AS/NZS 1301.421:2020 pdf free.Method of test for pulp and paper Method 421: Paper, board and pulps一 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 o[the water shall not exceed 0,1 mS/rn, after boiling for 1 h and cooling in an acid-free atmosphere (e.g. free of C02, SO2, 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 A.
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 fritted glass filter. All glassware shall be 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 calomel electrodes or with a combined electrode, capable of being read to at least 0,05 pH-unit.
7 Sampling and preparation of sample
7.1 Sampling
The sampling procedure to be followed depends on the particular circumstances in each case. If the analysis is being made to evaluate a lot or a consignment of pulp, paper or board, the sample shall be taken in accordance with ISO 7213 or ISO 186, as relevant. If the analysis is made on another type of sample, report the origin of the sample and, if possible, the sampling procedure, and ensure that the specimen taken in 7.1 is representative of the sample received.
Wear clean protective gloves when handling the sample.
NOTE Some gloves are powdered to prevent them from sticking to one another, and this powder can cause
contamination of the sample.
7.2 Preparation of sample
Do not touch the sample with bare hands and ensure that it has been placed only on clean surfaces. Cut the sample with a knife or cutter, or tear it, into pieces approximately 1 cm2 in size. Split samples of heavy board.
Mix the pieces thoroughly. Store the pieces in clean, covered containers.
8 Procedure
Run the procedure in duplicate.AS/NZS 1301.421 pdf download.