1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 12121:2012Chemicals used for treatmentof water intended for humanconsumption SodiumdisulfiteBS EN 12121:2012 BRITISH STANDARDNational forewordThis British Standard is the U
2、K implementation of EN 12121:2012. It supersedes BS EN 12121:2005 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee CII/59, Chemicals for drinking water treatment.A list of organizations represented on this committee can be obtained on request to its sec
3、retary.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 2013. Published by BSI Standards Limited 2013ISBN 978 0 580 77780 6 ICS 71.100.80 Compliance with a British Standard ca
4、nnot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2013.Amendments issued since publicationDate T e x t a f f e c t e dBS EN 12121:2012EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 1
5、2121 November 2012 ICS 71.100.80 Supersedes EN 12121:2005English Version Chemicals used for treatment of water intended for human consumption - Sodium disulfite Produits chimiques utiliss pour le traitement de leau destine la consommation humaine - Disulfite de sodiumProdukte zur Aufbereitung von Wa
6、sser fr den menschlichen Gebrauch - Natriumdisulfit This European Standard was approved by CEN on 23 September 2012. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without an
7、y alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other langua
8、ge made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark,
9、 Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR
10、 STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12121:2012: EBS EN 12121:2012EN 12121:2012 (E)
11、 2 Contents Page Foreword 3Introduction . 41 Scope 52 Normative references 53 Description . 54 Purity criteria 75 Test methods 86 Labelling Transportation Storage . 14Annex A (informative) General information on sodium disulfite 17Annex B (normative) General rules relating to safety . 18Bibliography
12、 19BS EN 12121:2012EN 12121:2012 (E) 3 Foreword This document (EN 12121:2012) has been prepared by Technical Committee CEN/TC 164 “Water supply”, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical
13、text or by endorsement, at the latest by May 2013, and conflicting national standards shall be withdrawn at the latest by May 2013. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible f
14、or identifying any or all such patent rights. This document supersedes EN 12121:2005. The significant technical differences between this edition and EN 12121:2005 are as follows: Modification of 6.2 on labelling, deletion of the reference to EU Directive 80/778/EEC of 15 July 1980 in order to take a
15、ccount of the latest Directive in force. According to the CEN/CENELEC Internal Regulations, the national standards organisations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yu
16、goslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 12121:2012EN 12121:2012 (E) 4 Introducti
17、on In respect of potential adverse effects on the quality of water intended for human consumption caused by the product covered by this European Standard: a) this European Standard provides no information as to whether the product may be used without restriction in any of the Member States of the EU
18、 or EFTA; b) it should be noted that, while awaiting the adoption of verifiable European criteria, existing national regulations concerning the use and/or the characteristics of this product remain in force. NOTE Conformity with this European Standard does not confer or imply acceptance or approval
19、of the product in any of the Member States of the EU or EFTA. The use of the product covered by this European Standard is subject to regulation or control by National Authorities. BS EN 12121:2012EN 12121:2012 (E) 5 1 Scope This European Standard is applicable to sodium disulfite used for treatment
20、of water intended for human consumption. It describes the characteristics of sodium disulfite and specifies the requirements and the corresponding test methods for sodium disulfite. It gives information on its use in water treatment. It also determines the rules relating to safe handling and use (se
21、e Annex B). 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (includi
22、ng any amendments) applies. EN ISO 3696, Water for analytical laboratory use Specification and test methods (ISO 3696) ISO 3165, Sampling of chemical products for industrial use Safety in sampling ISO 3629, Photography Processing chemicals Specifications for potassium metabisulfite ISO 5993, Sodium
23、hydroxide for industrial use Determination of mercury content Flameless atomic absorption spectrometric method ISO 6206, Chemical products for industrial use Sampling Vocabulary ISO 6353-1, Reagents for chemical analysis Part 1: General test methods ISO 8213, Chemical products for industrial use Sam
24、pling techniques Solid chemical products in the form of particles varying from powders to coarse lumps ISO 9297, Water quality Determination of chloride Silver nitrate titration with chromate indicator (Mohrs method) ISO 22743, Water quality Determination of sulfates Method by continuous flow analys
25、is (CFA) 3 Description 3.1 Identification 3.1.1 Chemical name Sodium disulfite. 3.1.2 Synonym or commons names Sodium metabisulfite, sodium pyrosulfite. 3.1.3 Relative molecular mass 190,10. 3.1.4 Empirical formula Na2S2O5. BS EN 12121:2012EN 12121:2012 (E) 6 3.1.5 Chemical formula Na2S2O5.3.1.6 CAS
26、-Registry Number 1)7681-57-4. 3.1.7 EINECS reference 2)231-673-0. 3.2 Commercial form The product is a crystalline powder.3.3 Physical properties 3.3.1 Appearance and odour The product is a white, free-flowing fine crystalline powder with a slight odour of sulfur dioxide. 3.3.2 Density The density o
27、f the product is 2,7 g/cm3at 20 C. The bulk density is approximately 1,3 g/cm3at 20 C. 3.3.3 Solubility (in water) The solubility of the product in water is 540 g/l at 20 C. 3.3.4 Vapour pressure Not applicable. 3.3.5 Boiling point at 100 kPa 3)Not applicable. 3.3.6 Crystallisation point The product
28、 decomposes above 150 C. 3.3.7 Specific heat Not known. 1) Chemical Abstracts Service Registry Number. 2)European Inventory of Existing Commercial Chemical Substances. 3)100 kPa = 1 bar. BS EN 12121:2012EN 12121:2012 (E) 7 3.3.8 Viscosity dynamic Not applicable. 3.3.9 Critical temperature Not applic
29、able. 3.3.10 Critical pressure Not applicable. 3.3.11 Physical hardness Not applicable. 3.4 Chemical properties The solution is weakly acid. The pH value of a saturated aqueous solution of sodium disulfite is between 4,5 and 5,0. Sodium disulfite dissolves in water forming sodium hydrogen sulfite. A
30、t elevated temperatures ( 150 C) or on contact with acids sulfur dioxide is generated. Sodium disulfite reacts violently with oxidising agents; e.g. with sodium hypochlorite or hydrogen peroxide. 4 Purity criteria 4.1 General This European Standard specifies the minimum purity requirements for sodiu
31、m disulfite used for the treatment of water intended for human consumption. Limits are given for impurities commonly present in the product. Depending on the raw material and the manufacturing process other impurities may be present and, if so, this shall be notified to the user and when necessary t
32、o relevant authorities. Users of this product should check the national regulations in order to clarify whether it is of appropriate purity for treatment of water intended for human consumption, taking into account raw water quality, required dosage, contents of other impurities and additives used i
33、n the products not stated in this product standard. Limits have been given for impurities and chemical parameters where these are likely to be present in significant quantities from the current production process and raw materials. If the production process or raw materials leads to significant quan
34、tities of impurities, by-products or additives being present, this shall be notified to the user. 4.2 Composition of commercial product The content of sodium disulfite shall not be less than a mass fraction of 95 % (Na2S2O5). The concentration of sodium disulfite shall be within 5 % of the manufactu
35、rers declared value. BS EN 12121:2012EN 12121:2012 (E) 8 4.3 Impurities and main by-products The sum of the content of sodium sulfate and sodium chloride shall not exceed a mass fraction of 5 % of the commercial product. 4.4 Chemical parameters The product shall conform to the requirements specified
36、 in Table 1. Table 1 Chemical parameters Parameter Limit mg/kg of commercial product Antimony (Sb) max 1 Arsenic (As) max 1 Cadmium (Cd) max 1 Chromium (Cr) max 1 Lead (Pb) max 5 Mercury (Hg) max 1 Nickel (Ni) max 1 Selenium (Se) max 1 NOTE Other chemical parameters and indicator parameters are not
37、relevant in sodium disulfite because the raw materials used in the manufacturing process are free of them. For parametric values of sodium disulfite on trace metal content in drinking water, see 1. 5 Test methods 5.1 Sampling Observe the general recommendations of ISO 3165 and take account of ISO 62
38、06. Prepare the laboratory sample(s) required by the relevant procedure described in ISO 8213. 5.2 Analyses 5.2.1 General All reagents shall be of a recognised analytical grade and the water used shall conform to the grade 3 specified in EN ISO 3696. 5.2.2 Main product 5.2.2.1 General The sodium dis
39、ulfite content shall be determined by the method for potassium disulfite described in ISO 3629. BS EN 12121:2012EN 12121:2012 (E) 9 5.2.2.2 Principle Sodium disulfite is oxidised with a fixed volume of iodine. The excess of added iodine is titrated with sodium thiosulfate. The determination includes
40、 other sulfites in addition to Na2S2O5, therefore the second titration, as described in ISO 3629, is omitted for the purpose of this determination. 5.2.2.3 Calculation The formula given in ISO 3629 for potassium disulfite has to be adapted for sodium disulfite. The sodium disulfite content CB1B, exp
41、ressed as a mass fraction in %, is given by the following formula: CB1= 4,76 ()()10032ccVm(1) where c2is the actual concentration, in moles per litre, of the sodium thiosulfate solution; c3is the actual concentration, in moles per litre, of the iodine solution; V is the volume, in millilitres, of th
42、e sodium thiosulfate solution used for the titration; m is the mass, in grams, of the test portion used for the titration; 4,76 is a conversion factor for the mass of sodium disulfite equivalent to 1 mole of iodine (i.e. 47,6) X the conversion factor for millilitres to litres (i.e. 0,001) X 100 (for
43、 percentage); 100 is the volume, in millilitres of iodine solution added for total oxidation. 5.2.3 Impurities 5.2.3.1 Sulfate The sulfate content shall be determined in accordance with ISO 22743. 5.2.3.2 Chloride The chloride content shall be determined in accordance with ISO 9297. 5.2.4 Chemical p
44、arameters 5.2.4.1 General The content of chemical parameters shall be determined using the procedures specified in Table 2. BS EN 12121:2012EN 12121:2012 (E) 10 Table 2 Procedures for the determination of chemical parameters Element Reference Method Wavelengthnm Flame As see 5.2.4.3 Hydride AAS 193,
45、7 n.a. Sb see 5.2.4.3 Hydride AAS 217,6 n.a.Cd ISO 6353-1 GM 29 See 5.2.4.2 AAS 228,8 air-acetylene Cr ISO 6353-1 GM 29 See 5.2.4.2 AAS 357,8 air-acetylenePb ISO 6353-1 GM 29 See 5.2.4.2 AAS 217,0 or 283,3 air-acetylene Ni ISO 6353-1 GM 29 See 5.2.4.2 AAS 232,0 oxidisingair-acetylene Se see 5.2.4.3
46、Hydride AAS 196,0 n.a. Hg in accordance with ISO 5993 flameless AAS 253,6 n.a. AAS = Atomic absorption spectrometry. n.a. = not applicable. 5.2.4.2 Determination of cadmium (Cd), chromium (Cr), lead (Pb) and nickel (Ni) 5.2.4.2.1 General The content of Cd, Cr, Pb and Ni shall be determined taking in
47、to account ISO 6353-1, modified as described in 5.2.4.2.2. 5.2.4.2.2 Procedure The elements Cd, Cr, Pb and Ni shall be determined using the standard addition method. The reference solutions shall be made by spiking the sample with standard solutions, which contain step-wise increasing contents of th
48、e elements to be determined. The amount of internal standard to be added can be estimated from a preliminary investigation, determining roughly the element content of the test sample from simple calibration. The steps in which internal standards are added shall be at least as high as the estimated c
49、ontent of the test sample. Carry out a blank determination by repeating the procedure using the same quantities of all reagents but omitting the test sample. 5.2.4.2.3 Expression of results Determine the correlation line by plotting the measured absorbencies of the spiked measurement solutions in relation to the element content. The spiked measurement solutions are produced by adding defined quantities of element to the measurement solution. They contain stepwise increasing contents of t
