AS NZS 1301.421 pdf download

AS NZS 1301.421 pdf download.Method of test for pulp and paper Method 421: Paper, board and pulps — Determination of pH of aqueous extracts — Cold extraction
1  Scope
This document specifies a method for the determination of the pH-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 pulps, the precision of the method becomes poor because of the difficulties encountered in making pH measurements on water containing little electrolytic material. Since the extraction in this document is performed with distilled or deionised water, the pH-value measured will sometimes be different (e.g. for fully bleached pulp) from the pH-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 pulps 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. For cellulosic papers used for electrical purposes, the method used should be that given in IEC 60554-2 [4] .
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 CO 2 , SO 2 , H 2 S) 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 KCl, 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 cm 2 in size. Split samples of heavy board. Mix the pieces thoroughly. Store the pieces in clean, covered containers.