EN 16198-2012 en Fertilizers - Determination of magnesium by complexometry《肥料 配位滴定法测定镁含量》.pdf

1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 16198:2012Fertilizers Determination ofmagnesium by complexometryBS EN 16198:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 16198

2、:2012. It supersedes DD CEN/TS 16198:2011, which is withdrawn.The UK participation in its preparation was entrusted to T e c h n i c a l C o m m i t t e e C I I / 3 7 , F e r t i l i s e r s a n d r e l a t e d c h e m i c a l s .A list of organizations represented on this committee can be obtained

3、on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2012. Published by BSI Standards Limited 2012.ISBN 978 0 580 78186 5 ICS 65.080 Compliance with a

4、British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2012.Amendments issued since publicationDate T e x t a f f e c t e dBS EN 16198:2012EUROPEAN STANDARD NORME EUROPENNE E

5、UROPISCHE NORM EN 16198 November 2012 ICS 65.080 Supersedes CEN/TS 16198:2011English Version Fertilizers - Determination of magnesium by complexometry Engrais - Dosage du magnsium par complexomtrie Dngemittel - Komplexometrische Bestimmung von Magnesium This European Standard was approved by CEN on

6、6 October 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

7、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

8、 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,

9、Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Ave

10、nue 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 16198:2012: EBS EN 16198:2012EN 16198:2012 (E) 2 Contents Page Foreword 31 Scope 42 Normative references 43 Terms and definitions .44 Principle 45

11、Sampling .46 Reagents .57 Apparatus .68 Preparation of the extraction solution .69 Procedure .69.1 Control test .69.2 Aliquot samples to be taken .79.3 Titration in the presence of Eriochrome black-T 79.4 Titration in the presence of calcein or of calcon carbonic acid .710 Calculation and expression

12、 of the result 711 Remarks 712 Precision .812.1 Inter-laboratory test .812.2 Repeatability .812.3 Reproducibility .813 Test report 9Annex A (informative) Statistical results of the inter-laboratory test . 10Bibliography . 12BS EN 16198:2012EN 16198:2012 (E) 3 Foreword This document (EN 16198:2012) h

13、as been prepared by Technical Committee CEN/TC 260 “Fertilizers and liming materials”, the secretariat of which is held by DIN. 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 confli

14、cting 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 s

15、upersedes CEN/TS 16198:2011. The following changes have been made to the former edition: a) the CEN Technical Specification has been adopted as a European Standard; b) the document has been editorially revised. This document has been prepared under a mandate given to CEN by the European Commission a

16、nd the European Free Trade Association. 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 Yug

17、oslav 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. BS EN 16198:2012EN 16198:2012 (E) 4 1 Scope Thi

18、s European Standard specifies a method for the determination of magnesium in fertilizer extracts by complexometry. The method is applicable to the following EC fertilizer extracts for which the determination of total magnesium and/or water-soluble magnesium is provided for according to the Regulatio

19、n (EC) No 2003/2003, Annex I 3: fertilizers listed in 3, Annex I: straight nitrogenous fertilizers, type 1b + 1c (calcium magnesium nitrate), type 7 (magnesium sulfonitrate), type 8 (nitrogenous fertilizers with magnesium) and straight potassic fertilizers, type 2 (enriched kainite), type 4 (potassi

20、um chloride containing magnesium), type 6 (potassium sulfate containing magnesium salt); fertilizers listed in 3, Annex I D relating to secondary nutrients. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its

21、application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 1482-2, Fertilizers and liming materials Sampling and sample preparation Part 2: Sample preparation EN 12944-1:1999, Fertili

22、zers and liming materials and soil improvers Vocabulary Part 1: General terms EN 12944-2:1999, Fertilizers and liming materials and soil improvers Vocabulary Part 2: Terms relating to fertilizers EN 15960, Fertilizers Extraction of total calcium, total magnesium, total sodium and total sulfur in the

23、 forms of sulfates EN 15961, Fertilizers Extraction of water soluble calcium, magnesium, sodium and sulfur in the form of sulfates 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999 apply. 4 Principle The magnesium is sol

24、ubilised according to EN 15960 or EN 15961. First titration: with EDTA of Ca and Mg in the presence of Eriochrome black-T. Second titration: with EDTA of Ca in the presence of calcein or of calcone carbonic acid. Determination of magnesium by difference. 5 Sampling Sampling is not part of the method

25、 specified in this document. A recommended sampling method is given in EN 1482-1. Sample preparation shall be carried out in accordance with EN 1482-2. Grinding of the laboratory sample is recommended for homogeneity reasons. BS EN 16198:2012EN 16198:2012 (E) 5 6 Reagents 6.1 Magnesium standard solu

26、tion, c = 0,05 mol/l. 6.1.1 Dissolve 1,232 g of magnesium sulfate (MgSO47H2O) in the hydrochloric acid solution (6.11) and make up to 100 ml with the same acid, or 6.1.2 Weigh 2,016 g of magnesium oxide, previously calcined to remove all traces of carbonation. Place it in a beaker with 100 ml of wat

27、er. Stir in approximately 120 ml of hydrochloric acid (6.12). After dissolution, transfer quantitatively into a graduated 1 000 ml flask. Make up to volume and mix. 1 ml of these solutions should contain 1,216 mg of Mg (= 2,016 mg of MgO). The laboratory is responsible for testing the strength of th

28、is standard solution. 6.2 EDTA solution, c = 0,05 mol/l. Weigh 18,61 g of the dihydrated disodium salt of ethylenediaminetetraacetic (EDTA) (C10H14N2Na2O8,2H2O), place it in a beaker (7.4) and dissolve in 600 ml to 800 ml of water. Transfer the solution quantitatively into a graduated flask (7.3). M

29、ake up the volume and mix. Check this solution with the standard solution (6.1) by taking a sample of 20 ml of the latter and by titration according to the analytical procedure described in 9.2. 1 ml of the EDTA solution should correspond to 1,216 mg of Mg (= 2,016 mg of MgO) and to 2,004 mg of Ca (

30、= 2,804 mg CaO) (see remarks 11.1 and 11.6). 6.3 Calcium standard solution, c = 0,05 mol/l. Weigh 5,004 g of dry calcium carbonate. Place it in a beaker with 100 ml of water. Progressively stir in 120 ml of hydrochloric acid (6.12). Bring to the boil in order to drive off the carbon dioxide, cool, t

31、ransfer quantitatively into a graduated 1 l flask, make up the volume with water and mix. Check this solution against the EDTA solution (6.2) following analytical procedure (9.3). 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 soluti

32、on (6.2). 6.4 Calcein indicator. Carefully mix in a mortar 1 g of calcein with 100 g of sodium chloride. Use 10 mg of this mixture. The indicator changes from green to orange. Titration shall be carried out until an orange is obtained which is free from green tinges. 6.5 Calcon carbonic acid indicat

33、or. Dissolve 400 mg of calcon carbonic in 100 ml of methanol. This solution may only be kept for approximately four weeks. Use three drops of this solution. The indicator changes from red to blue. Titration shall be carried out until a blue is obtained which is free from red tinges. 6.6 Eriochrome b

34、lack-T indicator. Dissolve 300 mg of Eriochrome black-T in a mixture of 25 ml of propanol-1 and 15 ml of triethanolamine. This solution may only be kept for approximately four weeks. Use three drops of this solution. This indicator turns from red to blue and titration shall be carried out until a bl

35、ue is obtained which is free from red tinges. It BS EN 16198:2012EN 16198:2012 (E) 6 changes colour only when magnesium is present. If necessary add 1 ml of the magnesium standard solution (6.1). When both calcium and magnesium are present the EDTA first forms a complex with the calcium and then wit

36、h the magnesium. In that case two elements are determined concurrently. 6.7 Potassium cyanide solution, aqueous solution of w(KCN) = 2 %. SAFETY PRECAUTIONS Do not pipette by mouth and see 11.7. 6.8 Solution of potassium hydroxide and potassium cyanide. Dissolve 280 g of KOH and 66 g of KCN in water

37、, make up the volume to 1 l and mix. 6.9 Buffer solution, pH = 10,5. In a graduated flask (7.5), dissolve 33 g of ammonium chloride in 200 ml of water, add 250 ml of ammonia (20= 0,91 g/ml) make up the volume with water and mix. Check the pH of the solution regularly. 6.10 Diluted hydrochloric acid,

38、 one volume of hydrochloric acid (20= 1,18 g/ml) plus one volume of water. 6.11 Hydrochloric acid solution, approximately c = 0,5 mol/l. 6.12 Hydrochloric acid solution, approximately c = 1 mol/l. 6.13 Sodium hydroxide solution, c = 5 mol/l. 7 Apparatus 7.1 Magnetic or mechanical stirrer. 7.2 pH met

39、er. 7.3 1 000 ml graduated flask. 7.4 1 000 ml beaker. 7.5 500 ml graduated flask. 7.6 400 ml beaker. 8 Preparation of the extraction solution Prepare the extraction solution according to EN 15960 or EN 15961. 9 Procedure 9.1 Control test Carry out a determination on aliquot parts of solutions (6.1

40、and 6.3) such that the Ca/Mg ratio is approximately equal to that of the solution to be analysed. To this end take v1ml of Ca standard solution (6.3) and (v2-v1) ml of standard solution (6.1), where v1and v2are the volumes, in millilitres, of the EDTA solution used in the two titrations performed on

41、 the solution to be analysed. This procedure is correct only if the solutions of EDTA, calcium and magnesium are exactly equivalent. If this is not the case, it is necessary to make corrections. BS EN 16198:2012EN 16198:2012 (E) 7 9.2 Aliquot samples to be taken The aliquot part will as far as possi

42、ble contain between 9 mg and 18 mg of magnesium (= 15 mg to 30 mg of MgO). 9.3 Titration in the presence of Eriochrome black-T Pipette an aliquot part (9.2) of the solution to be analysed into a beaker (7.6). Neutralise the surplus acid with the sodium hydroxide solution (6.13) using the pH meter. D

43、ilute with water to approximately 100 ml. Add 5 ml of the buffer solution (6.9). The pH measured shall be 10,5 0,1. Add 2 ml of the potassium cyanide solution (6.7) and three drops of the Eriochrome black-T indicator (6.6). Titrate with the EDTA solution (6.2). Stir gently with the stirrer (7.1) (se

44、e 11.2, 11.3 and 11.4). Take v2as the volume, in millilitres, of the EDTA solution (6.2). 9.4 Titration in the presence of calcein or of calcon carbonic acid Pipette an aliquot part of the solution to be analysed equal to that taken from the above titration (9.3) and place it in a beaker (7.6). Neut

45、ralise the surplus acid with the sodium hydroxide solution (6.13) using the pH meter. Dilute with water to about 100 ml. Add 10 ml of the KOH/KCN solution (6.8) and the indicator (6.4 or 6.5). Stir gently with the stirrer (7.1) titrate with the EDTA solution (6.2) (see 11.2, 11.3 and 11.4). Take v1a

46、s the volume, in millilitres, of the EDTA solution (6.2). 10 Calculation and expression of the result For the EEC fertilizers to which the method is applicable (5 g of fertilizer in 500 ml of extract), calculate the MgO content as a mass fraction, wMgO, in percent of the fertilizer according to Form

47、ula (1). MTvvw=)(12MgO(1) For the EEC fertilizers to which the method is applicable (5 g of fertilizer in 500 ml of extract), calculate the Mg content as a mass fraction, wMg, in percent of the fertilizer according to Formula (2). MTvvw)(12=Mg(2) where v1is the volume of the EDTA solution (6.2), in

48、millilitres, used for the titration in the presence of calcein or calcon carbonic acid; v2is the volume of the EDTA solution (6.2), in millilitres, used for the titration in the presence of Eriochrome black-T; M is the mass of the sample present in the aliquot part taken, in grams; T is 0,201 6 mol/

49、l of the EDTA solution (6.2) 0,05; T is 0,121 6 mol/l of the EDTA solution (6.2) 0,05. 11 Remarks 11.1 The stoichiometric EDTA-metal ratio in the complexometric analyses is always 1:1 whatever the valency of the metal and in spite of the fact that EDTA is quadrivalent. The EDTA titration solution and the standard solutions will therefore be molar and not normal. BS EN 16198:2012EN 16198:2012 (E) 8 11.2 Complexometric indicators are often sensitive to air. The solution may lose colour during