1、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 12946:1999 has the status of a British Standard ICS 65.080 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY
2、 COPYRIGHT LAWBS EN 12946:2000 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 1 July 2002 ISBN 0 580 35922 0 National foreword
3、 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: A list of organizations repr
4、esented 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 stan
5、dard 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 titrimetri
6、c 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
7、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
8、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. aid enquirers to understand the text; present to the responsible European committee any enquiries on th
9、e interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 9 and a back cover. The B
10、SI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments 13810 corrigendum 1 July 2002 Addition to clause 3EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12946 January 2000 ICS 65.080 Incorporating co
11、rrigendum February 2002 English version Liming materials Determination of calcium content and magnesium content Complexometric method Amendements calciques et/ou magnsiens Dtermination de la teneur en calcium et de la teneur en magnsium Mthode par complexomtrie Calcium-Magnesium-Bodenverbesserungsmi
12、ttel 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 n
13、ational 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
14、 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, Ge
15、rmany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 2000 CEN
16、 All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12946:2000 EEN 12946:2000 BSI 1 July 2002 2 Foreword This European Standard has been prepared by Technical Committee CEN/TC 260, Fertilizers and liming materials, the Secretariat of whic
17、h 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 Intern
18、al 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 a
19、nd the United Kingdom. Contents Page Foreword 2 1S c o p e 3 2 Normative references 3 3P r i n c i p l e 3 4R e a g e n t s 3 5 Apparatus 4 6S a m p l i n g 5 7 Procedure 5 8 Expression of results 6 9 Precision 6 10 Test report 7 Bibliography 9EN 12946:2000 BSI 1 July 2002 3 1 Scope This European St
20、andard 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 2 % (m/m) magnesium or those with a mass fraction more than 1 % P 2 O 5and is not applicable to silicat
21、e liming materials. 2 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 ame
22、ndments 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
23、and liming materials. ISO 3310-1, Test sieves Technical requirements and testing Part 1: Test sieves of metal wire cloth. 3 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/
24、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. 4 Reagents 4.1 General In principle, commercially available standard solutio
25、ns 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 1 part by volume of hydrochloric acid ( 20= 1,18 g/ml) to 1 part by volume of
26、 water. 4.3 Hydrochloric acid solution c(HCI) = 1 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 co
27、ntinuous 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 1 000 ml volumetric flask and dilute to the mark with water. Check the standard strength of the solution by titration with the EDTA
28、standard solution (4.7) according to 7.3. 1 ml of this solution should contain 2,004 mg of Ca (2,804 mg of CaO) and should correspond to 1 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 (MgSO
29、 4 7H 2 0) into a 100 ml volumetric flask, dissolve in hydrochloric acid solution (4.4) and dilute to the mark with the same solution. orEN 12946:2000 4 BSI 1 July 2002 4.6.2 Calcined magnesium oxide (MgO) at 600 C for 2 h. Weigh 2,016 g of the freshly calcined MgO into a 500 ml beaker, dissolve in
30、100 ml of water and 120 ml of hydrochloric acid solution (4.3). Transfer the solution into a 1 000 ml volumetric flask and dilute to the mark with water. 1 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
31、. 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; C 1O H 14 N 2 Na 2 O 8 2H 2 O) into a 1 000 ml volumetric flask and dilute to the mark with water. Check the standard strength of the
32、 solution by titration of 20 ml of the standard solution 4.6 according to 7.2.2. 1 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
33、 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 or
34、ange 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. Tit
35、ration 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
36、 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 1 ml of the standard solution (4.6). 4.11 Triethanolamine A
37、queus 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)NH 3solution) and dilute to the mark with wat
38、er. 4.13 Sodium hydroxide solution c(NaOH) = 5 mol/l. 5 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 m. 5.2 Pestle and mortar, each of porcelain, or mechanical grinder. 5.3 Electric ho
39、t 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.EN 12946:2000 BSI 1 July 2002 5 6 Sampling Sample the liming materials in accordance with EN 1482. 7 Procedu
40、re 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 m sieve. Mix the test sample thoroughly. 7.1.2 Preparation of test solution Weigh about 1 g to the neares
41、t 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 min. Allow to cool to ambient temperature under stirring. Transfer the solution quantitatively to a 500 ml volumetric flask, dilute to the
42、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
43、Take an aliquot portion, expected to contain between 15 mg and 30 mg of calcium and between 9 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 s
44、odium hydroxide solution (4.13) using the pH meter. Dilute with water to approximately 100 ml. Add 5 ml of the buffer solution (4.12). The pH should be 10,5 0,1. Add 5 ml Triethanolamine (4.11) and three drops of the eriochrome black T indicator (4.10). Stir gently with the stirrer (5.4) and titrate
45、 with the EDTA standard solution (4.7). NOTE 1 The use of triethanolamine is not required for products with a low content of impurities (e.g. iron). NOTE 2 In particular the eriochrome black T indicator and the calcon carbonic acid indicator are often sensitive to oxidation by air. Therefore, the so
46、lution may lose colour during titration. Add one or two drops of the corresponding indicator solution if this occurs. NOTE 3 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 tha
47、t 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 4 Observe the colour of the solution from horizontal position at the end of the titration
48、. 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 th
49、ymolphthalein 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 5 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 1 to 4 in 7.2.2). 7.3 Control test of the standard so
