1、BSI Standards PublicationBS ISO 17403:2014Rubber Determination ofmagnesium content of fieldand concentrated naturalrubber latices by titration(cyanide-free method)Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Not for ResaleNo reproduction or netwo
2、rking permitted without license from IHS-,-,-BS ISO 17403:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 17403:2014.The UK participation in its preparation was entrusted to TechnicalCommittee PRI/50, Rubber - Raw, natural and synthetic, includinglatex and
3、 carbon black.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2014. Published b
4、y BSI StandardsLimited 2014ISBN 978 0 580 77082 1ICS 83.040.10Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 28 February 2014.Amendments issued since publicationD
5、ate Text affectedCopyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014 ISO 2014Rubber Determination of magnesium content of field and concentrated natural
6、 rubber latices by titration (cyanide-free method)Caoutchouc Dtermination par titrage de la teneur en magnsium du latex de plantation et du latex concentr de caoutchouc naturel (mthode sans cyanure)INTERNATIONAL STANDARDISO17403First edition2014-03-01Reference numberISO 17403:2014(E)Copyright Britis
7、h Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014ISO 17403:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved. Unless othe
8、rwise 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 prior written permission. Permission can be requested from either ISO at the address
9、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 SwitzerlandCopyright British Standards Institution Provided by IHS under license with BSI - Unc
10、ontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014ISO 17403:2014(E) ISO 2014 All rights reserved iiiContents PageForeword iv1 Scope . 12 Normative references 13 Terms and definitions . 14 Apparatus . 15 Reagents 26 Method A Determinati
11、on of magnesium content of field latex . 26.1 Principle 26.2 Procedure 36.3 Number of determinations . 36.4 Calculation of results . 36.5 Expression of result 37 Method B Determination of magnesium content of concentrated latex 47.1 Principle 47.2 Procedure 47.3 Number of determinations . 47.4 Calcu
12、lation of results . 57.5 Expression of result 58 Test report . 5Annex A (informative) Precision . 7Bibliography .10Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS
13、ISO 17403:2014ISO 17403:2014(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. Each member body interes
14、ted 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 International Electrotechnical C
15、ommission (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 types of ISO document
16、s 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 not be held responsible f
17、or 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 information given for the
18、convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Fore
19、word - Supplementary information.The committee responsible for this document is ISO/TC 45, Rubber and rubber products, Subcommittee SC 3, Raw material (including latex) for use in the rubber industry.iv ISO 2014 All rights reservedCopyright British Standards Institution Provided by IHS under license
20、 with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014INTERNATIONAL STANDARD ISO 17403:2014(E)Rubber Determination of magnesium content of field and concentrated natural rubber latices by titration (cyanide-free method)1 Sco
21、peThis International Standard specifies a cyanide-free titration method for the determination of the magnesium content in field and concentrated natural rubber latex.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable
22、for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 124, Latex, rubber Determination of total solids contentISO 648, Laboratory glassware Single-volume pipettes3 Terms
23、and definitionsFor the purposes of this document, the following terms and definitions apply.3.1natural rubber latex concentratenatural rubber latex from Hevea brasiliensis containing ammonia and/or other preservatives, which has been subjected to some process of concentration3.2field natural rubber
24、latexnatural rubber latex with or without a preservative and prior to concentration or any other processingNote 1 to entry: The preservative is added to maintain the original state of the latex as it came from the tree.3.3magnesium contentcontent of magnesium equivalent to alkaline-earth metals, mai
25、nly magnesium and calcium, present in all soluble forms that may be titrated with ethylenediaminetetraacetic acid in field or concentrated natural rubber latex4 Apparatus4.1 Burette, 50 cm3graduated.4.2 Analytical balance, accurate to 0,1 mg.4.3 Volumetric pipettes, of capacities 2 cm3, 5 cm3and 10
26、cm3complying with the requirements of ISO 648, class A. ISO 2014 All rights reserved 1Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014ISO 17403:2014(
27、E)5 ReagentsUse reagents of recognized analytical quality. And, wherever water is specified, use distilled water or water of equivalent purity.5.1 Magnesium sulfate solution.Dissolve 1,232 4 g magnesium sulfate heptahydrate (MgSO47H2O) in water and make up to 1 dm3in a flask. 1 cm3of this solution c
28、ontains magnesium which is equivalent to 1 cm3of 0,005 mol/dm3EDTA.5.2 EDTA solution, 0,005 mol/dm3.Dissolve approximately 1,86 g of sodium salt of ethylenediaminetetraacetic acid (EDTA) in water and make up to 1 dm3. Standardize against the standard solution of magnesium sulfate specified in 5.1.5.
29、3 Masking agent solution.Dissolve sufficient sodium hydrogen sulphide hydrate (NaHSxH2O) to give at least 1,68 g sodium hydrogen sulfide (NaHS). Transfer into a 100 cm3volumetric flask and make up to volume with water. 1 cm3of this solution is equivalent to 1 cm3of 0,3 mol/dm3NaHS.NOTE If the number
30、 of hydrate groups is not indicated (xH2O), NaHS content may be calculated from the percentage of NaHS assay in the specification data. For example, if the percentage of NaHS assay equals 60,0 %, 2,80 g of NaHSxH2O is necessary to give 1,68 g of NaHS.5.4 Eriochrome black T indicator.Grind together,
31、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.5.5 Buffer solution of ammonium chloride/ammonium hydroxide.Dissolve 67,5 g of ammonium chloride (NH4Cl) in 250 cm3of deionized water, mix with 570 cm3of 25 % ammonium hy
32、droxide (NH4OH) and make up to 1 dm3with deionized water. The solution should have a pH of about 10,5.5.6 Standardization of EDTA.Pipette 10 cm3of the standard magnesium sulfate solution into a beaker. Add 200 cm3of water and adjust the pH to 10,3 by adding 6 cm3of the buffer solution. Add 0,1 g of
33、Eriochrome black T indicator and titrate with EDTA solution.5.7 Calcium hydroxide powder.6 Method A Determination of magnesium content of field latex6.1 PrincipleThis method determines the soluble concentration of divalent alkaline earth ions present in the latex after the dilution. The results are
34、expressed as magnesium content on the assumption that other divalent alkaline earth ions, such as calcium, are only present at the micromolar concentration level.The latex is diluted with water. The soluble magnesium content in the latex is determined by titration with the sodium salt of EDTA in the
35、 presence of NH4Cl/NH4OH buffer using sulfide releasing agent as masking agent and Eriochrome Black T as indicator.The magnesium content is expressed as a percentage of the total solids content of latex.2 ISO 2014 All rights reservedCopyright British Standards Institution Provided by IHS under licen
36、se with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014ISO 17403:2014(E)6.2 ProcedureWeigh approximately 2,0 g of the field latex into a conical flask and dilute to 100 cm3with water.Add 2,0 cm3of ammonium chloride/ammonium
37、 hydroxide buffer solution to keep the pH of latex solution between 10,0 and 10,5.Then add 1,0 cm3of 0,3 mol/dm3NaHS to the latex solution, mix well and leave the solution for at least 10 s.Add 0,1 g of Eriochrome black T indicator to the latex solution and mix well.Then titrate with the standard 0,
38、005 mol/dm3EDTA solution until the colour of the solution loses the last trace of red and becomes pure blue.At the end of titration, add approximately 0,5 g of calcium hydroxide into the mixture, shake well and leave for at least 1 min before disposing.NOTE If the pH value of the solution is higher
39、than 11 after adding 2,0 cm3of ammonium chloride/ammonium hydroxide buffer solution, the volume of buffer could be reduced in order to keep pH value in the range of 10,0 to 10,5.6.3 Number of determinationsCarry out the procedure in duplicate, using separate test portions obtained from the same batc
40、h of homogenized sample.6.4 Calculation of resultsCalculate the magnesium content expressed as a percentage of the latex or a percentage of the total solid content using the following formula:MgMVWlatexEDTA EDTA24,31 1001 000=orMgMVWTSCTSCEDTA EDTA24,31 100001000=whereMglatexis the magnesium content
41、 expressed as a percentage of the latex, in percent (%);MgTSCis the magnesium content expressed as a percentage of the total solid content, in per-cent (%);MEDTAis the concentration of EDTA solution used, in moles per cubic decimetre (mol/dm3);VEDTAis the volume of EDTA solution used, in cubic centi
42、metres (cm3);W is the mass, of field latex taken, in grams (g);TSC is the total solid content of field latex, expressed in percent (%).6.5 Expression of resultThe test result is the average of two determinations, rounded to two decimal places when the magnesium concentration is expressed as a percen
43、tage. ISO 2014 All rights reserved 3Copyright British Standards Institution Provided by IHS under license with BSI - Uncontrolled Copy Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-BS ISO 17403:2014ISO 17403:2014(E)7 Method B Determination of magnesium content of
44、 concentrated latex7.1 PrincipleSerum from concentrated latex is prepared by diluting 10 g of concentrated latex in 10 cm3water, before coagulating with acetic acid. A certain portion of serum is then buffered to pH in the range of 10,0 to 10,5. Then masking agent, NaHS, and Eriochrome black T indic
45、ator are added before titration with ethylenediaminetetraacetic acid.7.2 Procedure7.2.1 Test portionTake a portion of thoroughly mixed concentrated latex containing about 10,0 g of total solids. Determine the total solid content (TSC) of concentrated latex according to ISO 124.7.2.2 Preparation of t
46、est solutionDilute 10,0 g of concentrated latex sample with 10,0 cm3water and coagulate with 5,0 cm3of 25 % acetic acid solution until clear serum is obtained.Pipette 10,0 cm3of serum into a conical flask and add 4,0 cm3of ammonium chloride/ammonium hydroxide buffer solution pH 10,5 to raise the pH
47、to the range of 10,0 to 10,5.Add 1,0 cm3of masking agent solution, 0,3 mol/dm3NaHS, to the latex solution and mix well for at least 10 s. Add 0,1 g of Eriochrome black T indicator to the latex solution and mix well.Titrate the residual magnesium content present in the resultant serum with the sodium
48、 salt of ethylenediaminetetraacetic acid (EDTA) in the presence of a buffer using Eriochrome Black T as indicator.At the end of titration, add approximately 0,5 g of calcium hydroxide into the mixture, shake well and leave for at least 1 min before disposing.NOTE If the pH value of solution is higher than 11 after adding 4,0 cm3of ammonium chloride/ammonium hydroxide buffer solution, the volume of buffer could be reduced in order to keep pH value in the range of 10,0 to 10,5. The end-point is a little difficult to detect with latex and it is advisable to have an over-
