AS NZS 1301.421:2020 pdf free download – Method of test for pulp and paper Method 421: Paper, board and pulps -Determination of pH of aqueous extracts-Cold extraction

AS NZS 1301.421:2020 pdf free download – Method of test for pulp and paper Method 421: Paper, board and pulps -Determination of pH of aqueous extracts-Cold extraction.
This document specifies a method for the determination of the pit-value defined by the electrolytes extractable by cold water from a sample of paper, board or pulp.
This document is applicable to all types of paper, board and pulp.
As the quantity of extractable ionic material approaches zero, as in the case of highly purified puips. the precision of the method becomes poor because of the difficulties encountered in making pit measurements on water containing little electrolytic material.
Since the extraction in this document is performed with distilled or deiuniscd water, the pH-value measured will sometimes be different (e.g. for fully bleached pulp) from the p11-value measured under mill process conditions in which various types of process waters, e.g. chemically treated river water containing electrolytes, are used. In such cases, ISO 29681 should be used instead, as It is specifically applicable to bleached puips from virgin fibres and to pulp samples having a low ionic strength for which the pH value will give more realistic results related to mill conditions than those obtained with this document.
Forcellulosic papers used forelectrical purposes, the method used should be thatgiven in IEC 60554-2141.
2 Normative references
The following documents are referred to In the text In such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 16, Paper and board — Sampling to determine average quality
ISO 7213. Pulps — Sampling for testing
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platforni: available at https-j/wwwlso.orgJobp
— IEC Electropedia: available at https;/Iwww.iso.or2lobp
4 Principle
Extraction of a sample of 2 g for 1 ii with 100 ml of cold water of high purity. Filtration of the extract and addition of a salt solution, Measurement of the pH-value of the extract at a temperature between 20 °C and 25 C.
All the reagents used shall be of recognized reagent grade. The buffer solutions shall be renewed atleast once a month.The anhydrous salts in A.1 and A.2 shall be dried at 120 °C.
A.1 Buffer solution pH 4,0: Potassium hydrogen phthalate,0,05 mol/l solutionDissolve 10,21 g of potassium hydrogen phthalate(KHCgH404) in water (5.1) in a 1 litre volumetricflask and dilute to the mark.
The pH-value of this solution is 4,00 at 20 C and 4,01 at 25 °℃.
A.2 Buffer solution pH 6,9: Potassium dihydrogen phosphate and disodiumhydrogen phosphate solution
Dissolve 3,39 g of potassium dihydrogen phosphate (KH>POa) and 3,54 g disodium hydrogen phosphate(NazHPO4) in water (5.1) in a 1 litre volumetric flask and dilute to the mark.
The pH-value of this solution is 6,87 at 20 C and 6,86 at 25C.
A.3 Buffer solution pH 9,2: Disodium tetraborate solution
Dissolve 3,80 g of disodium tetraborate decahydrate (NagB40710H20) in water (5.1) in a 1 litrevolumetric flask and dilute to the mark.
The pH-value of this solution is 9,23 at 20 C and 9,18 at 25C.