-2获得的与研磨条件相关的更现实的结果。

ISO 29681:2009 specifies a method for the determination of the pH of an aqueous extract of paper, board and pulps, in which the soaking and the measuring are performed in salted water (0,1 M KCl solution). ISO 29681:2009 is applicable to all kinds of paper, board and pulps, but is specifically applicable to bleached pulps from virgin fibres and to pulp samples having a low ionic strength for which the pH-value using this International Standard will give more realistic results related to mill conditions than those obtained with ISO 6588-1 or ISO 6588-2.