1、DEUTSCHE NORM Auaust 199% Determining the pH of aqueous extracts of paper, board and pulp DIN 53124 - ICs 85.040; 85.060 Supersedes November 1988 edition. Papier, Pappe und Zellstoff - Bestimmung des pH-Wertes in wssrigen Extrakten In keeping with current practice in standards published by the Inter
2、national Organization for Standardization (ISO), a comma has been used throughout as the decimal marker. Foreword This standard has been prepared by Technical Committee Chemische und chemisch-technologische Prf- verfahren fr Papier, Halbstoff und Chemiezellstoff of the Normenausschuss Materialprfung
3、 (Materials Testing Standards Committee). Amendments This standard differs from the November 1998 edition in that the pH values of the standard buffer solutions have been changed and the standard has been editorially revised. Previous editions DIN 531 24: 1960-1 2, 1988-1 1. 1 Scope This standard sp
4、ecifies a method of determining the pH value of aqueous extracts of paper, board and pulp (with the exception of paper used for electrical purposes) having a conductivity exceeding 0,2 mS/m when determined as specified in DIN 531 14. It should be noted that the pH value does not provide quantitative
5、 information on the acid or alkali content of the extracted sample. For high purity papers designed for electrical purposes, the method described in IEC 554-2 should be used. NOTE: The method specified does not provide a satisfactory product characterization for multilayer, coated, faced or metalliz
6、ed paper or samples the surface of which has been modified by other methods. If the pH value at the surface is of importance forthe assessment of such products, it should be measured electrometrically using measuring cells as specified in Zellcheming-Merkblatt V/17/80 *). *) Obtainable from Verein d
7、er Zellstoff- und Papier-Chemiker und -Ingenieure, Berliner Allee 56, 64295 Darmstadt, Germany. Continued on pages 2 to 4. Translation by DI N-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text. No pari of this translation may be reproduced w
8、ithout the prior permission of V Deutsches Institut fr Nonung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, s the exclusive right of sale for German Standards (DIN-Nonen). Ref. No. DIN 53124 : 1998-0 English price group 05 Sales No. 0105 05.01 COPYRIGHT DIN DEUTSCHES Institut Fur Normung
9、E.V.- EnglishLicensed by Information Handling ServicesPage 2 DIN 531 24 : 1998-08 2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. These norma- tive references are cited at the appropriate places in the text, and the titles of the
10、publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies. DIN 53114 DIN EN 20
11、287 DIN EN 20638 DIN EN IS0 186 IEC 554-2 Merkblatt V/17/80 Determining the conductivity of aqueous extracts of paper, board and pulp (IS0 6587 : 1980, modified) Paper and board - Determination of moisture content by the oven-drying method (IS0 287 : 1985) Pulps - Determination of dry matter content
12、 (IS0 638 : 1978) Sampling of paper and board to determine average quality (IS0 186 : 1994) Specification for cellulosic papers for electrical purposes - Part 2: Methods of test Prfung von Papier, Karton und Pappe -Elektrometrische Messung des pH- Wertes auf der Oberfl2che von Papier (Testing of pap
13、er, board and pulp - Electrometric measurement of the pH value at the surface of paper)*) 3 Principle After extracting 2 g of sample for one hour with 1 O0 mi of cold or boiling distilled water, the pH of the extract is measured at a temperature of 20 “C to 25 “C. 4 Reagents 4.1 Water Only distilled
14、 or deionized water shall be used throughout the test. The conductivity of the water shall not exceed 0,l mS/m after boiling and cooling as specified in subclause 7.1.2 (see note 2). NOTE 1 : Usually, both distillation and deonization of the water is required. Unless great care is exercised when dis
15、tilling, especially with the condenser material and, consequently, with the surfaces with which the con- densed vapour comes into contact, the distillate will not reach the required conductivity. If deionized water is used without distillation and if ionization has been carried out without using a s
16、trongly basic ion exchange resin, a buffer effect may occur due to the presence of organic acids. Water produced by high-purity systems may also be used without distillation. NOTE 2: If water of the required purity cannot be obtained, water having a higher conductivity may be used, but this shall be
17、 referred to in the test report. The following reagents shall be used. 4.2 Standard buffer solutions, having pH values of 4,0, 7,O and 9,2, prepared as described in the Appendix if not commercially available. 4.3 3 mol/l potassium chloride solution, used for storing the measuring cells. 5 Apparatus
18、In addition to standard laboratory equipment, the following shall be used. 5.1 Glassware made of chemically resistant glass, comprising conical flasks, fitted with NS 29 ground glass joints and stoppers, beakers and water-cooled reflux condensers. All glassware shall be carefully rinsed with boiling
19、 distilled water and dried before use. 5.2 5.3 5.4 Thermometer. Electrical hotplate, capable of being controlled. pH meter, having pH scale intervals of 0,05. *) See page 1 for *). COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling ServicesPage 3 DIN 53124 : 1
20、998-08 6 Sampling and sample preparation During sampling and sample preparation, clean cotton gloves shall be worn to protect the sample and the pieces prepared from it. 6.1 Sampling Sampling of paper and board shall be carried out as specified in DIN EN IS0 186 and the samples of pulp shall be as r
21、epresentative as possible. 6.2 Sample preparation Tear or cut the sample into pieces measuring approximately 5 mm x 5 mm, being careful not to touch them with bare hands and ensuring that the pieces are placed only on clean surfaces. Mix the pieces carefully, avoiding any contact with the bare hands
22、. Store the pieces in clean and sealed containers. 6.3 Determining the dry matter content Determine the dry matter content of paper and board as specified in DIN EN 20287 and that of pulp as specified in DIN EN 20638. 7 Procedure 7.1 Preparing the aqueous extract 7.1.1 Weighing the sample After dete
23、rmining the dry matter content using a separate sample (see subclause 6.2), weigh, to an accuracy of 0,l g, sample pieces equivalent to 2 g of air-dried material into a conical flask of suitable size and proceed as described in subclause 7.1.2 or 7.1.3. 7.1.2 Hot extraction Pipette 100 mi of water i
24、nto a flask the same size as that containing the sample pieces. Mount the reflux condenser and heat the water to boiling, then remove the reflux condenser and transfer the boiling water to the flask containing the sample pieces. Replace the reflux condenser and boil gently for one hour. Without remo
25、ving the reflux condenser, cool rapidly to between 20 “C and 25 “C, then decant the extract into a small beaker after the fibres have settled. Prepare two extracts of each sample in parallel. 7.1.3 Cold extraction Pipette 1 O0 mi of water into a conical flask and add the sample pieces. Seal the flas
26、k with aground glass stopper and allow it to stand at 20 “C to 25 “C for one hour, shaking it occasionally. Decant the extract into a small beaker. 7.2 Determining the pH value Calibrate the pH meter using at least two buffer solutions having pH values lying on either side of that of the extract. Ri
27、nse the measuring cells several times with water and once with a small amount of extract. After ensuring that the temperature of the extract is between 20 “C and 25 “C, immerse the measuring cell in the extract and read off the pH when the reading stabilizes, usually within two minutes. NOTE 1: Duri
28、ng the pH measurement, potassium diffuses out of the calomel electrode thus affecting the conductivity. Consequently the hot extract may be used to determine the conductivity as specified in DIN 531 14 only if the sample was taken before determining the pH value. NOTE 2: Unless otherwise specified b
29、y the manufacturer, store the measuring cell in a 3 movi potassium chloride solution. Carry out a parallel test using a further extract. 8 Expression of results Report the pH value to the nearest 0,l as the mean of two tests. If the single values differ by more than 0,2, repeat the test and report b
30、oth the mean and all the individual results. 9 Test report The test report shall refer to this method and include the following details: a) all the necessary information for characterizing the sample; b) whether hot or cold extraction was used; c) the test results; COPYRIGHT DIN DEUTSCHES Institut F
31、ur Normung E.V.- EnglishLicensed by Information Handling ServicesPage 4 DIN 531 24 : 1998-08 d) the conductivity of the water used if greater than 0,l mS/m; e) any unusual observations made during the test; f) any details relating to the procedure not described in this standard, any operations regar
32、ded as optional and any circumstances which may have affected the result; g) the number of tests, if more than two. Appendix A Preparing the standard buffer solutions A.l General Only reagents of known analytical purity shall be used and the buffer solutions shall be replaced at least once a month.
33、A.2 Solution having a pH of 4,O 0,05 moM potassium hydrogenphthalate, prepared by dissolving 10,21 g of potassium hydrogenphthalate, KHC8H,0, in distilled water in a 1 O00 mi volumetric flask, diluting and making up to the mark. The pH value of this solution will be 4,OO at 20 “C and 4,Ol at 25 “C.
34、A.3 Solution having a pH of 7,O Potassium dihydrogenphosphate/disodium hydrogenphosphate, prepared by dissolving 3,54 g of potas- sium dihydrogenphosphate, KH,PO, and 5,82 g of disodium hydrogenphosphate, Na,HPO, in distilled water in a 1 O00 mi volumetric flask, diluting and making up to the mark.
35、The pH value of this solution will be 7,OO at 20 “C and 6,98 at 25 “C. A.4 Solution having a pH of 9,2 0,Ol mol/l disodium tetraborate solution, prepared by dissolving 3,8 g of disodium tetraborate decahydrate, Na,B,O, x 1 O H,O, in distilled water in a 1 O00 mi volumetric flask, diluting and making up to the mark. The pH value of this solution will be 9,23 at 20 “C and 9,18 at 25 “C. COPYRIGHT DIN DEUTSCHES Institut Fur Normung E.V.- EnglishLicensed by Information Handling Services
