1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Part 2: Colourimetric titrationThe European Standard EN 62021-2:2007 has the status of a British St
2、andardICS 29.040.10Insulating liquids Determination of acidity BRITISH STANDARDBS EN 62021-2:2007BS EN 62021-2:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 August 2007 BSI 2007ISBN 978 0 580 57720 8Amendments issued since publicatio
3、nAmd. No. Date Commentscontract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations. National forewordThis British Standard is the UK implementation of EN 62021-2:2007. It is identical to IEC 62021-2:2007.The UK particip
4、ation in its preparation was entrusted to Technical Committee GEL/10, Fluids for electrotechnical applications.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a EUROPEAN STA
5、NDARD EN 62021-2 NORME EUROPENNE EUROPISCHE NORM July 2007 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2007 CENELEC - All ri
6、ghts of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 62021-2:2007 E ICS 29.040.10 English version Insulating liquids - Determination of acidity - Part 2: Colourimetric titration (IEC 62021-2:2007) Liquides isolants - Dtermination de lacidit - Partie 2
7、: Titrage colorimtrique (CEI 62021-2:2007) Isolierflssigkeiten - Bestimmung des Suregehaltes - Teil 2: Kolorimetrische Titration (IEC 62021-2:2007) This European Standard was approved by CENELEC on 2007-07-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipul
8、ate 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 CENELEC member. This European Standard
9、 exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national
10、electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Sw
11、itzerland and the United Kingdom. EN 62021-2:2007 2 Foreword The text of document 10/692/FDIS, future edition 1 of IEC 62021-2, prepared by IEC TC 10, Fluids for electrotechnical applications, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62021-2 on 2007-07-01. The
12、 following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2008-04-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2010-07-01 Annex ZA has
13、been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 62021-2:2007 was approved by CENELEC as a European Standard without any modification. _ 3 EN 62021-2:2007 CONTENTS INTRODUCTION.4 1 Scope 5 2 Normative references .5 3 Terms and definitions .6 4 Principle.6 5 Reag
14、ents6 5.1 Titration reagent. .6 5.2 Titration solvent.7 5.3 Potassium hydrogen phthalate, primary standard .7 5.4 Standard hydrochloric acid solution7 5.5 Alkali Blue 6B indicator solution .7 5.6 Cobalt nitrate solution7 6 Apparatus.7 6.1 Titration vessel7 6.2 Stirrer7 6.3 Burette 7 7 Sampling7 8 Pr
15、ocedure 8 8.1 Standardization of alcoholic potassium hydroxide solution 8 8.2 Blank titration 8 8.3 Sample titration .9 9 Calculation of results 9 10 Precision9 10.1 Repeatability .9 10.2 Reproducibility.10 11 Report10 Annex A (informative) Determination of acidity in electrical insulating oils by p
16、hotometric titration11 Annex ZA (normative) Normative references to international publications with their corresponding European publications16 Figure A.1 Molecular structure of para-naphtolbenzein indicator in (I) acidic media and (II) basic media 14 Figure A.2 UV spectra of para-naphthol-benzein i
17、ndicator in toluene/2-propanol/water solution in (a) acidic media, (b) basic media.15 EN 62021-2:2007 4 INTRODUCTION The standardized method given in IEC 62021-1 is a method for measurement of acidity in used and unused mineral oil and is a potentiometric titration requiring special instrumentation
18、for measurement of acidity. Historically, acidity of insulating oil was measured by colourimetric titration as described in IEC 60296, 1982 edition. With the revision of IEC 60296, the colourimetric titration was deleted as that method used high volumes of sample and solvent, generating undesirable
19、volumes of waste. However, there is still a market requirement for having colourimetric titration as many labs use this method. Health and safety This International Standard does not purport to address all the safety problems associated with its use. It is the responsibility of the user of the Stand
20、ard to establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use. The mineral oils which are the subject of this standard should be handled with due regard to personal hygiene. Direct contact with eyes may cause slight irritation. In the
21、 case of eye contact, irrigation with copious quantities of clean running water should be carried out and medical advice sought. Some of the tests specified in this standard involve the use of processes that could lead to a hazardous situation. Attention is drawn to the relevant standard for guidanc
22、e. This standard involves mineral oils, chemicals and used sample containers. The disposal of these items should be carried out in accordance with current national legislation with regard to the impact on the environment. Every precaution should be taken to prevent the release into the environment o
23、f mineral oil. 5 EN 62021-2:2007 INSULATING LIQUIDS DETERMINATION OF ACIDITY Part 2: Colourimetric titration 1 Scope This part of IEC 62021 describes a procedure for determination of the acidity of unused and used electrical mineral insulating oils. NOTE 1 In unused and used mineral insulating oils,
24、 the constituents that may be considered to have acidic characteristics include organic acids, phenolic compounds, some oxidation products, resins, organometallic salts and additives. The method may be used to indicate relative changes that occur in a mineral insulating oil during use under oxidizin
25、g conditions that may or may not be shown by other properties of the resulting mineral oil. The acidity can be used in the quality control of unused mineral oil. As a variety of oxidation products present in used mineral oil contribute to acidity and these products vary widely in their corrosion pro
26、perties, the test cannot be used to predict corrosiveness of a mineral oil under service conditions. NOTE 2 The acidity results obtained by this test method may or may not be numerically the same as those obtained by potentiometric methods, but they are generally of the same magnitude. The potentiom
27、etric method uses an endpoint at pH 11,3 to ensure titration of all species, whereas the colourimetric methods uses an indicator changing colour at approximately pH 9,5. This may lead to slightly higher results for oils with acidities above 0,3 mg KOH/g oil when using the potentiometric method. 2 No
28、rmative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60475: Method of sampling
29、liquid dielectrics IEC 60567: Oil-filled electrical equipment Sampling of gases and of oil for analysis of free and dissolved gases Guidance ISO 5725: Accuracy (trueness and precision) of measurement methods and results ISO 6619: Petroleum products and lubricants Neutralization number Potentiometric
30、 titration method EN 62021-2:2007 6 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 acidity quantity of base, expressed in milligrams of potassium hydroxide per gram of sample, required to titrate colourimetrically a test portion in a specifi
31、ed solvent to the neutralization point of Alkali Blue 6B 3.2 unused oil mineral insulating oil that has not been used in, or been in contact with electrical equipment 4 Principle The test portion is dissolved in a specified solvent and titrated colourimetrically with alcoholic potassium hydroxide to
32、 a specified colour using Alkali Blue 6B indicator. 5 Reagents Only reagents of recognized analytical grade and de-ionized water or water of equivalent purity shall be used. 5.1 Titration reagent Standard alcoholic solution 0,05 mol/l potassium hydroxide. Add 3,0 g of potassium hydroxide to 1 000 ml
33、 10 ml of 2-propanol. Boil gently for 10 min to effect solution. Cool and stopper the flask. Allow the solution to stand in the dark for 2 days and then filter the supernatant liquid through a 5 m membrane filter. Store in a suitable amber glass bottle. The concentration of this solution is approxim
34、ately 0,05 mol/l and shall be standardized as described in 8.1. For periodic tests on equipment in service, faster titration may be achieved by the use of 0,1 mol/l potassium hydroxide by agreement between the laboratory and the equipment owner, although this may result in poorer precision and detec
35、tion limit. Commercial alcoholic potassium hydroxide solution may be used, if necessary diluting to 0,05 mol/l with 2-propanol. This shall be standardized as described in 8.1. Store and use in such a manner that the solution is protected from atmospheric carbon dioxide and in such a way that it does
36、 not come into contact with cork, rubber or saponifiable stopcock grease. The solution may be protected by inert gas or by means of a guard tube containing soda-lime absorbent. 7 EN 62021-2:2007 5.2 Titration solvent 2-propanol (isopropanol; IPA), pure. 5.3 Potassium hydrogen phthalate, primary stan
37、dard This should be dried before use for 2 h at 105 C. 5.4 Standard hydrochloric acid solution A 0,1 mol/l solution of hydrochloric acid in de-ionized water, prepared as in ISO 6619, may be used. Other acids may be used, provided they are certified against a primary standard. 5.5 Alkali blue 6B indi
38、cator solution Dissolve 2 g 0.1 g of alkali blue 6B in 100 ml of 2-propanol or azeotropic ethanol containing 1 ml of the hydrochloric acid solution. After 24 h, carry out a titration to check whether the indicator has been sufficiently sensitized. The indicator is satisfactory if the colour changes
39、distinctly from blue to red comparable to that of a 10 % solution of cobalt nitrate. If sensitization is insufficient, repeat the addition of the hydrochloric acid solution and check again after 24 h. Continue until sensitization is satisfactory. Filter and store in a brown bottle in the dark. Comme
40、rcial alkali blue 6B solution may be used as an alternative if the concentration is within the range 0,05 % to 5 %. If the concentration is not 2 %, the amount added to the solvent in 8.2 and 8.3 should be adjusted to maintain the same ultimate concentration. 5.6 Cobalt nitrate solution Co(NO3)2.6H2
41、O solution, 10 % in water. 6 Apparatus 6.1 Titration vessel This should be as small as possible, sufficient to contain the solvent, sample and stirrer and be inert to the reagents. Glass conical vessels are preferred. 6.2 Stirrer Stirring may be manual by swirling the solution on the titration vesse
42、l, or mechanically using a variable speed stirrer fitted with a propeller, paddle or magnetic bar of chemically inert surface material. 6.3 Burette A burette or syringe capable of adding aliquots of 0,001 ml shall be used. 7 Sampling Samples shall be taken following the procedure given in IEC 60475
43、and/or IEC 60567. Ensure that the test portion is representative by thoroughly mixing, as any sediment present may be acidic or have adsorbed acidic material from the liquid phase. EN 62021-2:2007 8 8 Procedure Rinse and fill the burette with 0,05 mol/l alcoholic potassium hydroxide solution (5.1).
44、Standardize the alcoholic potassium hydroxide solution at least every two weeks against potassium hydrogen phthalate (5.3) or certified standard 0,1 mol/l acid. Carry out a blank titration on the solvent (5.2) each day and after changing to a fresh batch of solvent. 8.1 Standardization of alcoholic
45、potassium hydroxide solution Standardize the alcoholic potassium hydroxide solution, using a suitable indicator, against 0,1 g to 0,16 g of potassium hydrogen phthalate, weighed to an accuracy of 0,000 2 g and dissolved in approximately 100 ml of carbon dioxide free water. Alternatively the standard
46、ization can be performed by potentiometric titration. Calculate the molarity M to the nearest 0,000 5 using Equation (1): Vpm=23,2040001Molarity (1) where m is the mass of potassium hydrogen phthalate, in grams; p is the percent purity of the potassium hydrogen phthalate; V is the volume of potassiu
47、m hydroxide solution, in millilitres. Alternatively, certified standard 0,1 mol/l acid may be used to standardize the alcoholic potassium hydroxide solution. Calculate the molarity M to the nearest 0,000 5 using Equation (2): 0A1MolarityVMV = (2) where V1is the volume of 0,1 mol/l standard acid used
48、 to titrate the solution, in millilitres; MAis the molarity of the standard hydrochloric acid; V0is the volume of potassium hydroxide solution, in millilitres. 8.2 Blank titration Perform a blank titration at a temperature not above 25 C on 10 ml 0,1 ml aliquots of the solvent containing 0,5 % of al
49、kali blue 6B indicator solution (5.5) using the standardized alcoholic potassium hydroxide solution. The endpoint shall be as soon as a colour change from blue to a red colour comparable to that of the cobalt nitrate solution (5.6) is obtained and persists for at least 15 s. Carry out triplicate titrations and calculate the mean result, in millilitres to the nearest 0,001 ml, as the blank value V0. 9 EN 62021-2:2007 Protect the solvent from atmospheric ca
