1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 12125:2012Chemicals used for treatmentof water intended for humanconsumption SodiumthiosulfateBS EN 12125:2012 BRITISH STANDARDNational forewordThis British Standard is the
2、 UK implementation of EN 12125:2012. Itsupersedes BS EN 12125:2005 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee CII/59, Chemicals for drinking water treatment.A list of organizations represented on this committee can beobtained on request to its secr
3、etary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 77785 1ICS 13.060.20; 71.100.80Compliance with a British Standa
4、rd cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 January 2013.Amendments issued since publicationDate Text affectedBS EN 12125:2012EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12125 Nov
5、ember 2012 ICS 71.100.80 Supersedes EN 12125:2005English Version Chemicals used for treatment of water intended for human consumption - Sodium thiosulfate Produits chimiques utiliss pour le traitement de leau destine la consommation humaine - Thiosulfate de sodium Produkte zur Aufbereitung von Wasse
6、r fr den menschlichen Gebrauch - Natriumthiosulfat 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
7、 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 languag
8、e 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 12125:2012: EBS EN 12125:2012EN 12125:2012 (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 thiosulfate . 15Bibliography . 17BS EN 12125:2012EN 12125:2012 (E) 3 Foreword This d
12、ocument (EN 12125:2012) 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
13、 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 doc
14、ument supersedes EN 12125:2005. The significant technical differences between this edition and EN 12125:2005 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
15、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,
16、 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 12125:2012EN 12125:2012 (E) 4 Introduction In respect of potential adverse effects on the qual
17、ity 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 t
18、he 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 o
19、r EFTA. The use of the product covered by this European Standard is subject to regulation or control by National Authorities. BS EN 12125:2012EN 12125:2012 (E) 5 1 Scope This European Standard is applicable to sodium thiosulfate used for treatment of water intended for human consumption. It describe
20、s the characteristics and specifies the requirements of sodium thiosulfate and refers to the corresponding analytical methods. It gives information for its use in water treatment. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are
21、 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, Sam
22、pling of chemical products for industrial use Safety in sampling 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 analys
23、is 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 10636, Photography Processing chemicals Specifications for anhydrous sodium thiosulfate and sodium thiosulfate
24、pentahydrate ISO 22743, Water quality Determination of sulfates Method by continuous flow analysis (CFA) 3 Description 3.1 Identification 3.1.1 Chemical name Sodium thiosulfate. 3.1.2 Synonym or commons names Sodium thiosulfate, sodium hyposulfite. 3.1.3 Relative molecular mass 158,11 (anhydrous). 3
25、.1.4 Empirical formula Na2S2O3. BS EN 12125:2012EN 12125:2012 (E) 6 3.1.5 Chemical formula Na2S2O3. 3.1.6 CAS-Registry Number 1)7772-98-7 (anhydrous); 10102-17-7 (pentahydrate). 3.1.7 EINECS reference 2)231-867-5. 3.2 Commercial form The product is a crystalline powder. 3.3 Physical properties 3.3.1
26、 Appearance The hydrated product is colourless crystal. The anhydrous product is a white powder. 3.3.2 Density The particle density of the hydrated product is 1,69 g/cm3to 1,73 g/cm3at 20 C. 3.3.3 Solubility in water The solubility of the product in water is 700 g/l at 20 C (anhydrous); for pentahyd
27、rate : 2910 g/l at 45 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 starts to decompose at 45 C to 50 C. 3.3.7 Specific heat Not known. 1) Chemical Abstracts Service Registry Number. 2) European Inventory of Existing
28、 Commercial Chemical Substances. 3) 100 kPa = 1 bar. BS EN 12125:2012EN 12125:2012 (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 pH value of a dil
29、uted aqueous solution of sodium thiosulfate is approximately neutral (6,5 to 8). Sodium thiosulfate dissolves silver halogenids and other silver salts. At elevated temperatures ( 50 C), sulfur dioxide is generated. Sodium thiosulfate releases sulfur dioxide when mixed with acids. Sodium thiosulfate
30、reacts violently with oxidising agents; e.g. with sodium hypochlorite or hydrogen peroxide. It shall not come into contact with acids, iodine, lead and silver salts. 4 Purity criteria 4.1 General This European Standard specifies the minimum purity requirements for sodium thiosulfate used for the tre
31、atment 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. User
32、s 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 product not stated in
33、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-prod
34、ucts or additives being present, this shall be notified to the user. 4.2 Composition of commercial product The concentration of sodium thiosulfate anhydrous shall not be less than a mass fraction of 95 % of Na2S2O3. The concentration of sodium thiosulfate pentahydrate shall not be less than a mass f
35、raction of 95% of Na2S2O3.5 H2O. BS EN 12125:2012EN 12125:2012 (E) 8 4.3 Impurities and main by-products The content of sodium sulfate shall not exceed a mass fraction of 5 % . 4.4 Chemical parameters The product shall conform to the requirements specified in Table 1. Table 1 Chemical parameters Par
36、ameter Limitmg/kg of commercial product Antimony (Sb) max 2 Arsenic (As) max 0,5 Cadmium (Cd) max 0,1 Chromium (Cr) max 5 Lead (Pb) max 5 Mercury (Hg) max 0,1 Nickel (Ni) max 5 Selenium (Se) max 2 NOTE Pesticides and polycyclic aromatic hydrocarbons and cyanides (CN ) are not relevant in sodium thio
37、sulfate because the raw materials used in the manufacturing are free of them. For parametric values of sodium thiosulfate 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
38、sample(s) required by the relevant procedure described in ISO 8213. 5.2 Analyses 5.2.1 Main product The sodium thiosulfate content shall be determined in accordance with ISO 10636. 5.2.2 Impurities 5.2.2.1 Sulfate The content of sodium sulfate (Na2SO4) shall be determined in accordance with ISO 2274
39、3. BS EN 12125:2012EN 12125:2012 (E) 9 5.2.3 Chemical parameters 5.2.3.1 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
40、.3.3 Hydride AAS 193,7 n.a.Sb see 5.2.3.3 Hydride AAS 217,6 n.a. Cd ISO 6353-1 GM 29see 5.2.3.2 AAS 228,8 air-acetylene Cr ISO 6353-1 GM 29see 5.2.3.2 AAS 357,8 air-acetylene Pb ISO 6353-1 GM 29see 5.2.3.2 AAS 217,0 or 283,3 air-acetylene Ni ISO 6353-1 GM 29see 5.2.3.2 AAS 232,0 oxidising acetylene-
41、air Se see 5.2.3.3 Hydride AAS 196,0 n.a.Hg in accordance withISO 5993 flameless AAS 253,6 n.a. AAS = Atomic Absorption Spectroscopy. n.a. = not applicable. 5.2.3.2 Determination of cadmium (Cd), chromium (Cr), lead (Pb) and nickel (Ni) 5.2.3.2.1 Principle The elements cadmium (Cd), chromium (Cr), l
42、ead (Pb) and nickel (Ni) are determined using atomic absorption spectrometry with the standard additions technique. 5.2.3.2.2 Reagents All reagents shall be of a recognised analytical grade and the water used shall conform to the grade 3 specified in EN ISO 3696. 5.2.3.2.2.1 Standard solution (100 g
43、/l Cd, Cr ,Pb or Ni) The standard solution shall be freshly prepared on the day of use by individual dilution of a stock solution. This stock solution with a Cd, Cr, Pb or Ni content of at least 1 mg/l shall be made by dilution of standard solutions of Cd, Cr, Pb and Ni which are available from all
44、major suppliers of laboratory chemicals. This stock solution shall be kept in containers of tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE) or polyethylene (PE). BS EN 12125:2012EN 12125:2012 (E) 10 The stock solution should not be kept for longer than four we
45、eks. 5.2.3.2.3 Apparatus Ordinary laboratory apparatus and the following: 5.2.3.2.3.1 Atomic absorption spectrometer with the measurement parameters specified in Table 2. 5.2.3.2.4 Procedure 5.2.3.2.4.1 Test portion Weigh 1 g (m) to the nearest 0,01 mg of the laboratory sample into a 100 ml one-mark
46、 volumetric flask and make up to the mark at 20 C with water. 5.2.3.2.4.2 Determination The reference solutions shall be made by spiking the sample with the standard solutions, which contain stepwise increasing contents of the elements to be determined. NOTE The amount of internal standard to be add
47、ed 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 have to be added shall be at least as high as the estimated content of the test sample. With the spectrometer (5.2.3.2.3.1),
48、 carry out the measurement with the parameters specified in Table 3 in accordance with the manufacturers instructions. Repeat the procedure with all reagents and the same volume of standard solution to be added using water in place of the sample as a blank determination. 5.2.3.2.5 Expression of resu
49、lts Prepare a calibration curve using the measured absorbencies of the spiked measurement solutions. Read the concentration of each element in the test solution by extrapolation of the correlation line to absorbance A = 0 (see Figure 1). Similarly determine the element concentration of the blank solution (see Figure 2) and subtract from the result obtained for the test solution. Alternatively, the evaluation can be carried out by linear regression. Additional dilution steps shall be compensated i
