Pulps — Determination of Kappa number
Pulps — Determination of Kappa number
ISO 302:2015 specifies a method for the determination of the Kappa number of pulp. The Kappa number is an indication of the lignin content or bleachability of pulp. ISO 302:2015 is applicable to all kinds of chemical pulps and semi-chemical pulps within the Kappa number range 1 to 100. For pulps with a Kappa number exceeding 100, use the chlorine-consumption procedure (ISO 3260) to describe the degree of delignification. To achieve the greatest precision and accuracy, the sample size has to be adjusted so that the consumption of permanganate falls between 20 % and 60 % of the amount added. NOTE There is no general and unambiguous relationship between the Kappa number and the lignin content of pulp. The relationship varies according to the wood species and delignification procedure. All compounds oxidized by KMnO4, not only lignin, will increase the consumption of KMnO4, and thereby increase the Kappa number.[8] If the Kappa number is to be used to derive an index of pulp lignin content, specific relationships will have to be developed for each pulp type.
ISO 302:2015 specifies a standardized laboratory method for determining the Kappa number of pulp - an indicator of pulp lignin content and bleachability. The method covers chemical and semi‑chemical pulps with Kappa numbers from 1 to 100. For pulps with Kappa numbers above 100, ISO 3260 (chlorine‑consumption procedure) is recommended. The test is based on controlled oxidation of pulp with potassium permanganate (KMnO4), quenching with potassium iodide, and titration of released iodine with sodium thiosulfate.
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Keywords: ISO 302:2015, Kappa number, pulp testing, KMnO4, lignin content, bleachability, pulp analysis, ISO standard.