1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 125:2011Natural rubber latexconcentrate Determinationof alkalinityBS ISO 125:2011 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 12
2、5:2011. Itsupersedes BS ISO 125:2003 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/50, Rubber - Raw, natural and synthetic, includinglatex and carbon black.A list of organizations represented on this committee can beobtained on request to its secr
3、etary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. BSI 2011ISBN 978 0 580 74668 0ICS 83.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was publish
4、ed under the authority of theStandards Policy and Strategy Committee on 30 November 2011.Amendments issued since publicationDate Text affectedBS ISO 125:2011Natural rubber latex concentrate Determination of alkalinityLatex concentr de caoutchouc naturel Dtermination de lalcalinit ISO 2011Reference n
5、umberISO 125:2011(E)Sixth edition2011-11-15ISO125INTERNATIONAL STANDARDBS ISO 125:2011ISO 125:2011(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,
6、including photocopying and microfilm, without permission in 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
7、 in Switzerlandii ISO 2011 All rights reservedBS ISO 125:2011ISO 125:2011(E) ISO 2011 All rights reserved iiiContents PageForeword iv1 Scope 12 Normative references .13 Principle .14 Reagents 15 Apparatus 26 Sampling 27 Procedure 27.1 General .27.2 Potentiometric titration 27.3 Titration using a vis
8、ual indicator 28 Expression of results .29 Precision 310 Test report .3Annex A (informative) Precision statement .4Bibliography .5BS ISO 125:2011ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of pr
9、eparing 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. International organizations, governmental and non-governmental, i
10、n 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 the rules given in the ISO/IEC Directives, Part 2.The main task
11、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 by at least 75 % of the member bodies casting a vote.Attention i
12、s 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 125 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 3, Raw materia
13、ls (including latex) for use in the rubber industry.This sixth edition cancels and replaces the fifth edition (ISO 125:2003), which has been technically revised. The main changes are the following: instructions have been included in Clause 4 for standardizing the HCl solution used; more detailed ins
14、tructions have been included in Clause 7 for the titration using a visual indicator; the precision data have been moved to an informative annex.ISO 125:2011(E)iv ISO 2011 All rights reservedBS ISO 125:2011INTERNATIONAL STANDARD ISO 125:2011(E)Natural rubber latex concentrate Determination of alkalin
15、ityWARNING Persons using this International Standard should be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices an
16、d to ensure compliance with any national regulatory conditions.1 ScopeThis International Standard specifies a method for the determination of the alkalinity of natural rubber latex concentrate.The method is not necessarily suitable for latices from natural sources other than Hevea brasiliensis or fo
17、r synthetic rubber latices, compounded latex, vulcanized latex or artificial dispersions of rubber.NOTE A method for the determination of the alkalinity of polychloroprene latex is specified in ISO 13773 (see the Bibliography).2 Normative referencesThe following referenced documents are indispensabl
18、e for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 123, Rubber latex SamplingISO 976, Rubber and plastics Polymer dispersions and rubber latices Det
19、ermination of pH3 PrincipleA test portion of latex concentrate is titrated with acid to pH 6 in the presence of a stabilizer to prevent coagulation, either electrometrically or with methyl red as a visual indicator. The alkalinity is calculated from the quantity of acid required.4 ReagentsDistilled
20、water or water of equivalent purity shall be used wherever water is specified.4.1 Stabilizer solution: 5 % (by mass) solution of a non-ionic stabilizer of the alkyl phenol polyethylene oxide condensate type. Before use, the pH of the solution shall be adjusted to a value of 6,0 0,05.The following re
21、agents shall be of recognized analytical quality:4.2 Sulfuric acid, c(H2SO4) = 0,05 mol/dm3, or hydrochloric acid, c(HCl) = 0,1 mol/dm3, standard volumetric solution.Standardize the 0,1 mol/dm3HCl by pipetting 10 ml of 0,05 mol/dm3Na2CO3solution (4.4) into a flask and titrating with the 0,1 mol/dm3H
22、Cl, using methyl orange (4.5) as indicator.4.3 Methyl red, 0,1 % solution in ethanol of minimum purity 95 % (by volume). ISO 2011 All rights reserved 1BS ISO 125:20114.4 Sodium carbonate solution, c(Na2CO3) = 0,05 mol/dm3.Dry the Na2CO3used to prepare this solution at 120 C 5 C for 2 h before prepar
23、ing the solution.4.5 Methyl orange, 0,1 % solution in ethanol of minimum purity 95 % (by volume).5 ApparatusStandard laboratory equipment together with:5.1 Electric stirrer, with earthed (grounded) motor and non-metallic propeller-type blade, or magnetic stirrer.5.2 pHmeter, equipped with a combined
24、 electrode suitable for use in solutions up to pH 12, as specified in ISO 976, and capable of being read to 0,02 pH-units.5.3 Balance, capable of being read to 0,01 g.6 SamplingCarry out sampling in accordance with one of the methods specified in ISO 123.7 Procedure7.1 GeneralCarry out the determina
25、tion in duplicate.To about 200 cm3of water in a 400 cm3beaker add, while stirring, 10 cm3of stabilizer solution (4.1).Weighing to the nearest 10 mg, add by difference from a weighing bottle between 5 g and 10 g of the latex concentrate and stir until thoroughly mixed.Ensure that the latex is added s
26、o that none runs down the side of the beaker (which could result in loss of ammonia) or down the side of the weighing bottle.Titrate the resulting mixture either by the method described in 7.2 or by that described in 7.3.7.2 Potentiometric titrationInsert the electrode of the pH-meter and, with cont
27、inual stirring, add from a burette sulfuric acid or hydrochloric acid solution (4.2), adding the acid drop by drop on approaching the end point of pH 6,0 0,05.7.3 Titration using a visual indicatorAdd 2 or 3 drops of methyl red (4.3) to the mixture and titrate with 0,1 mol/dm3HCl (see 4.2), taking a
28、s the end point the colour change from yellow to pink.8 Expression of results8.1 Depending on whether the latex concentrate has been preserved with ammonia or potassium hydroxide, calculate the alkalinity as specified in 8.2 or 8.3, respectively.ISO 125:2011(E)2 ISO 2011 All rights reservedBS ISO 12
29、5:20118.2 If the latex concentrate is preserved with ammonia, calculate the alkalinity as the percentage (by mass) of ammonia (NH3) in the latex concentrate, as follows:Alkalinity (as NH3) = F cVm1whereF1is a factor: 1,7 for hydrochloric acid or 3,4 for sulfuric acid;c is the actual concentration, e
30、xpressed in moles of HCl or H2SO4per cubic decimetre of acid used;V is the volume, in cubic centimetres, of acid used;m is the mass, in grams, of the test portion.Report the result as the mean of the duplicate determinations. If the individual results differ by more than 0,01 units from the mean whe
31、re the actual alkalinity is above 0,5 units, or by more than 0,005 units from the mean where the actual alkalinity is 0,5 units or less, repeat the determination.8.3 If the latex is preserved with potassium hydroxide, calculate the alkalinity as the percentage (by mass) of potassium hydroxide in the
32、 latex concentrate, as follows:Alkalinity (as KOH) = F cVm1whereF1is a factor: 5,61 for hydrochloric acid or 11,22 for sulfuric acid;c, V and m are as defined in 8.2.Report the result as the mean of the duplicate determinations. If the individual results differ by more than 0,015 units from the mean
33、, repeat the determination.9 PrecisionSee Annex A.10 Test reportThe test report shall include the following information:a) a reference to this International Standard;b) all details necessary to identify the test sample;c) the mean of the determinations, and the units in which it is expressed;d) full
34、 details of any incident likely to have affected the result;e) full details of any operation not included in this International Standard or in any of the International Standards to which reference is made, together with details of any operation regarded as optional;f) the date of the test.ISO 125:20
35、11(E) ISO 2011 All rights reserved 3BS ISO 125:2011Annex A (informative) Precision statementA.1 The precision of this method has been determined in accordance with ISO/TR 9272. Refer to ISO/TR 9272 for terminology and other statistical details.A.2 The precision data are given in Table A.1. The preci
36、sion parameters shall not be used for acceptance or rejection of any group of materials without documentation stating that the parameters are applicable to those particular materials and specific test protocols that include these test methods. The precision is expressed on the basis of a 95 % confid
37、ence level for the values established for repeatability r and reproducibility R.A.3 The results contained in Table A.1 are average values and give an estimate of the precision of this test method as determined in an interlaboratory test programme carried out in 2001 and including 13 laboratories per
38、forming triplicate analyses on two samples A and B which were prepared from high-ammonia latex. Before the bulk was subsampled into 1 l bottles labelled A and B, it was filtered and homogenized by thorough stirring. Thus, essentially, samples A and B were the same and were treated as such in the sta
39、tistical computations. Each participating laboratory was required to carry out the test, using these two samples, on the dates given to them.A.4 A Type 1 precision was evaluated based on the method of preparation of the latex samples used for the interlaboratory test programme.A.5 Repeatability: The
40、 repeatability r (in measurement units) of the test method has been established as the appropriate value tabulated in Table A.1. Two single test results, obtained in the same laboratory under normal test method procedures, that differ by more than the tabulated r (for any given level) shall be consi
41、dered to have come from different, or non-identical, sample populations.A.6 Reproducibility: The reproducibility R (in measurement units) of the test method has been established as the appropriate value tabulated in Table A.1. Two single test results, obtained in different laboratories under normal
42、test method procedures, that differ by more than the tabulated R (for any given level) shall be considered to have come from different, or non-identical, sample populations.A.7 Bias: In test method terminology, bias is the difference between an average test value and the reference (or true) test pro
43、perty value.Reference values do not exist for this test method since the value (of the test property) is exclusively defined by the test method. Bias cannot therefore be determined for this particular method.Table A.1 Precision dataAverage resultsWithinlaboratory Between laboratoriessrr sRR0,64 0,00
44、7 0,02 0,013 0,04r = 2,83 srwhere r is the repeatability (in measurement units) and sris the within-laboratory standard deviation.R = 2,83 sRwhere R is the reproducibility (in measurement units) and sRis the between-laboratory standard deviation.ISO 125:2011(E)4 ISO 2011 All rights reservedBS ISO 12
45、5:2011Bibliography1 ISO/TR 9272, Rubber and rubber products Determination of precision for test method standards2 ISO 13773, Rubber Polychloroprene latex Determination of alkalinityISO 125:2011(E) ISO 2011 All rights reserved 5BS ISO 125:2011ISO 125:2011(E) ISO 2011 All rights reservedICS 83.040.10P
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