1、BSI Standards PublicationBS EN 12945:2014Liming materials Determination of neutralizingvalue Titrimetric methodsBS EN 12945:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 12945:2014. Itsupersedes BS EN 12945:2008 which is withdrawn.The UK participation in
2、its preparation was entrusted to TechnicalCommittee CII/37, Fertilisers and related chemicals.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible
3、 for its correctapplication. The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 79081 2ICS 65.080Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy an
4、d Strategy Committee on 30 April 2014.Amendments issued since publicationDate Text affectedBS EN 12945:2014EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12945 April 2014 ICS 65.080 Supersedes EN 12945:2008English Version Liming materials - Determination of neutralizing value - Titrimetric met
5、hods Amendements minraux basiques - Dtermination de la valeur neutralisante - Mthodes par titrimtrie Kalkdnger - Bestimmung des Neutralisationswertes - Titrimetrische Verfahren This European Standard was approved by CEN on 8 February 2014. CEN members are bound to comply with the CEN/CENELEC Interna
6、l 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 CEN-CENELEC Management Centre or to any CE
7、N 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 CEN-CENELEC Management Centre has the same status as the official versi
8、ons. 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, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, P
9、oland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2014 CEN All rights of exploitati
10、on in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12945:2014 EBS EN 12945:2014EN 12945:2014 (E) 2 Contents Page Foreword 3 Introduction .4 1 Scope 5 2 Normative references 5 3 Terms and definitions .5 4 Principle 5 5 Reagents .5 6 Apparatus .6 7 Sampling .6 8 P
11、rocedure .6 9 Calculation and expression of results for method A and method B 8 10 Precision .8 11 Test report 9 Annex A (informative) Results of an inter-laboratory trial to determine the neutralizing value . 10 Bibliography . 11 BS EN 12945:2014EN 12945:2014 (E) 3 Foreword This document (EN 12945:
12、2014) has 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 October 2014
13、and conflicting national standards shall be withdrawn at the latest by October 2014. 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. T
14、his document supersedes EN 12945:2008. The following changes have been made to the former edition: a) scope modified taking into account that method A is not applicable to liming materials with more than 3 % P2O5and that method B is applicable to all liming materials; b) reference to EN 14984 added
15、to the scope and the Bibliography; c) 9.2 amended by addition of an instruction concerning the use of correction factors; d) optional requirement concerning correction factors added to Clause 11 Test report; e) corrigendum EN 12945:2008/AC:2009 included; f) editorially revised. According to the CEN-
16、CENELEC Internal Regulations, the national standards organizations 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, Hungary
17、, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 12945:2014EN 12945:2014 (E) 4 Introduction Two different procedures are described (method A and method
18、 B) because the titration to pH 7,0 is not applicable to silicate liming materials due to the precipitation of compounds at this pH value. In method B the turning point at pH 4,8 on the titration curve is taken as the end-point of the titration. For carbonaceous liming materials the difference in th
19、e consumption of sodium hydroxide solution for back titration between the titration end-points of pH 4,8 and pH 7,0 is negligible. BS EN 12945:2014EN 12945:2014 (E) 5 1 Scope This European Standard specifies two methods for the determination of the neutralizing value (NV) of liming materials. Method
20、 A is applicable to all liming materials except silicate liming materials. Method B is applicable to all liming materials. Both methods do not correctly take into account the potential neutralizing value of material containing more than 3 % P2O5. For a more accurate agronomic assessment of products
21、containing more than 3 % P2O5determine the liming efficiency according to EN 14984. NOTE The methods described in ISO 6598 1 and ISO 7497 2 can be used for the determination of P2O5content. Further information on P analyses is given in 3 and 4. 2 Normative references The following documents, in whol
22、e or in part, are normatively referenced in this document and are 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 1482-2, Fertilizers and liming mater
23、ials Sampling and sample preparation Part 2: Sample preparation EN 12944-3:2001, Fertilizers and liming materials Vocabulary Part 3: Terms relating to liming materials EN ISO 3696, Water for analytical laboratory use Specification and test methods (ISO 3696) ISO 3310-1, Test sieves Technical require
24、ments and testing Part 1: Test sieves of metal wire cloth 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 12944-3:2001 apply. 4 Principle Dissolution of the sample in a specified quantity of hydrochloric acid standard solution. Determination of the ex
25、cess acid by back titration with a sodium hydroxide standard solution. 5 Reagents During the analysis, unless otherwise stated, use only reagents of recognised analytical grade. NOTE Commercially available solutions can be used. 5.1 Water, according to EN ISO 3696, grade 3. 5.2 Hydrochloric acid sta
26、ndard solution, c(HCl) = 0,5 mol/l. Determine the exact concentration of the solution by titration with sodium hydroxide standard solution (5.3) using phenolphthalein solution (5.4) as indicator. Apply the appropriate correction factor in the calculation of the results (see Clause 9). 5.3 Sodium hyd
27、roxide standard solution, c(NaOH) = 0,25 mol/l. BS EN 12945:2014EN 12945:2014 (E) 6 Determine the exact concentration of the standard solution by titration against approximately 2 g of dried potassium hydrogen phthalate (KHC8H4O4), weighed to the nearest 0,001 g. The solution shall be stored in a po
28、lyethylene bottle and absorption of carbon dioxide during storage should be avoided. NOTE 1 ml of 0,25 mol/l sodium hydroxide solution is equivalent to 51,055 mg of potassium hydrogen phthalate. Apply the appropriate correction factor in the calculation of the results (see Clause 9). 5.4 Phenolphtha
29、lein indicator solution. Dissolve 0,25 g of phenolphthalein in 150 ml of ethanol with a mass fraction of 93 % and dilute with water to 250 ml. Use the phenolphthalein solution (5.4) as an indicator. 5.5 Hydrogen peroxide solution. Dilute one volume of hydrogen peroxide (H2O2) = 30 g/100 ml with four
30、 volumes of water. 6 Apparatus Usual laboratory apparatus and, in particular, the following: 6.1 Test sieve, conforming to the requirements of ISO 3310-1, of nominal aperture size 250 m. 6.2 pH meter, minimum sensitivity 0,05 pH units, with a suitable glass electrode and a calomel or other reference
31、 electrode or a combined electrode, calibrated using two buffer solutions whose pH values cover the range pH 4 to pH 7. 6.3 Mechanical stirrer, e.g. magnetic stirrer. 6.4 Desiccator. 7 Sampling Sampling is not part of the method specified in this European Standard. A recommended sampling method is d
32、escribed in EN 1482-1 5. Prepare the sample of the liming materials in accordance with EN 1482-2. 8 Procedure 8.1 Preparation of the test sample Dry the test sample at (105 2) C to constant mass. Record the as-received (mw) and dry (md) masses. Grind the sample so that it passes the 250 m test sieve
33、 (6.1). Mix thoroughly and store the sample in a desiccator (6.4). BS EN 12945:2014EN 12945:2014 (E) 7 8.2 Determination 8.2.1 Method A 8.2.1.1 Test portion Weigh about 0,5 g, to the nearest 0,001 g, of burnt or hydrated lime or 1 g of ground limestone or ground marl (prepared according to 8.1) into
34、 a 250 ml conical flask. 8.2.1.2 Titration Add 50 ml of the hydrochloric acid standard solution (5.2) with continuous shaking and boil gently for 10 min, using boiling granules. Cool to ambient temperature. Transfer quantitatively into a 250 ml beaker and insert the electrodes of the pH meter (6.2)
35、and a stirrer (6.3). Titrate with the sodium hydroxide standard solution (5.3) with moderate stirring (avoid splashing) until a pH of 7,0 is stable for 1 min whilst stirring is maintained. 8.2.2 Method B 8.2.2.1 Test portion Weigh about 0,5 g, to the nearest 0,001 g, of the prepared test sample (8.1
36、) into a 250 ml conical flask. 8.2.2.2 Titration Rinse the inside walls of the flask with 10 ml of water. Add 35 ml of the hydrochloric acid standard solution (5.2) with continuous shaking. Heat and boil gently for 10 min to dissolve the sample using boiling granules. Stir continuously. Cool to ambi
37、ent temperature, then dilute with water to about 100 ml and add 5 ml of hydrogen peroxide solution (5.5). NOTE Ferrous ions in silicate liming materials are oxidized by hydrogen peroxide to ferric ions before titration, because ferrous ions otherwise would consume hydrogen ions during titration. Tra
38、nsfer quantitatively into a 200 ml graduated flask; make up the volume with water and mix. Pass through a dry filter into a dry container, discarding the initial portion. Pipette an aliquot portion of 100 ml of the solution into a 250 ml beaker. Insert the electrodes of the pH meter (6.2) and a stir
39、rer (6.3). Titrate with the sodium hydroxide standard solution (5.3) with moderate stirring (avoid splashing) until a pH of 4,8 is stable for 1 min (whilst stirring is maintained). BS EN 12945:2014EN 12945:2014 (E) 8 9 Calculation and expression of results for method A and method B 9.1 Calculate the
40、 neutralizing value of the dried product, Nd, according to Formula (1) AmfVMAfVMN=t222111d100)(0,028(1) where 0,028 is the factor to convert hydrochloric acid standard solution into CaO; M1is the molarity of hydrochloric acid standard solution (5.2), in mol/l; V1is the total volume of hydrochloric a
41、cid standard solution (5.2), in millilitres; f1is the factor of hydrochloric acid standard solution (5.2); A is equal to 1 for method A, and the factor of the taken aliquot is 0,5 for method B; M2is the molarity of sodium hydroxide standard solution (5.3), in mol/l; V2is the volume of sodium hydroxi
42、de standard solution (5.3), in millilitres; f2is the factor of sodium hydroxide standard solution (5.3); mtis the mass of the test portion in the aliquot portion taken, in grams. 9.2 Calculate the neutralizing value of the “as-received” product, Nar, according to Formula (2) wddarmmNN = (2) where Nd
43、is the neutralizing value of the dried sample; mdis the mass of the sample after drying, in grams; mwis the mass of the sample before drying, in grams. The result shall be taken as the arithmetic mean of at least two determinations. Expressions of results do not contain any correction factors to tak
44、e into account material with a content of P2O5greater than 3 %. 10 Precision 10.1 General The precision of the method was established by an inter-laboratory trial carried out in 1999 in accordance with ISO 5725:1994 6. The values obtained for repeatability limit and reproducibility limit are express
45、ed for the 95 % probability level are not applicable to concentration ranges and matrices other than those given. NOTE The repeatability limits and reproducibility limits obtained from the inter-laboratory trial for each product being tested are given in Annex A. BS EN 12945:2014EN 12945:2014 (E) 9
46、10.2 Repeatability The absolute difference between two independent single test results, obtained using the same method on identical test material in the same laboratory by the same operator using the same equipment within the shortest feasible time interval will exceed the repeatability limit (r) on
47、 average not more than once in 20 cases in the normal and correct operation of the method. The value is: r = 2,30 % (relative) at a mean mass fraction of 53 % CaO. 10.3 Reproducibility The absolute difference between two independent single test results, obtained using the same method on identical te
48、st material in different laboratories with different operators using different equipment will exceed the reproducibility limit (R) on average not more than once in 20 cases in the normal and correct operation of the method. The value is: R = 12,64 % (relative) at a mean mass fraction of 53 % CaO. 11
49、 Test report The test report shall contain at least the following information: a) all data necessary for the identification of the sample; b) a reference to this European Standard, i.e. EN 12945; c) the method used (method A or method B); d) the results and the units in which the results have been expressed; e) any particular points observed in the course of the test; f) optionally a statement that correction factors for materials containing more than 3 % P2O5are not included; g) any operations not specified in the method or regarde
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