1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 776:2011Pulps Determination of acid-insoluble ashBS ISO 776:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 776:2011. It supers
2、edes BS 4496:1984, which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee PAI/11, Methods of test for paper, board and pulps.A list of organizations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 obtained on request to its secretary.This publication does not purport to
3、 include all the necessary provisions of a contract. Users are responsible for its correct application. BSI 2011 ISBN 978 0 580 68302 2 ICS 85.040 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards
4、 Policy and Strategy Committee on 30 November 2011.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 776:2011Pulps Determination of acid-insoluble ashPtes Dtermination des cendres insolubles dans lacide ISO 2011Reference numberISO 776:2011(E)Third edition2011-08-15ISO776INTERNATI
5、ONAL STANDARDBS ISO 776:2011ISO 776:2011(E)COPYRIGHT PROTECTED DOCUMENT ISO 2011All 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 i
6、n writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in Switzerlandii ISO 2011 All rights reservedBS ISO 776:2
7、011ForewordISO (the International Organization for Standardization) is a worldwide federation of 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
8、 technical committee has been established has the right to be represented on that committee. International 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 matte
9、rs of electrotechnical standardization.International Standards are drafted in accordance with 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 circulate
10、d to the member bodies for voting. Publication as an International Standard requires approval 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 f
11、or identifying any or all such patent rights.ISO 776 was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.This third edition cancels and replaces the second edition (ISO 776:1982), which has been technically revised. The ignition temperature has been changed from 575 C to 525 C to be
12、 consistent with the temperature specified in ISO 1762. The method also requires that the minimum mass of acid-insoluble residue be 10 mg instead of 1 mg, in order to improve the accuracy of the test.ISO 776:2011(E) ISO 2011 All rights reserved iiiBS ISO 776:2011IntroductionAcid-insoluble ash consis
13、ts primarily of silica and silicates. This material, when present in the finished paper or paperboard, can have an abrasive effect on punches, knives, slitters and dies which come into contact with paper during finishing operations. Paper made from pulps with more than 400 mg/kg (based on oven-dried
14、 mass) of acid-insoluble ash can cause premature dulling of such equipment. The level of silica in pulp can vary significantly depending on several factors, including wood type, water quality, and the presence of silicate-based additives, such as clay and talc. For example, in bleached kraft pulps,
15、the silica mass fraction can range from under 100 mg/kg to over 1 000 mg/kg.ISO 776:2011(E)iv ISO 2011 All rights reservedBS ISO 776:2011INTERNATIONAL STANDARD ISO 776:2011(E)Pulps Determination of acid-insoluble ash1 ScopeThis International Standard specifies a method for the determination of the a
16、cid-insoluble ash of pulp. It is applicable to all types of pulps.2 Normative referencesThe 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 referenced docume
17、nt (including any amendments) applies.ISO 638, Paper, board and pulps Determination of dry matter content Oven-drying methodISO 1762, Paper, board and pulps Determination of residue (ash) on ignition at 525 CISO 7213, Pulps Sampling for testing3 Terms and definitionsFor the purposes of this document
18、, the following terms and definitions apply.3.1acid-insoluble ashinsoluble residue remaining after a pulp sample is ignited in a furnace at 525 C 25 C and the ash treated with hydrochloric acid as specified in this International Standard4 PrincipleA test specimen is weighed in a heat-resistant conta
19、iner, ignited in a muffle furnace at 525 C 25 C, and the residue is treated with hydrochloric acid. The insoluble residue after acid treatment is filtered, washed, ignited at 525 C and weighed. The moisture content of a separate test portion is also measured. The acid-insoluble ash is then determine
20、d, in milligrams per kilogram, on an oven-dry basis, from the mass of the insoluble residue after ignition and the dry matter content of the sample.5 ReagentUse only analytical grade reagent and distilled water or water of equivalent purity.5.1 Hydrochloric acid, 6 mol/l solution.Carefully, in a fum
21、e hood, dilute 500 ml of hydrochloric acid (density at 20 C = 1,19 kg/l) to 1 000 ml with water.6 Apparatus6.1 Heat-resistant evaporating dishes, of capacity 50 ml to 100 ml, and crucibles with a capacity of 20 ml. Platinum containers are preferred, but porcelain or silica may be used.6.2 Steam bath
22、 or electric hotplate, capable of maintaining a surface temperature of 110 C to 130 C. ISO 2011 All rights reserved 1BS ISO 776:20116.3 Analytical balance, of capacity 100 g, accurate to 0,1 mg.6.4 Desiccator.6.5 Muffle furnace, capable of maintaining a temperature of 525 C 25 C.6.6 Filter paper, qu
23、antitative, ashless, double acid-washed, of a type recommended for fine precipitates (e.g. Whatman No. 421)or equivalent).6.7 Drying oven, capable of maintaining an air temperature of 105 C 2 C and suitably ventilated.7 Sampling and preparation of test specimenIf the analysis is done in order to eva
24、luate a pulp lot, obtain a representative pulp sample as described in ISO 7213. If it is not, report the source of the sample and, if possible, the sampling procedure used. Sufficient sample shall be collected to allow for at least duplicate determinations and for the determination of moisture conte
25、nt.Obtain a test specimen consisting of small pieces, not larger than 1 cm2, from various parts of the sample in such a manner as to be thoroughly representative of it. The mass of the test portion shall be such that the mass of the acid-insoluble residue is greater than 10 mg. A test portion weighi
26、ng 25 g is sufficient in most cases.NOTE In samples with very low levels of acid-insoluble residue, it might be necessary to obtain a larger test specimen and to ignite it in more than one portion.8 ProcedureCarry out the procedure in duplicate.Condition the test specimens and moisture specimens in
27、the laboratory atmosphere until they reach equilibrium moisture.Determine the moisture content of the sample as described in ISO 638. Weigh this test portion at the same time as the test portion used for ash determination.Ash the test specimens as described in ISO 1762, in a dish previously ignited
28、in the muffle furnace, to a constant mass (to the nearest 0,1 mg). If the dish is too small to hold the entire specimen, the specimen shall be ashed in portions. Place a portion of the specimen in the dish and burn it gently to avoid any loss. Then add the next portion to the dish and burn it gently
29、. Continue this process until the entire specimen has been carbonized, as indicated by the absence of black carbon particles.Cool the dish to room temperature in a fume hood, add 5 ml of 6 mol/l HCl (5.1), and evaporate carefully to dryness on a steam bath or hotplate (6.2). Repeat the treatment. Ad
30、d a third 5 ml aliquot of 6 mol/l HCl (5.1) to the residue, heat for 2 min on the steam bath or hotplate, and dilute with 20 ml of water.Quantitatively transfer the residue by filtering through the filter paper (6.6), being careful to remove all the residue from the dish with water. Wash the residue
31、 several times with hot water until the filtrate is free of chloride ions.The absence of chloride ions in the filtrate may be confirmed with a few drops of 5 % silver nitrate. The filtrate should not produce a white precipitate or opalescence.Carefully place the filter paper and residue into a tared
32、 20 ml crucible or heat-resistant evaporating dish (6.1). Heat gently until dry, then ignite at 525 C 25 C until the entire specimen has been ashed, as indicated by the absence of black carbon particles. Cool the crucible in a desiccator and weigh to the nearest 0,1 mg. Repeat the ignition until a c
33、onstant mass is obtained.1) Whatman No. 42 is an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of this product.ISO 776:2011(E)2 ISO 2011 All rights reservedBS ISO 776:20119 C
34、alculationCalculate the mass fraction of acid-insoluble ash according to Equation (1):wmma= 100012(1)wherewais the mass fraction of acid-insoluble ash, expressed as milligrams per kilogram of the oven-dry sample;m1is the mass of insoluble residue after ignition at 525 C 25 C, in milligrams;m2is the
35、mass of the sample, on an oven-dry basis, in grams.Report the mean of duplicate determinations to the nearest 5 mg/kg.10 Test reportThe test report shall include the following information:a) a reference to this International Standard (ISO 776:2011);b) the date and place of testing;c) a complete iden
36、tification of the sample tested;d) the result, expressed as indicated in Clause 9;e) any departure from the procedure described in this International Standard or any other circumstances which may have affected the result.ISO 776:2011(E) ISO 2011 All rights reserved 3BS ISO 776:2011Annex A (informati
37、ve) PrecisionA.1 GeneralIn August 2009, an international round robin was performed in which eight laboratories from five different countries participated.Three samples of different types of pulp were tested. Each sample was disintegrated, to ensure its homogeneity, and made into handsheets. Several
38、handsheets from each sample were submitted to the participating laboratories for testing according to this International Standard. For the two hardwood bleached kraft pulp samples, the data from two of the eight laboratories were considered as outliers and were not included in the precision statemen
39、t.The calculations were made according to ISO/TR 24498, Paper, board and pulps Estimation of uncertainty for test methods.The repeatability and reproducibility limits reported are estimates of the maximum difference which should be expected in 19 of 20 instances, when comparing two test results for
40、material similar to those described under similar test conditions. These estimates may not be valid for different materials or different test conditions.NOTE Repeatability and reproducibility limits are calculated by multiplying the repeatability and reproducibility standard deviations by 2,77, wher
41、e 2,77 = 1,96 2 .A.2 RepeatabilityTable A.1 Estimation of the repeatability of the test methodSampleNumber of laboratoriesMean valueStandard deviationCoefficient of variationRepeatability limitmg/kgsrmg/kgCV,r%rmg/kgHardwood bleached kraft pulp (low ash)6 1 368 72,6 5,3 201Hardwood bleached kraft pu
42、lp (high ash)6 2 909 72,4 2,5 201Clay-filled mechanical pulp furnish8 112 955 4 611 4,1 12 781ISO 776:2011(E)4 ISO 2011 All rights reservedBS ISO 776:2011A.3 ReproducibilityTable A.2 Estimation of the reproducibility of the test methodSampleNumber of laboratoriesMean valueStandard deviationCoefficie
43、nt of variationReproducibility limitmg/kgsRmg/kgCV,R%Rmg/kgHardwood bleached kraft pulp (low ash)6 1 368 112 8,2 311Hardwood bleached kraft pulp (high ash)6 2 909 165 5,7 458ISO 776:2011(E) ISO 2011 All rights reserved 5BS ISO 776:2011ISO 776:2011(E)ICS 85.040Price based on 5 pages ISO 2011 All righ
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