IS 1060 : Part 4 : Sec 7 : 2024/ISO 6588-2 : 2021 Methods of Sampling and Test for Paper and Allied Products - Part 4 Methods of Test for Paper, Board and Pulp - Section 7 Determination of pH of Aqueous Extracts - Hot Extraction Method

NATIONAL FOREWORD

This Indian Standard (Part 4/Sec 7) (First Revision) which is identical to ISO 6588-2 : 2021 'Paper, board and pulps - Determination of pH of aqueous extracts - Part 2: Hot extraction' issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on the recommendation of the Paper and its Products Sectional Committee and approval of the Chemical Division Council.

Kraft fiber, known for its ionizable groups within the fiber wall, necessitates electro-neutrality through protons or metal ions. In low ionic strength pulp suspensions, this leads to uneven ion distribution, essentially turning fibers into ion exchangers, well described by the Donnan theory.

When pure pulp, like bleached dried pulp, is mixed with deionized water, resulting suspensions exhibit minimal ionic strength, with cations mostly accumulating around fiber walls. Adding salt equalizes cation concentrations between fiber wall water and suspension liquor, providing a more accurate representation of process water ions for pH measurements.