BS ISO 6588-2-2012 en_8755 Paper board and pulps Determination of pH of aqueous extracts Hot extraction《纸、纸板和纸浆.水提物pH值的测定.热萃取》.pdf

1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication BS ISO 6588-2:2012 Paper, board and pulps Determination of pH of aqueous extracts Part 2: Hot extractionBS ISO 6588-2:2012 BRITISH STANDARD National foreword This British Stan

2、dard is the UK implementation of ISO 6588-2:2012. It supersedes BS ISO 6588-2:2005, which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PAI/11, Methods of test for paper, board and pulps. A list of organizations represented on this committee can be obtain

3、ed on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2012. Published by BSI Standards Limited 2012. ISBN 978 0 580 76711 1 ICS 85.040; 85.060 Compl

4、iance with a British Standard cannot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2012. Amendments issued since publication Date T e x t a f f e c t e dBS ISO 6588-2:2012 ISO 2012 Paper,

5、board and pulps Determination of pH of aqueous extracts Part 2: Hot extraction Papier, carton et ptes Dtermination du pH des extraits aqueux Partie 2: Extraction chaud INTERNATIONAL STANDARD ISO 6588-2 Second edition 2012-11-01 Reference number ISO 6588-2:2012(E)BS ISO 6588-2:2012ISO 6588-2:2012(E)i

6、i ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing f

7、rom either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 6588-2:2012ISO 6588-2:2012(E) ISO 2012 A

8、ll rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Principle 1 4 Reagents 2 5 Apparatus and equipment 2 6 Sampling and preparation of sample 2 6.1 Sampling . 2 6.2 Preparation of sample. 2 7 Procedure. 2 7.1 Weighing . 3 7.2 Extraction 3 7.3 Determ

9、ination of pH 3 8 Calculation 3 9 Test report . 3 Annex A (informative) Preparation of some standard buffer solutions 5 Annex B (informative) Precision . 6 Bibliography 8BS ISO 6588-2:2012ISO 6588-2:2012(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation o

10、f national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. In

11、ternational organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with

12、the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval

13、 by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 6588-2 was prepared by Technical Committee

14、 ISO/TC 6, Paper, board and pulps. This second edition cancels and replaces the first edition (ISO 6588-2:2005), which has been technically revised. The major difference compared with the previous edition is the addition of a paragraph in the scope to differentiate the results obtained with this sta

15、ndard from those obtained using ISO 29681 5 . ISO 6588 consists of the following parts, under the general title Paper, board and pulps Determination of pH of aqueous extracts: Part 1: Cold extraction Part 2: Hot extractioniv ISO 2012 All rights reservedBS ISO 6588-2:2012ISO 6588-2:2012(E) Introducti

16、on Kraft fibre is well known to contain ionisable groups that are fixed to or in the fibre wall. In order to fulfil the electro-neutrality, these groups are balanced by an equivalent number of positive charges, which can be either protons or various metal ions. Especially in pulp suspensions at low

17、ionic strengths, this can give rise to a marked uneven distribution of mobile ions between the volume held by the fibre wall and the bulk suspension liquor. This means that the fibre acts as an ion exchanger. These ion-exchange phenomena can be modelled very well with the Donnan theory 2, 3 . If a r

18、elatively clean pulp fibre sample, as for example bleached dried pulp, is diluted in deionised water, the result will be a pulp suspension with a very low ionic strength. In such a system, most of the cations present, including protons, will be concentrated in the water volume held by the fibre wall

19、. If the pH is measured, it will be measured in the bulk suspension liquor. By adding salt to this kind of system, the ion exchange phenomena will be decreased and the concentration of different cations will be the same in the water held by the fibre wall and in the bulk suspension liquor. Since the

20、 process waters always contain a certain amount of ions, such a salt addition will give a more realistic environment when measuring the pH of relatively clean pulp samples. It is necessary to be aware of these effects when interpreting the measured pH-values of highly purified pulps. ISO 2012 All ri

21、ghts reserved vBS ISO 6588-2:2012BS ISO 6588-2:2012Paper, board and pulps Determination of pH of aqueous extracts Part 2: Hot extraction 1 Scope This part of ISO 6588 specifies a method for the determination of the pH-value defined by the electrolytes extractable by hot water from a sample of paper,

22、 board or pulp. This part of ISO 6588 is applicable to all kinds 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 measurement

23、s on water containing little electrolytic material. Since the extraction in this part of ISO 6588 is performed with distilled or deionised water, the pH-value measured will sometimes be different (e.g. fully bleached pulp) from the pH-value measured under mill process conditions in which various typ

24、es of process waters, e.g. chemically treated river water containing electrolytes, are used. It is necessary to be aware that the results will not be the same when measuring pH according to this part of ISO 6588 when compared to ISO 29681. The differences can be significant especially when measuring

25、 pulps having a low ionic strength. ISO 6588-1 differs from this part of ISO 6588 only as regards the extraction conditions. No general guidance can be given as to which of the two procedures (hot or cold) is best suited in a particular situation. For cellulosic papers used for electrical purposes,

26、the method used should be that given in IEC 60554-2 (see 4 in the Bibliography). 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the r

27、eferenced document (including any amendments) applies. ISO 186, Paper and board - Sampling to determine average quality ISO 3696, Water for analytical laboratory use Specification and test methods ISO 7213, Pulps Sampling for testing 3 Principle Extraction of a sample of 2 g for 1 h with 100 ml of b

28、oiling 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. INTERNATIONAL ST ANDARD ISO 6588-2:2012(E) ISO 2012 All rights reserved 1BS ISO 6588-2:2012ISO 6588-2:2012(E) 4 Reagents 4.1 Wate

29、r, 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 rang

30、e of 6,8 to 7,3. Instructions for the determination of conductivity are specified in ISO 3696. 4.2 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 des

31、cribed, in Annex A. 4.3 Potassium chloride solution, 1M. Dissolve 7,4 g of KCl, analytical grade, in 100 ml of freshly boiled, distilled water. Prepare a fresh solution every week. 5 Apparatus and equipment Use the following, in addition to ordinary laboratory apparatus and equipment. 5.1 Glassware

32、of chemically resistant glass, flasks with ground-glass joints, stoppers, beakers, reflux condenser 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 (4.1) and allowed to dry be

33、fore use. 5.2 pH-meter, fitted with glass and calomel electrodes or with a combined electrode, capable of being read to at least 0,05 pH-unit. 6 Sampling and preparation of sample 6.1 Sampling The sampling procedure to be followed depends on the particular circumstances in each case. If the analysis

34、 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 s

35、pecimen 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. 6.2 Preparation of sample Do not touch the sample w

36、ith bare hands and ensure that it has been placed only on clean surfaces. Cut or tear the sample into pieces approximately 1 cm 2in size with a clean knife or a cutter. Split samples of heavy board. Mix the pieces thoroughly. Store the pieces in clean, covered containers. 7 Procedure Run the procedu

37、re in duplicate.2 ISO 2012 All rights reservedBS ISO 6588-2:2012ISO 6588-2:2012(E) 7.1 Weighing Weigh 2,0 g 0,1 g of air-dry sample (6.2). NOTE Since the amount of sample is not critical, there is no need to determine the dry matter content to adjust for minor differences in moisture content. 7.2 Ex

38、traction Add 100 ml of water (4.1) to a 250 ml flask (5.1) and heat to boiling. Add the weighed sample, attach the reflux condenser (5.1) fitting the flask, and continue boiling gently for 1 h 5 min on an electric heater. Cool the flask rapidly to a temperature between 20 C and 25 C with the condens

39、er in place. Filter the extract through a coarse, fritted glass filter into a small beaker (5.1). Immediately add 2 ml of potassium chloride solution (4.3) and continue with the measurement. 7.3 Determination of pH Operate the pH-meter in accordance with the manufacturers instruction. Wash the elect

40、rodes with water (4.1); allow the water to drain from the electrodes, but do not wipe them. Calibrate the pH-meter (5.2), at a temperature between 20 C and 25 C, with two different buffer solutions (4.2) having pH- values such that the pH of the extract is between the pH-values of the buffer solutio

41、ns. The first buffer solution should be chosen so that the pH-value of the buffer solution is in the same region as the electric zero point of the pH-meter (usually = 7). The reading for the second buffer solution should agree with its correct value to within 0,1 pH-unit. If the pH-meter fails to sh

42、ow the correct pH-value for the second buffer solution, consult the manufacturers manual. A deviation exceeding 0,2 pH-units indicates a faulty electrode. Also a slow but continuous increase or decrease in the reading indicates faulty electrodes. After calibration, rinse the electrode several times

43、with water (4.1) and once in a small quantity of the extract. Check that the temperature of the extract is between 20 C and 25 C. Immerse the electrodes in the extract. Record the pH when there is no measurable drift, within 30 s. Before measuring the next sample, rinse the electrodes carefully with

44、 water (4.1) to remove any traces of sample or buffer solution. At the end of a series of measurements, check the electrodes with buffer solutions. 8 Calculation Calculate the mean of the duplicate determinations. Report the pH-value to the nearest 0,1 pH-unit. The individual results should not diff

45、er by more than 0,2 pH-unit; if they do, repeat the determination with two additional extracts, and report the mean and the range of all measurements. 9 Test report The test report shall include the following information: a) a reference to this part of ISO 6588; b) the date and place of testing; c)

46、all the information necessary for complete identification of the sample; d) the result, expressed as indicated in Clause 8; e) any unusual features observed in the course of the test; ISO 2012 All rights reserved 3BS ISO 6588-2:2012ISO 6588-2:2012(E) f) any departure from the procedure described in

47、this part of ISO 6588, or any other circumstances which may have affected the result.4 ISO 2012 All rights reservedBS ISO 6588-2:2012ISO 6588-2:2012(E) Annex A (informative) Preparation of some standard buffer solutions All the reagents used shall be of recognized reagent grade. The buffer solutions

48、 shall be renewed at least 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 solution Dissolve 10,21 g of potassium hydrogen phthalate (KHC 8 H 4 O 4 ) in water (4.1) in a 1 litre volumetric flask and dilute

49、 to the mark. The pH-value of this solution is 4,00 at 20 C and 4,01 at 25 C. A.2 Buffer solution pH 6,9: potassium dihydrogen phosphate and disodium hy- drogen phosphate solution Dissolve 3,39 g of potassium dihydrogen phosphate (KH 2 PO 4 ) and 3,54 g disodium hydrogen phosphate (Na 2 HPO 4 ) in water (4.1) 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 25 C. A.3 Buffer solution pH 9,2: disodium tetraborate solution Dissolve 3,80 g