EN 12121:2005

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Kemikalije, ki se uporabljajo za pripravo pitne vode - Natrijev disulfitProdukt zue Aufbereitung von Wasser den menschlichen Gebrauch - NatriumdisulfitProduits chimiques utilisés pour le traitement de l'eau destinée a 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 12121:2005SIST EN 12121:2005en01-september-2005SIST EN 12121:2005SLOVENSKI
STANDARDSIST EN 12121:20001DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 12121
June 2005 ICS 71.100.80
Supersedes EN 12121:1998
English 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 Produkt zue Aufbereitung von Wasser den menschlichen Gebrauch - Natriumdisulfit This European Standard was approved by CEN on 12 May 2005.
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 Central Secretariat 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 Central Secretariat has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36
B-1050 Brussels © 2005 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12121:2005: ESIST EN 12121:2005

General information on sodium disulfite.16 Annex B (normative)
General rules relating to safety.17 Bibliography.18
: 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.
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 12121:2005

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 oxidizing 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. NOTE 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. 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. SIST EN 12121:2005

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 recognized analytical grade and the water used shall conform to 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.
5.2.2.3 Calculation The equation given in ISO 3629 for potassium disulfite has to be adapted for sodium disulfite. The sodium disulfite content C1, expressed as a mass fraction in %, is given by the following equation: C1 = 4,76 ()()()10032×−×ccVm (1)
where: c2 is the actual concentration, in moles per litre, of the sodium thiosulfate solution;
c3 is the actual concentration, in moles per litre, of the iodine solution;
V is the volume, in millilitres, of the 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 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. SIST EN 12121:2005

5.2.4 Chemical parameters 5.2.4.1 General The content of chemical parameters shall be determined using the procedures specified in Table 2. Table 2 — Procedures for the determination of chemical parameters Element Reference Method Wavelength nm Flame As see 5.2.4.3 Hydride AAS 193,7 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-acetylene Pb 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 oxidizing air-acetylene Se see 5.2.4.3 Hydride AAS 196,0 n.a. Hg in accordance
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