BS ISO 11852-2017 Rubber -- Determination of magnesium content of field natural rubber latex by titration《橡胶 滴定法测定现场天然乳胶中镁的含量》.pdf

1、BS ISO 11852:2017Rubber Determinationof magnesium content offield natural rubber latex bytitrationBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 11852:2017 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 11852:2017. It s

2、upersedes BS ISO 11852:2011 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee PRI/50, Raw materials (including latex) for use in the rubber industry.A list of organizations represented on this committee can be obtained on request to its secretary.This pu

3、blication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2017.Published by BSI Standards Limited 2017ISBN 978 0 580 89058 1 ICS 83.040.10 Compliance with a British Standard cannot confer imm

4、unity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 April 2017.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 11852:2017 ISO 2017Rubber Determination of magnesium content of field

5、natural rubber latex by titrationCaoutchouc Dtermination par titrage de la teneur en magnsium du latex de plantation de caoutchouc naturelINTERNATIONAL STANDARDISO11852Second edition2017-04Reference numberISO 11852:2017(E)BS ISO 11852:2017ISO 11852:2017(E)ii ISO 2017 All rights reservedCOPYRIGHT PRO

6、TECTED DOCUMENT ISO 2017, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without pri

7、or written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Geneva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 118

8、52:2017ISO 11852:2017(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 15 Apparatus . 26 Reagents 27 Procedure. 38 Expression of results 49 Precision . 410 Test report . 4Annex A (informative) Precision . 5Bibliography 7 ISO 2017 All rights reserve

9、d iiiContents PageBS ISO 11852:2017ISO 11852:2017(E)ForewordISO (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. Eac

10、h 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, in liaison with ISO, also take part in the work. ISO collaborates closely with the Internation

11、al Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different

12、types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall n

13、ot be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents).Any trade name used in this document is

14、 information given for the convenience of users and does not constitute an endorsement.For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade Organizat

15、ion (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www .iso .org/ iso/ foreword .html.This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 3, Raw materials (including latex) for use in the rubber industry.This seco

16、nd edition cancels and replaces the first edition (ISO 11852:2011), which has been technically revised to be applicable only to field latex. Therefore, all references to concentrated natural rubber latex have been removed and the following changes have been made: the title of this document has been

17、changed; an introduction has been added to explain the advantages of the method described in this document; the definition of natural rubber latex concentrate has been removed from Clause 3; the determination of magnesium content of concentrated latex in Clause 5 has been deleted; because borax is a

18、 substance of high concern and reprotoxic, the buffer solution (6.4) has been changed from borax buffer solution to ammonium chloride/ammonium hydroxide buffer solution; the precision data for concentrated latex in Annex A have been deleted.iv ISO 2017 All rights reservedBS ISO 11852:2017ISO 11852:2

19、017(E)IntroductionIn this document, no additional chemical is required to mask the interference from other divalent ions. The end-point determination in this method is easily determined since most, if not all, of the interferences have been removed during the centrifugation process. Furthermore, the

20、 chemical used for masking the interference in the alternative method has an unpleasant odour.Another advantage of this document is that the centrifuge machine used in the method is already available in laboratory for desludging purposes. Hence, no additional cost is incurred by the laboratory to ca

21、rry out the test. ISO 2017 All rights reserved vBS ISO 11852:2017BS ISO 11852:2017Rubber Determination of magnesium content of field natural rubber latex by titrationWARNING Persons using this document should be familiar with normal laboratory practice. This document does not purport to address all

22、of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.1 ScopeThis document specifies a titration method for the determination of the magnesium

23、 content of field natural rubber latex. 2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest editio

24、n of the referenced document (including any amendments) applies.ISO 385:2005, Laboratory glassware BurettesISO 648:2008, Laboratory glassware Single-volume pipettes3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.ISO and IEC maintain terminological

25、databases for use in standardization at the following addresses: IEC Electropedia: available at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp3.1magnesium contentamount of magnesium, and possibly also other alkaline-earth metals, present i

26、n a sample of natural rubber field latexNote 1 to entry: When ammonia is added to field latex, the calcium and magnesium ions present in varying concentrations in the serum of the latex are, to a large extent, precipitated as ammonium phosphate complexes, which gradually settle out in the sludge. Th

27、e results of the test method described in this document are expressed as the magnesium content on the assumption, which is not strictly true, that magnesium is the only divalent alkaline-earth ion remaining in the latex after the sludge has been removed. Calcium ions are also present, occasionally i

28、n appreciable amounts.4 PrincipleThe latex is centrifuged at between 2 500 m/s2(250g) and 5 000 m/s2(500g), using a laboratory centrifuge, for 3 min. A known mass of the resultant latex, free of sludge, is diluted with water, and the residual magnesium content present in the latex is determined by t

29、itration with the disodium salt of INTERNATIONAL STANDARD ISO 11852:2017(E) ISO 2017 All rights reserved 1BS ISO 11852:2017ISO 11852:2017(E)ethylenediaminetetraacetic acid (EDTANa2) in the presence of a buffer, using Eriochrome Black T1)as indicator.This method is applicable to field latex preserved

30、 with ammonia or with a combination of ammonia and formaldehyde, in which the ammonia content on titration is not less than 0,2 % of the latex. The method determines the total concentration of divalent alkaline-earth ions remaining in the latex after the removal of sludge, and this is taken as the m

31、agnesium content.The magnesium content can be expressed either as a percentage of the mass of the latex or in milligrams per kilogram of latex.5 Apparatus5.1 Laboratory centrifuge, capable of producing an acceleration between 2 500 m/s2(250g) and 5 000 m/s2(500g).5.2 Centrifuge tubes, each of at lea

32、st 50 cm3capacity.5.3 pH-meter, equipped with a glass electrode and a saturated calomel electrode of the sleeve or sintered-disc type and capable of reading to 0,1 pH-units. Calibrate the pH-meter by using buffer solutions of pH 4,0, 7,0 and 10,0.5.4 Burette, of capacity 10 cm3or 50 cm3, complying w

33、ith the requirements of ISO 385:2005, class A.5.5 Balance, accurate to 0,1 mg.5.6 Volumetric pipette, of capacity 10 cm3, complying with the requirements of ISO 648:2008, class A.5.7 Beaker, of capacity 400 cm3.6 ReagentsUse reagents of recognized analytical grade and deionized water or water of equ

34、ivalent purity.6.1 Magnesium sulfate solution, 0,005 M.Dissolve 1,231 6 g of magnesium sulfate heptahydrate (MgSO47H2O) in water. Make up to 1 dm3in a volumetric flask. 1 cm3of this solution is equivalent to 1 cm3of 0,005 mol/dm3EDTANa2.6.2 EDTANa2solution, 0,005 M.6.2.1 PreparationDissolve approxim

35、ately 1,86 g of EDTANa2in water and make up to 1 dm3. Standardize by titrating against standard magnesium sulfate solution (6.1).6.2.2 StandardizationPipette 10 cm3of the standard magnesium sulfate solution into a beaker (5.7). Add 200 cm3of water and adjust the pH to 10,3 by adding buffer solution

36、(6.4). Add about 0,1 g of Eriochrome Black T indicator (6.3) and titrate with the EDTANa2solution (6.2). The colour change is from red to permanent blue.1) Eriochrome is a registered trademark of Huntsman Petrochemical, LLC. Eriochrome Black T is an example of suitable product available commercially

37、. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the product named. 2 ISO 2017 All rights reservedBS ISO 11852:2017ISO 11852:2017(E)The concentration of the EDTANa2solution, c(EDTANa2), is given, in mol/dm3, by Formula (1):cV(

38、EDTANA),2=10 0 005(1)where V is the volume of EDTANa2solution used, in cm3.6.3 Eriochrome Black T indicator.Grind together, in a small pestle and mortar, 0,3 g of Eriochrome Black T and 100 g of sodium or potassium chloride to give a homogeneous mixture.6.4 Buffer solution.Dissolve 67,5 g of ammoniu

39、m chloride (NH4Cl) in 250 cm3of deionized water, mix with 570 cm3of 25 % ammonium hydroxide (NH4OH) and make up to 1 dm3with deionized water. The solution should have a pH of about 10,5.7 ProcedureCarry out the procedure in duplicate, using separate test portions obtained from the same homogenized s

40、ample. If the individual results differ from their mean by more than 0,05 percentage points when the results are expressed as a percentage or by more than 5 mg/kg when the results are expressed in mg/kg, repeat the determination.Fill each of two centrifuge tubes to 90 % of its capacity with field la

41、tex and place in the centrifuge. Balance the two tubes and centrifuge the latex for 3 min at between 2 500 m/s2(250g) and 5 000 m/s2(500g).Taking care not to disturb the sludge at the bottom of the tube, weigh approximately 2 g to 3 g of the supernatant latex into a beaker containing 100 cm3of water

42、. Mix well.Check the pH of the latex solution and, if it is less than 10,3, add sufficient buffer solution (6.4) to raise the pH above this value. Note that, if the ammonia concentration is less than 0,35 % with respect to the latex or less than 0,50 % with respect to the water content for a latex o

43、f 30 % dry-rubber content, it is not in fact necessary to adjust the pH in this way.Add about 0,1 g of Eriochrome Black T indicator (6.3) to the latex solution and stir. Then titrate with 0,005 mol/dm3EDTANa2solution (6.2) until the colour of the solution becomes blue.NOTE 1 The end-point is a littl

44、e difficult to detect with latex and it can be useful to have an over-titrated solution at hand for comparison.NOTE 2 This test method might not be applicable to field natural rubber latex containing preservatives other than ammonia, in particular, tetramethylthiuram disulfide (TMTD) or zinc oxide (

45、ZnO). ISO 2017 All rights reserved 3BS ISO 11852:2017ISO 11852:2017(E)8 Expression of resultsCalculate the magnesium content expressed as a percentage of the latex, wMg(%), using Formula (2):wcVmMg(%)2(EDTANa) 24,31=10(2)Calculate the magnesium content expressed in mg/kg of latex, wMg, using Formula

46、 (3):wcVmMg23(EDTANa) 24,31 10=(3)wherec(EDTANa2) is the concentration of the standardized EDTANa2solution used, in mol/dm3;V is the volume of EDTANa2solution used, in cm3;m is the mass of field latex taken, in g.Take as the test result the average of the two determinations: rounded to two decimal p

47、laces when the magnesium content is expressed as a percentage; rounded to the nearest whole number when the content is expressed in milligrams per kilogram.9 PrecisionSee Annex A.10 Test reportThe test report shall include the following information:a) a reference to this document, i.e. ISO 11852;b)

48、all details necessary for the complete identification of the product tested;c) the method of sampling used;d) the type of instrument used;e) the results obtained and the units in which they have been expressed;f) any unusual features noted during the determination;g) any operations not included in t

49、his document or in the International Standards to which reference is made, as well as any incident which might have affected the result;h) the date of the test.4 ISO 2017 All rights reservedBS ISO 11852:2017ISO 11852:2017(E)Annex A (informative) PrecisionA.1 The precision of the test method was 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 precision parameters should not be used for acceptanc