BS EN 27888-1993 Water quality - Method for the determination of electrical conductivity《水质 电导率测定方法》.pdf

1、BRITISH STANDARD BS EN 27888:1993 BS 6068-2.35: 1993 ISO 7888:1985 Water quality Method for the determination of electrical conductivity The European Standard EN27888:1993 has the status of a British Standard UDC 628.1/.3:620.1:543.3:541.133BSEN 27888:1993 This British Standard, having been prepared

2、 under the direction of the Environment and Pollution Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15November1993 BSI 03-1999 The following BSI references relate to the work on this standard: Committee reference EPC/44 Draft announced

3、in BSI News August 1992 ISBN 0 580 21204 1 Cooperating organizations The European Committee for Standardization (CEN), under whose supervision this European Standard was prepared, comprises the national standards organizations of the following countries: Austria Oesterreichisches Normungsinstitut Be

4、lgium Institut belge de normalisation Denmark Dansk Standardiseringsraad Finland Suomen Standardisoimisliito, r.y. France Association franaise de normalisation Germany Deutsches Institut fr Normung e.V. Greece Hellenic Organization for Standardization Iceland Technological Institute of Iceland Irela

5、nd National Standards Authority of Ireland Italy Ente Nazionale Italiano di Unificazione Luxembourg Inspection du Travail et des Mines Netherlands Nederlands Normalisatie-instituut Norway Norges Standardiseringsforbund Portugal Instituto Portugus da Qualidade Spain Asociacin Espaola de Normalizacin

6、y Certificacin Sweden Standardiseringskommissionen i Sverige Switzerland Association suisse de normalisation United Kingdom British Standards Institution Amendments issued since publication Amd. No. Date CommentsBSEN27888:1993 BSI 03-1999 i Contents Page Cooperating organizations Inside front cover

7、National foreword ii Foreword 2 Text of EN 27888 3 National annex NA (informative) Committees responsible Inside back coverBSEN 27888:1993 ii BSI 03-1999 National foreword This British Standard has been prepared under the direction of the Environment and Pollution Standards Policy Committee and is t

8、he English language version of EN27888, Water quality Determination of electrical conductivity published by the European Committee for Standardization (CEN), which endorses ISO7888:1985, published by the International Organization for Standardization (ISO). It supersedes BS6068-2.35:1989, which is n

9、ow withdrawn. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This docum

10、ent comprises a front cover, an inside front cover, pages i and ii, theEN title page, pages2 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cove

11、r.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 27888 September 1993 UDC 628.1/.3:620.1:543.3:541.133 Descriptors: Water tests, water, quality, electrical properties, resistance English version Water quality Determination of electrical conductivity (ISO7888:1985) Qualit de leau Dtermination d

12、e la conductivit lectrique (ISO7888:1985) Wasserbeschaffenheit Bestimmung der elektrischen Leitfhigkeit (ISO7888:1985) This European Standard was approved by CEN on1993-09-10. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this Eur

13、opean 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 (Englis

14、h, 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 electrotechnical committees of Austria, Belgium, D

15、enmark, Finland, France, Germany, 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 3

16、5, B-1050 Brussels 1993 Copyright reserved to CEN members Ref. No. EN 27888:1993 EEN27888:1993 BSI 03-1999 2 Foreword This European Standard has been taken over by CEN/TC230 “Water analysis” from the work of ISO/TC147 “Water quality” of the International Organization for Standardization (ISO). It wa

17、s decided by the Resolution BTS335/1990 to submit the Final Draft to the CEN members for voting by Unique Acceptance Procedure (UAP). The result of the Unique Acceptance Procedure was positive. This European Standard shall be given the status of a national standard, either by publication of an ident

18、ical text or by endorsement, at the latest by March1994, and conflicting national standards shall be withdrawn at the latest by March1994. In accordance with the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finlan

19、d, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. Contents Page Foreword 2 1 Scope and field of application 3 2 Definitions 3 3 Principle 3 4 Reagents 4 5 Apparatus 4 6 Sampling and samples 5 7 Procedure 5 7

20、.1 General 5 7.2 Temperature correction 5 8 Expression of results 7 8.1 Calculation 7 8.2 Repeatability 7 8.3 Standard deviation 7 8.4 Examples of reported results 7 9 Interferences 7 10 Test report 7 Bibliography 8 Table 1 Electrical conductivity of potassium chloride solutions 4 Table 2 Recommende

21、d cell constants for different ranges of electrical conductivity 4 Table 3 Temperature correction factor, f 25 , for the conversion of conductivity values of natural waters from C to25C 5 6 Table 4 Standard deviation of synthetic samples (KCl solutions) 7 Table 5 Standard deviation of natural waters

22、 7EN 27888:1993 BSI 03-1999 3 1 Scope and field of application This International Standard specifies a method for the measurement of the electrical conductivity of all types of water. Electrical conductivity can be used to monitor the quality of a) surface waters; b) process waters in water supply a

23、nd treatment plants; c) waste waters. The completeness of analysis for ionic constituents 1 to3can be checked using this method. In some cases absolute values are important, in other cases only relative changes are of concern. For interferences, see clause9. 2 Definitions 2.1 specific conductance; e

24、lectrical conductivity, the reciprocal of the resistance, measured under specified conditions, between the opposite faces of a unit cube of defined dimensions of an aqueous solution. For water quality examination, this is often expressed as “electrical conductivity” and may be used as a measure of t

25、he concentration of ionizable solutes present in the sample (definition taken from ISO6107/2) it is expressed in siemens per metre 1) NOTEThe symbols B and 0 are also used for electrical conductivity (seeISO31/5). 2.2 cell constant, K quantity, in reciprocal metres, given by the equation where l is

26、the length, in metres, of an electrical conductor; A is the effective cross-sectional area, in square metres, of an electrical conductor. The cell constant results from the geometry of the cell; it can be empirically determined. 2.3 temperature coefficient of electrical conductivity, 2) the temperat

27、ure coefficient of conductivity ,25 , 4,5is given by the Equation where25 and C are the temperatures at which the electrical conductivities 25and respectively were measured 2.4 temperature correction factors, f factors used to correct for the temperature dependence of electrical conductivity in orde

28、r to make comparisons, it is essential that measurements are corrected to a chosen reference temperature, usually25,0C, even if the temperature of the water sample differs only slightly from that temperature conversions to the electrical conductivity at25C, 25 , can be made using the Equation where

29、is the temperature coefficient of electrical conductivity; is the electrical conductivity at the measured temperature, ; is the measuring temperature, in degrees Celsius, of the sample. 3 Principle Direct determination, using an appropriate instrument, of the electrical conductivity of aqueous solut

30、ions. The electrical conductivity is a measure of the current conducted by ions present in the water (“phenomenon of conductors of the second kind”), and depends on a) the concentration of the ions; b) the nature of the ions; c) the temperature of the solution; d) the viscosity of the solution. Pure

31、 water as a result of its own dissociation has an electrical conductivity at25C of5,4834S/m 6 (0,005483mS/m). 1) 1 S/m = 10 44S/cm = 10 3mS/m K l A - = 2) The temperature coefficient of electrical conductivity can be expressed in reciprocal kelvin or% perC.EN 27888:1993 4 BSI 03-1999 4 Reagents Duri

32、ng the analysis, unless otherwise stated, use only reagents of recognized analytical grade. 4.1 Water for preparing solutions and dilutions. Double distilled or de-ionized water; the electrical conductivity shall be 25 0,1mS/m. 4.2 Potassium chloride standard solution A, 7 c(KCl)=0,1mol/l. Dry a few

33、 grams of potassium chloride at105C for2h, and dissolve7,456g in water(4.1). Dilute to1000ml. The conductivity of this solution at25C, 25 , is1290mS/m. 4.3 Potassium chloride standard solution B, c(KCl)=0,01mol/l. Dilute100ml of solution A(4.2) with water(4.1) to1000ml. The conductivity of this solu

34、tion at25C, 25 , is141mS/m. 4.4 Potassium chloride standard solution C, c(KCl)=0,001mol/l. Dilute100ml of solution B(4.3) with water(4.1) to1000ml. Immediately before preparing this solution the water shall be freed from carbon dioxide by purging with pure nitrogen or by boiling. During work with th

35、ese solutions any contact with the atmosphere shall be minimized. Prepare this solution shortly before use. The conductivity of this solution at25C, 25 , is14,7mS/m. NOTETable 1 gives alternative concentrations of potassium chloride that can be used as standards of conductivity. 8,9 Table 1 Electric

36、al conductivity of potassium chloride solutions 4.5 Platinizing solution Dissolve1,5g of hydrogen hexachloroplatinate(IV) hexahydrate (H 2 PtCl 6 6H 2 O) in50ml of water containing0,0125g of lead(II) acetate Pb(C 2 H 3 O 2 ) 2 . 5 Apparatus 5.1 Instruments for measurement of electrical conductivity

37、The instrument may be of either of the following types: a) instrument equipped with a flow- or dip-type conductivity cell fitted with two or more electrodes; b) instrument fitted with electrodes of the induction type. Preferably instruments should be capable of discrete and continuous measurement bo

38、th in the laboratory and in the field. A flow-type conductivity cell from which air is excluded is essential for measurements of conductivities of less than1mS/m. The recommended electrode cell constant can be chosen fromTable 2 for each measuring range. Table 2 Recommended cell constants for differ

39、ent ranges of electrical conductivity Some instruments are equipped with a cell constant control. If this is not the case, the reading must be multiplied by the cell constant. 5.2 Electrodes Whenever platinum electrodes are used for precision measurements the electrodes shall be platinized (see the

40、note). Unplatinized electrodes may be used only for field and routine laboratory testing. NOTEIf platinization is necessary, the manufacturers instructions should be followed, or proceed as follows. Concentration of potassium chloride, c(KCl) Electrical conductivity at25C, 25 mol/l mS/m 0,0005 0,001

41、 0,005 0,01 0,02 0,05 0,1 0,2 7,4 14,7 72 141 277 670 1290 2480 Measuring range Recommended cell constant mS/m m 1 2 0,1 20 1 200 10 2 10 3 100 20 10 3 1 10 100 1000 5000EN 27888:1993 BSI 03-1999 5 Platinize the electrodes of the cell with platinizing solution(4.5). A suitable plating apparatus cons

42、ists of a6Vd.c. supply, a variable resistor, a milliammeter, and an electrode. The procedure for platinizing is not critical. Good platinized coatings are obtained using from1,5 to3C/cm 2of electrode area. For example for an electrode having a total area (both sides) of10cm 2 , the plating time at a

43、 current of20mA would be from12,5to25min. The current density may be from1 to4mA/cm 2of electrode area. Plate the electrodes one at a time with the aid of an extra electrode. During the plating, agitate the solution gently. When not in use, fill the cells with water to prevent the drying out of the

44、electrodes while in storage. 5.3 Thermometer, accurate to 0,1C, within the temperature range of measurement, shall be used for precise determinations. For routine measurements, a thermometer accurate to 0,5C is satisfactory. 5.4 Thermostatic bath, capable of being maintained at25,0 0,1C. For routine

45、 measurements, a tolerance of 0,5C is satisfactory. 6 Sampling and samples Collect the laboratory sample in a polyethylene bottle completely filled and tightly stoppered. Soda glass bottles shall not be used. Measurement of conductivity should be performed as soon as practicable, particularly when t

46、here is a possibility of an exchange of gases such as carbon dioxide or ammonia with the atmosphere, or a possibility of biological activity. Biological activity can be reduced by storing the samples in the dark at4C; however, samples shall be brought to equilibrium at the reference temperature of25

47、C before the conductivity is measured. No suitable preservative is known for samples taken for conductivity measurements. 7 Procedure 7.1 General Prepare the equipment for use as instructed by the manufacturer and ensure that an electrode cell of known cell constant appropriate to the desired measur

48、ing range is fitted (seeTable 2). The test portion depends on the equipment used. If the cell constant is not accurately known, determine the constant as given in clause5 using the potassium chloride standard solutions (4.2 to4.4) appropriate to each desired measuring range. Check the cell constant

49、at least once every6 months. Many instruments incorporate cell constant correction as an integral function and thus a direct reading of electrical conductivity is obtained. Otherwise multiply the conductance value obtained by the cell constant to obtain electrical conductivity. For high precision work, carry out the measurement of electrical conductivity when the sample and apparatus in direct contact with it has attained equilibrium at25,0 0,1C. Thus all