SIST EN 12121:2013

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kemikalije, ki se uporabljajo za pripravo pitne vode - Natrijev disulfitProdukte zur Aufbereitung von Wasser für den menschlichen Gebrauch - NatriumdisulfitProduits chimiques utilisés pour le traitement de l'eau destinée à la consommation humaine - Disulfite de sodiumChemicals used for treatment of water intended for human consumption - Sodium disulfite71.100.80Chemicals for purification of water13.060.20Pitna vodaDrinking waterICS:Ta slovenski standard je istoveten z:EN 12121:2012SIST EN 12121:2013en,fr,de01-april-2013SIST EN 12121:2013SLOVENSKI
STANDARDSIST EN 12121:20051DGRPHãþD



SIST EN 12121:2013



EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 12121
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 utilisés pour le traitement de l'eau destinée à la consommation humaine - Disulfite de sodium Produkte zur Aufbereitung von Wasser für 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 any 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 language 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, 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 STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR 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: ESIST EN 12121:2013



EN 12121:2012 (E) 2 Contents Page Foreword . 3Introduction . 41Scope . 52Normative references . 53Description . 54Purity criteria . 75Test methods . 86Labelling — Transportation — Storage . 14Annex A (informative)
General information on sodium disulfite . 17Annex B (normative)
General rules relating to safety . 18Bibliography . 19 SIST EN 12121:2013



EN 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 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 for 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 account 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 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 the United Kingdom.
SIST EN 12121:2013



EN 12121:2012 (E) 4 Introduction 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 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 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.
SIST EN 12121:2013



EN 12121:2012 (E) 5 1 Scope This European Standard is applicable to sodium disulfite used for treatment 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 (see 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 (including 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 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 — Sampling 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 (Mohr's method) ISO 22743, Water quality — Determination of sulfates — Method by continuous flow analysis (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. SIST EN 12121:2013



EN 12121:2012 (E) 6 3.1.5 Chemical formula Na2S2O5. 3.1.6 CAS-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 of the product is 2,7 g/cm3 at 20 °C. The bulk density is approximately 1,3 g/cm3 at 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 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. SIST EN 12121:2013



EN 12121:2012 (E) 7 3.3.8 Viscosity dynamic Not applicable. 3.3.9 Critical temperature Not applicable. 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. At 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 sodium 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 to 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 in 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 quantities 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 manufacturer's declared value. SIST EN 12121:2013



EN 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 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 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 6206. 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 disulfite content shall be determined by the method for potassium disulfite described in ISO 3629.
SIST EN 12121:2013



EN 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 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 I
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