12946 fm BRITISH STANDARD BS EN 12946 2000 Incorporating Corrigendum No 1 Liming materials — Determination of calcium content and magnesium content — Complexometric method The European Standard EN 129[.]
BRITISH STANDARD BS EN 12946:2000 Incorporating Corrigendum No Liming materials — Determination of calcium content and magnesium content — Complexometric method The European Standard EN 12946:1999 has the status of a British Standard ICS 65.080 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 12946:2000 National foreword This British Standard is the official English language version of EN 12946:1999, including Corrigendum February 2002 The UK participation in its preparation was entrusted to Technical Committee CII/37, Fertilizers and related chemicals, which has the responsibility to: — aid enquirers to understand the text; — present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; — monitor related international and European developments and promulgate them in the UK A list of organizations represented on this committee can be obtained on request to its secretary The United Kingdom did not support this standard at the CEN Enquiry stage and voted against its acceptance at the Formal Vote stage The principal UK objections were as follows a) The technique described is unsuitable for a standard reference method because the end-points are difficult to detect and only highly skilled analysts with regular practice can carry out the determination b) The method has very limited applicability c) A more suitable technique for determination of calcium content, the calcium oxalate titrimetric method is described in prEN 13475 (currently in course of preparation) while the determination of magnesium content is covered by the method described in EN 12947 d) The precision data quoted for this method is incomplete and highly suspect Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages to and a back cover The BSI copyright notice displayed in this document indicates when the document was last issued This British Standard, having been prepared under the direction of the Sector Committee for Materials and Chemicals, was published under the authority of the Standards Committee and comes into effect on 15 April 2000 © BSI July 2002 ISBN 580 35922 Amendments issued since publication Amd No Date Comments 13810 corrigendum July 2002 Addition to clause EUROPEAN STANDARD EN 12946 NORME EUROPÉENNE EUROPÄISCHE NORM January 2000 ICS 65.080 Incorporating corrigendum February 2002 English version Liming materials — Determination of calcium content and magnesium content — Complexometric method Amendements calciques et/ou magnésiens — Détermination de la teneur en calcium et de la teneur en magnésium — Méthode par complexométrie Calcium-Magnesium-Bodenverbesserungsmittel — Bestimmung des Calcium- und Magnesiumgehaltes — Komplexometrisches Verfahren This European Standard was approved by CEN on 13 November 1999 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, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 2000 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 12946:2000 E EN 12946:2000 Foreword This European Standard has been prepared by Technical Committee CEN/TC 260, Fertilizers and liming materials, 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 July 2000, and conflicting national standards shall be withdrawn at the latest by July 2000 According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, lreland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom Contents Foreword Scope Normative references Principle Reagents Apparatus Sampling Procedure Expression of results Precision 10 Test report Bibliography Page 3 3 5 6 © BSI July 2002 EN 12946:2000 Scope This European Standard specifies a complexometric method for the determination of the calcium content and the magnesium content of liming materials It is not applicable to products with a mass fraction less than % (m/m) magnesium or those with a mass fraction more than % P2O5 and is not applicable to silicate liming materials Normative references This European Standard incorporates, by dated or-undated-reference provisions from other publications These normative references are cited at the appropriate places in the text and the publications are listed hereafter For dated references, subsequent amendments to or revisions of these publications apply to this European Standard only when incorporated in it by amendment or revision For undated references the latest edition of the publication referred to applies EN 459-2, Building lime — Part 2: Test methods EN 1482, Sampling of solid fertilizers and liming materials ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth Principle A test portion is extracted with boiling hydrochloric acid solution After filtration and dilution, an aliquot portion is titrated against EDTA solution with calcein/thymolphthalein or calcon carbonic acid as an indicator in order to measure calcium A second aliquot portion is titrated against EDTA solution with eriochrome black T as indicator in order to measure calcium and magnesium Reagents 4.1 General In principle, commercially available standard solutions may be used instead of standard solutions produced on-site in the laboratory Variations in concentration shall be taken into account for the calculation of the results 4.2 Hydrochloric acid solution @20 = 1,09 g/ml Add part by volume of hydrochloric acid (@20 = 1,18 g/ml) to part by volume of water 4.3 Hydrochloric acid solution c(HCI) = mol/l approximately 4.4 Hydrochloric acid solution c(HCI) = 0,5 mol/l approximately 4.5 Standard calcium solution, containing 2,004 g of calcium per litre Weigh 5,004 g of dry calcium carbonate into a 500 ml beaker and add 100 ml of water Under continuous stirring, slowly add 120 ml of hydrochloric acid solution (4.3) Drive off the carbon dioxide by boiling, cool and transfer the solution quantitatively into a 000 ml volumetric flask and dilute to the mark with water Check the standard strength of the solution by titration with the EDTA standard solution (4.7) according to 7.3 ml of this solution should contain 2,004 mg of Ca (2,804 mg of CaO) and should correspond to ml of the EDTA standard solution (4.7) 4.6 Standard magnesium solution, containing 1,216 g of magnesium per litre 4.6.1 Weigh 1,232 g of magnesium sulfate (MgSO4·7H20) into a 100 ml volumetric flask, dissolve in hydrochloric acid solution (4.4) and dilute to the mark with the same solution or © BSI July 2002 EN 12946:2000 4.6.2 Calcined magnesium oxide (MgO) at 600 °C for h Weigh 2,016 g of the freshly calcined MgO into a 500 ml beaker, dissolve in 100 ml of water and 120 ml of hydrochloric acid solution (4.3) Transfer the solution into a 000 ml volumetric flask and dilute to the mark with water ml of this solution should contain 1,216 mg Mg (2,016 mg of MgO/ml) Before use check the Mg content of each standard solution after preparation 4.7 Ethylenediamine tetraacetic acid (EDTA) standard solution, c(EDTA) = 0,05 mol/l Weigh 18,61 g of ethylenediamine tetraacetic acid dihydrate disodium salt (EDTA; C1OH14N2Na2O8·2H2O) into a 000 ml volumetric flask and dilute to the mark with water Check the standard strength of the solution by titration of 20 ml of the standard solution 4.6 according to 7.2.2 ml of the EDTA standard solution should correspond to 1,216 mg of Mg or 2,016 mg of MgO and to 2,004 mg of Ca or 2,804 mg of CaO NOTE The stoichiometric EDTA/metal ion-ration is always 1:1 whatever the valency of the determination metal ionis 4.8 Calcein thymolphthalein indicator Carefully mix 0,2 g of calcein with 0,12 g thymolphthalein and 20 g of potassium nitrate in a mortar Use 10 mg of this mixture for each titration The indicator changes from green to orange Titration shall be carried out until an orange is obtained which is free from green tinges 4.9 Calcon carbonic acid indicator Dissolve 400 mg of calcon carbonic acid in 100 ml of methanol This solution should only be kept for approximately four weeks Use three drops of this solution The indicator changes its colour from red to blue Titration shall be carried out until a blue colour is obtained which is free from red tinges 4.10 Eriochrome black T indicator Dissolve 300 mg of eriochrome black T in a mixture of 25 ml of propan-1-ol and 15 ml of triethanolamine This solution may only be kept for approximately four weeks Use three drops of this solution This indicator changes its colour from red to blue and titration shall be carried out until a blue colour is obtained which is free from red tinges It changes colour only when magnesium is present If necessary add ml of the standard solution (4.6) 4.11 Triethanolamine Aqueus solution of triethanolamine with a mass fraction of 50 % 4.12 Buffer solution, pH 10,5 Dissolve 33 g of ammonium chloride in 100 ml of water in a 500 ml volumetric flask, add 250 ml of concentrated ammonia solution (@20 = 0,92 g/ml; about 25 % (m/m) NH3 solution) and dilute to the mark with water 4.13 Sodium hydroxide solution c(NaOH) = mol/l Apparatus Usual laboratory apparatus and in particular the following: 5.1 Test sieve, conforming to the requirements of ISO 3310-1, of nominal aperture size 250 4m 5.2 Pestle and mortar, each of porcelain, or mechanical grinder 5.3 Electric hot plate, with adjustable temperature 5.4 Magnetic or mechanical stirrer 5.5 pH meter, minimum sensitivity 0,05 units with suitable electrodes, calibrated using two suitable buffer solutions © BSI July 2002 EN 12946:2000 Sampling Sample the liming materials in accordance with EN 1482 Procedure 7.1 Preparation 7.1.1 Preparation of test sample Prepare the received laboratory sample by grinding (5.2) and sieving it rapidly through the test sieve (5.1) Grind the sample to pass the 250 4m sieve Mix the test sample thoroughly 7.1.2 Preparation of test solution Weigh about g to the nearest 0,001 g of the test sample into a 600 ml beaker and add approximately 400 ml of water Carefully add 50 ml of hydrochloric acid solution (4.2) and boil for 30 Allow to cool to ambient temperature under stirring Transfer the solution quantitatively to a 500 ml volumetric flask, dilute to the mark with water and mix Filter through a dry filter, discarding the first 50 ml of the filtrate The solution shall be clear without any turbidity Store this test solution in a stoppered flask, if the determination is not carried out immediately afterwards 7.2 Determination 7.2.1 Aliquot portion Take an aliquot portion, expected to contain between 15 mg and 30 mg of calcium and between mg and 18 mg of magnesium of the test solution (7.1.2) 7.2.2 Titration in the presence of eriochrome black T Pipette the aliquot portion (7.2.1) into a 400 ml beaker Neutralize the surplus acid with the sodium hydroxide solution (4.13) using the pH meter Dilute with water to approximately 100 ml Add ml of the buffer solution (4.12) The pH should be 10,5 ± 0,1 Add ml Triethanolamine (4.11) and three drops of the eriochrome black T indicator (4.10) Stir gently with the stirrer (5.4) and titrate with the EDTA standard solution (4.7) NOTE The use of triethanolamine is not required for products with a low content of impurities (e.g iron) NOTE In particular the eriochrome black T indicator and the calcon carbonic acid indicator are often sensitive to oxidation by air Therefore, the solution may lose colour during titration Add one or two drops of the corresponding indicator solution if this occurs NOTE In particular the eriochrome T-magnesium complex is often relatively stable Therefore, it may take some time for the change in colour at the final point of titration For that reason it is important to operate the titration very carefully It may be useful to check the final point of titration with a drop of standard magnesium solution (4.6) or standard calcium solution (4.5) NOTE Observe the colour of the solution from horizontal position at the end of the titration Place the beaker with the titration solution well lit in front of a white coloured background The observation of the change in colour may also be facilitated by placing the beaker on frosted glass lighted moderately from below (e.g with a 25 W lamp) 7.2.3 Titration in the presence of calcein thymolphthalein or calcon carbonic acid Pipette the aliquot portion (7.2.1) into a 400 ml beaker Neutralize the surplus acid with the sodium hydroxide solution (4.13) using the pH meter and adjust the pH value to 13,0 The pH value shall not fall below this value during titration Dilute with water to about 100 ml Add ml Triethanolamine (4.11) and the indicator (4.8) or (4.9) Stir gently with the stirrer (5.4) and titrate with the EDTA standard solution (4.7) (see notes to in 7.2.2) 7.3 Control test of the standard solutions Carry out a determination on aliquot parts of solutions (4.5 and 4.6) such that the Ca/Mg ratio is approximately equal to that of the test solution to be anaiyzed For this test take (a) ml of the standard calcium solution (4.5) and (b-a) ml of the standard magnesium solution (4.6), where (a) and (b) are the volumes (in millilitres) of EDTA solution used in the two titrations of the test solution described in 7.2.3 and 7.2.2 respectively © BSI July 2002 EN 12946:2000 This procedure is correct only if the standard solutions of EDTA, calcium and magnesium are exactly equivalent If this is not the case, it is necessary to make the appropriate corrections Expression of results The calcium content wCa and the magnesium content wMg, expressed as a percentage by mass, is given by the following equations: V1 ´ T1 wCa = m (1) ( V – V1 ) ´ T wMg = m where m is the mass of sample contained in the aliquot portion (7.2.1) in grams; V1 is the volume of EDTA standard solution used for the titration in the presence of calcein/thymolphthalein or calcon carbonic acid in millilitres; V2 is the volume of EDTA standard solution used for the titration in the presence of eriochrome black T in millilitres; T1Ca 0,2004 x correction factor Kc(EDTA) of the EDTA standard solution in grams per litre (according to 4.7); T2Mg 0,1216 x correction factor Kc(EDTA) of the EDTA standard solution in grams per litre (according to 4.7) To calculate the calcium content expressed as CaO and the magnesium content expressed as MgO use the following factors: T1CaO 0,2804 x correction factor Kc(EDTA) of the EDTA standard solution in grams per litre (according to 4.7); T2MgO 0,2016 x correction factor Kc(EDTA) of the EDTA standard solution in grams per litre (according to 4.7) (2) Precision 9.1 General The values derived from inter-laboratory tests with building lime products in accordance with EN 459-2 9.2 Repeatability The absolute difference between two single test results found on identical test material by one operator using the same apparatus within the shortest feasible time interval will exceed the repeatability limit r in not more than % of cases The values are: sr = 0,15 % (m/m) for Ca; and sr = 0,21 % (m/m) for Mg NOTE sr is the repeatability standard deviation 9.3 Reproducibility The absolute difference between two single test results on identical test material reported by two laboratories will exceed the reproducibility limit R in not more than % of the cases The values are: sR = 0,43 % (m/m) for Ca; and sR 0,25 % (m/m) for Mg NOTE sR is the reproducibility standard deviation © BSI July 2002 EN 12946:2000 10 Test report The test report shall contain at least the following information: — all data necessary for the identification of the sample; — a reference to this European Standard; — the results and the units in which the results have been expressed; — any particular points observed in the course of the test; — any operations not specified in the method or regarded as optional which might have affected the results © BSI July 2002 blank BS EN 12946:2000 Bibliography VDLUFA, Manual II of analysing methods for fertilizers VDLUFA-Verlag, Bismarckstralße 41 A, D-64 293 Darmstadt EEC 77/535:1977, Council directive of 22.06.1977 on the approximation of laws in Member states regarding sampling and testing of fertilizers © BSI July 2002 BS EN 12946:2000 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: +44 (0)20 8996 9000 Fax: +44 (0)20 8996 7400 BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of 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