Abstract： AS/NZS 1301.421:2020 pdf download.Method of test for pulp and paper Method 421: Paper, board and pulps -Determination of pH of aqueous extracts-Cold extraction. 5 Reagents 5.1 Water, distilled or deionised water shall be used throughout the...

AS/NZS 1301.421:2020 pdf download.Method of test for pulp and paper Method 421: Paper, board and pulps -Determination of pH of

aqueous extracts-Cold extraction.

5 Reagents

5.1 Water, distilled or deionised water shall be used throughout the test. The conductivity of the water shall not exceed 0,1 mS/m. after boiling for 1 h and cooling in an acid-free atmosphere (e.g. free of COz. 502, H2S) to a temperature between 20°C and 25

°C. The pH of the water should be in the range of 6,8 to 7,3. Instructions for the determination of conductivity are specified

in ISO 3696.

5.2 Standard buffer solutions, with known pH-values of about 4, 7 and 9. Such buffer solutions are commercially available. Some

examples of suitable buffer solutions are given, and their preparation Is described, In Annex k

5.3 Potassium chloride solution, 1M. Dissolve 7.4 g of KCI, analytical grade, into 100 ml of freshly boiled, distilled water.

Prepare a fresh solution every week.

6 Apparatus and equipment

Use the following, in addition to ordinary laboratory apparatus and equipment.

6.1 Glassware of chemically resistant glass, flasks with ground.glass joints, stoppers, beakers and trifled glass filter. All glassware shall he cleaned with an acid cleaning solution, without the use of soap or detergent, and they shall be carefully rinsed with water (5.1) and allowed to dry before use.

6.2 pH-meter, fitted with glass and caloniel electrodes or with a combined electrode, capable of being read to at least 0,05

pH-unit.

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