1、Designation: D 1125 95 (Reapproved 2005)Standard Test Methods forElectrical Conductivity and Resistivity of Water1This standard is issued under the fixed designation D 1125; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cover the dete
3、rmination of theelectrical conductivity and resistivity of water. The followingtest methods are included:Range SectionsTest Method AField and Routine Laboratory 10 to 200 000 12 to 18Measurement of Static (Non-Flowing)SamplesS/cmTest Method BContinuous In-Line Measure 5 to 200 000 19 to 23ment S/cm1
4、.2 These test methods have been tested in reagent water. Itis the users responsibility to ensure the validity of these testmethods for waters of untested matrices.1.3 For measurements below the range of these test meth-ods, refer to Test Method D 5391.1.4 This standard does not purport to address al
5、l of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1066 Practice for
6、Sampling SteamD 1129 Terminology Relating to WaterD 1192 Specification for Equipment for Sampling Waterand Steam in Closed Conduits3D 1193 Specification for Reagent WaterD 2186 Test Method for Deposit-Forming Impurities inSteamD 2777 Practice for Determination of Precision and Bias ofApplicable Meth
7、ods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 4519 Test Method for On-Line Determination of Anionsand Carbon Dioxide in High Purity Water by CationExchange and Degassed Cation ConductivityD 5391 Test Method for Electrical Conductivity and Resis-tivity of a Fl
8、owing High Purity Water SampleE1 Specification for ASTM Liquid-in-Glass Thermometers3. Terminology3.1 Definitions:3.1.1 electrical conductivitythe reciprocal of the a-c re-sistance in ohms measured between opposite faces of acentimetre cube of an aqueous solution at a specified tempera-ture.NOTE 1Th
9、e unit of electrical conductivity is siemens per centimetre.(The previously used units of mhos/cm are numerically equivalent toS/cm.) The actual resistance of the cell, Rx, is measured in ohms. Theconductance, 1/Rx, is directly proportional to the cross-sectional area, A(in cm2), and inversely propo
10、rtional to the length of the path, L (in cm):1/Rx5 KA/LThe conductance measured between opposite faces of acentimetre cube, K, is called conductivity. Conductivity valuesare usually expressed in microsiemens/centimetre or insiemens/centimetre at a specified temperature, normally 25C.3.1.2 electrical
11、 resistivitythe a-c resistance in ohms mea-sured between opposite faces of a centimetre cube of anaqueous solution at a specified temperature.NOTE 2The unit of electrical resistivity is ohm-centimetre. The actualresistance of the cell, Rx, is measured in ohms, and is directly proportionalto the leng
12、th of the path, L (in cm), and inversely proportional to thecross-sectional area, A (in cm2):Rx5 RL/AThe resistance measured between opposite faces of a centi-metre cube, R, is called resistivity. Resistivity values areusually expressed in ohmcentimetre, or in megohm centime-tre, at a specified temp
13、erature, normally 25C.3.1.3 For definitions of other terms used in these methods,refer to Terminology D 1129.3.2 Symbols:Symbols:3.2.1 Symbols used in the equations in Sections 14 and 16are defined as follows:J = cell constant, cm1,K = conductivity at 25C, S/cm,1These test methods are under the juri
14、sdiction of Committee D19 on Water andare the direct responsibility of Subcommittee D19.03 on Sampling of Water andWater-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.Current edition approved April 1, 2005. Published April 2005. Originallyapproved in 1950. Last previous editi
15、on approved in 1999 as D 1125 95 (1999).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.1Copyright
16、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Kx= measured conductance, S,K1= conductivity of the KCl in the reference solution at thetemperature of measurement (Table 1), S/cm,K2= conductivity of the water used to prepare the referencesolut
17、ion, at the same temperature of measurement, S/cm,Q = temperature correction factor (see Section 11),R = resistivity at 25C, ohm cm,Rx= measured resistance, ohm.4. Significance and Use4.1 These test methods are applicable for such purposes asimpurity detection and, in some cases, the quantitative me
18、a-surement of ionic constituents dissolved in waters. Theseinclude dissolved electrolytes in natural and treated waters,such as boiler water, boiler feedwater, cooling water, and salineand brackish water.4.1.1 Their concentration may range from trace levels inpure waters (1)4to significant levels in
19、 condensed steam (seeTest Methods D 2186 and D 4519, and Ref (2), or pure saltsolutions.4.1.2 Where the principal interest in the use of conductivitymethods is to determine steam purity, see Ref (3). These testmethods may also be used for checking the correctness ofwater analyses (4).5. Interference
20、s5.1 Exposure of a sample to the atmosphere may causechanges in conductivity/resistivity, due to loss or gain ofdissolved gases. This is extremely important in the case of verypure waters with low concentrations of dissolved ionizedmaterials. The carbon dioxide, normally present in the air, candrast
21、ically increase the conductivity of pure waters by approxi-mately 1 S/cm. Contact with air should be avoided by usingflow-through or in-line cell where feasible. Chemically pureinert gases, such as nitrogen or helium, may be used to blanketthe surface of samples.5.2 Undissolved or slowly precipitati
22、ng materials in thesample can form a coating on the electrodes of the conductivitycell that may cause erroneous readings. For example, biofoul-ing of the cell or a build-up of filming amines may cause poorcell response. In most cases these problems can be eliminatedby washing the cells with appropri
23、ate solvents.5.3 If an unshielded cell is used to measure the resistivity/conductivity of high resistivity water there is a possibility ofelectrical pickup causing erroneous reading. For this reason itis recommended that conductivity cells for this application beof coaxial shielded type or equivalen
24、t, and that the cables andinstrument also be shielded.6. Apparatus6.1 Measuring CircuitThe instrument may be a manuallyoperated wheatstone bridge or the equivalent, or a directreading analog or digital meter. Instruments shall energize theconductivity cell with alternating current and, together with
25、 thecell and any extension leadwire, shall be designed to reduceerrors from the following sources:6.1.1 In highly conductive solutionsUncompensated elec-trode polarization due to excessive current density at theelectrode surfaces can cause negative conductivity errors.Insufficient series capacitance
26、 at the electrode/solution inter-face can allow charging effects to distort the a-c measurementand cause errors if not compensated. Leadwire resistance canadd significantly to the measured resistance.6.1.2 In low conductivity solutionsExcessive parallel ca-pacitance in the cell and extension leadwir
27、e can shunt themeasurement and cause positive conductivity errors. Tempera-ture compensation errors can be significant below 5 S/cm ifvariable coefficient algorithms are not employed as describedin Test Method D 5391.6.1.3 These sources of error are minimized by an appropri-ate combination of a-c dr
28、ive voltage, wave shape, frequency,phase correction, wave sampling technique and temperaturecompensation designed in by the instrument manufacturer. Theinstrument manufacturers recommendations shall be followedin selecting the proper cell constant, leadwire size, and lengthand maintenance of the ele
29、ctrode surface condition for therange of measurement. Calibration may be in either conduc-tivity or resistivity units.6.1.4 When an output signal is required from an on-lineinstrument, it shall be electrically isolated from the cell drive4The boldface numbers in parentheses refer to the list of refe
30、rences at the end ofthese test methods.TABLE 1 Electrical Conductivity Values Assigned to the Potassium Chloride in the Reference SolutionAReferenceSolutionApproximateNormality ofSolutionMethod of PreparationTempera-ture, CElectricalConductivity,S/cmA 1 74.2460 g of KCl weighed in air per 1 L of 0 6
31、5 176solution at 20C 18 97 83825 111 342B 0.1 7.4365 g of KCl weighed in air per 1 L of 0 7 138solution at 20C 18 11 16725 12 856C 0.01 0.7440 g of KCl weighed in air per 1 L of 0 773.6solution at 20C 18 1 220.525 1 408.8D 0.001 Dilute 100 mL of Solution C to 1 L at 20C 0 77.69B18 127.54B25 146.93AE
32、xcluding the conductivity of the water used to prepare the solutions. (See 7.2 and Section 14.) These tabulated conductivity values are in international units. Whenusing measuring instruments calibrated in absolute units, multiply the tabular values by 0.999505.BFrom Glasstone (13).D 1125 95 (2005)2
33、circuit to prevent interaction between a solution ground at thecell and an external circuit ground.6.2 Cells:6.2.1 Flow-through or in-line cells shall be used for mea-suring conductivities lower than 10 S/cm (resistivities higherthan 100 000 ohm cm), to avoid contamination from theatmosphere. Howeve
34、r, samples with conductivity greater than10 S/cm may also be measured. In all other cases, pipet-typeor dip cells can also be used. Pipet or dip cells may be used tomeasure samples in the range of 1 to 10 S/cm if the sample isprotected by an inert gaseous layer of nitrogen or helium.6.2.2 A cell con
35、stant shall be chosen which will give amoderate cell resistance, matching the instrument manufactur-ers requirements for the range of measurement. For laboratorybridges, Table 2 provides conservative guidelines.6.2.3 Flow-through and in-line cells shall be mounted sothat continuous flow of the sampl
36、e through or past it ispossible. Flow rate should be maintained at a constant rateconsistent with the manufacturers recommendations for thecell being used, particularly at conductivities below 10 S/cm.The cell shall retain calibration under conditions of pressure,flow, and temperature change, and sh
37、all exclude the atmo-sphere and be constructed of corrosion resistant, chemicallyinert materials. The chamber or cell shall be equipped withmeans for accurate measurement of the temperature.6.2.4 Platinized cells shall not be used for measurement ofconductivities below 10 S/cm, except that a trace o
38、r flash ofplatinum black may be used on cells for measurements in therange of 0.1 to 10 S/cm (see 9.4). Because of the cost andfragility of platinum cells, it is common practice to usetitanium, monel, and graphite electrodes for measurementswith accuracies on the order of 1 %. Note that these electr
39、odesmay require special surface preparation. Titanium and monelelectrodes are especially suitable for high resistance solutionssuch as ultrapure water, but may introduce a small surfaceresistance which limits their accuracy when the measuredresistance is less than a few thousand ohms (1).6.2.5 It is
40、 recommended that cells intended for the measure-ment of conductivities below 10 S/cm be reserved exclusivelyfor such applications.6.3 Temperature Probes:6.3.1 For Temperature ControlThe measurement of tem-perature is necessary for control of a temperature bath, manualtemperature compensation, or au
41、tomatic temperature compen-sation, or all of these. Thermometers, thermistors, and resis-tance temperature detectors with accuracies of 60.1C orbetter are acceptable for this application. An ASTM precisionthermometer, Number 63C, as defined in Specification E1,isrecommended. The calibration of tempe
42、rature probes should bechecked periodically by comparison to a reference temperatureprobe whose calibration is traceable to the U.S. NationalInstitute of Science and Technology (formerly NBS) or equiva-lent.6.3.2 For Temperature CorrectionA thermometer accu-rate to 0.1C is acceptable for this applic
43、ation, when theinstrument is not provided with manual or automatic tempera-ture compensation. (See Section 11).7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Co
44、mmit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterU
45、nless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, Type I. In making up the potassiumchloride solutions for cell constant determinations, use water ofconductivity not greater than 1.5 S/cm. If necessary, stabilizeto the laborato
46、ry atmosphere by aspirating air through thewater from a fritted glass or stainless steel gas dispersion tube.The equilibrium point is reached when the conductivity re-mains constant but not greater than 1.5 S/cm. The equilibriumconductivity must be added to Table 1.7.3 Alcohol95 % ethyl alcohol. Alt
47、ernatively, use isopro-pyl alcohol or methyl alcohol.7.4 Aqua Regia (3 + 1)Mix 3 volumes of concentratedhydrochloric acid (HCl, sp gr 1.19) with 1 volume of concen-trated nitric acid (HNO3, sp gr 1.42). This reagent should beused immediately after its preparation.7.5 Ethyl Ether.7.6 Hydrochloric Aci
48、d (sp gr 1.19)Concentrated HCl.7.7 Hydrochloric Acid (1 + 1)Mix 1 volume of concen-trated HCl (sp gr 1.19) with 1 volume of water.7.8 Platinizing SolutionDissolve 1.5 g of chloroplatinicacid (H2PtCl66H2O) in 50 mLof water containing 0.0125 g oflead acetate (Pb(C2H3O2)2).7.9 Potassium Chloride (KCl)T
49、he assay of the potassiumchloride must be 100.06 0.1 %. This standardization grade ofKCl is available from NIST and from commercial sources. Dryat 150C for 2 h or until weight loss is less than 0.02 %; storein desiccator.7.10 Potassium Chloride Reference Solution ADissolve74.2460 g of KCl (weighed in air) in water and dilute to 1 L at20 6 2C in a Class A volumetric flask.7.11 Potassium Chloride Reference Solution BDissolve7.4365 g of KCl (weighed in air) in water and dilute to 1 L at20 6 2C in a Class A volumetric f
