Designation:D1125–95(Reapproved2005)An American National Standard Standard Test Methods for
Electrical Conductivity and Resistivity of Water1
This standard is issued under thefixed designation D1125;the number immediately following the designation indicates the year of
original adoption or,in the ca of revision,the year of last revision.A number in parenthes indicates the year of last reapproval.A
superscript epsilon(e)indicates an editorial change since the last revision or reapproval.
This standard has been approved for u by agencies of the Department of Defen.
1.Scope
1.1The test methods cover the determination of the electrical conductivity and resistivity of water.The following test methods are included:
Range Sections Test Method A—Field and Routine Laboratory10to20000012to18 Measurement of Static(Non-Flowing)
Samples
µS/cm
Test Method B—Continuous In-Line Measure5to20000019to23 mentµS/cm
潮汕汤河粉1.2The test methods have been tested in reagent water.It is the ur’s responsibility to ensure the validity of the test methods for waters of untested matrices.
1.3For measurements below the range of the test meth-ods,refer to Test Method D5391.
1.4This standard does not purport to address all of the safety concerns,if any,associated with its u.
It is the responsibility of the ur of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u.
2.Referenced Documents
2.1ASTM Standards:2
D1066Practice for Sampling Steam
D1129Terminology Relating to Water
D1192Specification for Equipment for Sampling Water and Steam in Clod Conduits3
D1193Specification for Reagent Water
D2186Test Method for Deposit-Forming Impurities in Steam
D2777Practice for Determination of Precision and Bias of Applicable Methods of Committee D19on Water
D3370Practices for Sampling Water from Clod Conduits
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因为爱情的歌词D4519Test Method for On-Line Determination of Anions and Carbon Dioxide in High Purity Water by Cation Exchange and Degasd Cation Conductivity
D5391Test Method for Electrical Conductivity and Resis-tivity of a Flowing High Purity Water Sample电气自动化技术
E1Specification for ASTM Liquid-in-Glass Thermometers
3.Terminology
3.1Definitions:
3.1.1electrical conductivity—the reciprocal of the a-c re-sistance in ohms measured between opposite faces of a centimetre cube of an aqueous solution at a specified tempera-ture.
N OTE1—The unit of electrical conductivity is siemens per centimetre. (The previously ud units of mhos/cm are numerically equivalent to S/cm.)The actual resistance of the cell,R
x
,is measured in ohms.The
conductance,1/R
x
,is directly proportional to the cross-ctional area,A (in cm2),and inverly proportional to the length of the path,L(in cm):
1/R x5K·A/L
The conductance measured between opposite faces of a centimetre cube,K,is called conductivity.Conductivity values are usually expresd in microsiemens/centimetre or in siemens/centimetre at a specified temperature,normally25°C.
3.1.2electrical resistivity—the a-c resistance in ohms mea-sured between opposite faces of a centimetre cube of an aqueous solution at a specified temperature.
N OTE2—The unit of electrical resistivity is ohm-centimetre.The actual
resistance of the cell,R
x
,is measured in ohms,and is directly proportional to the length of the path,L(in cm),and inverly proportional to the cross-ctional area,A(in cm2):
R x5R·L/A
The resistance measured between opposite faces of a centi-metre cube,R,is called resistivity.Resistivity values are usually expresd in ohm·centimetre,or in megohm·centime-tre,at a specified temperature,normally25°C.
3.1.3For definitions of other terms ud in the methods, refer to Terminology D1129.
3.2Symbols:Symbols:
3.2.1Symbols ud in the equations in Sections14and16 are defined as follows:
J=cell constant,cm−1,
K=conductivity at25°C,µS/cm,
1The test methods are under the jurisdiction of Committee D19on Water and
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are the direct responsibility of Subcommittee D19.03on Sampling of Water and
Water-Formed Deposits,Surveillance of Water,and Flow Measurement of Water.
Current edition approved April1,2005.Published April2005.Originally
approved in1950.Last previous edition approved in1999as D1125–95(1999).
2For referenced ASTM standards,visit the ASTM website,www.astm,or
contact ASTM Customer Service at rvice@astm.For Annual Book of ASTM
Standards volume information,refer to the standard’s Document Summary page on
the ASTM website.
3Withdrawn.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States. --``,`,,``,`,,,,`,,,`,,`,```,``-`-`,,`,,`,`,,`---
K x =measured conductance,S,
K 1=conductivity of the KCl in the reference solution at the temperature of measurement (Table 1),µS/cm,
K 2=conductivity of the water ud to prepare the reference solution,at the same temperature of measurement,µS/cm,Q =temperature correction factor (e Section 11),R =resistivity at 25°C,ohm ·cm,R x =measured resistance,ohm.
4.Significance and U
4.1The test methods are applicable for such purpos as impurity detection and,in some cas,the quantitative mea-surement of ionic constituents dissolved in waters.The include dissolved electrolytes in natural and treated waters,such as boiler water,boiler feedwater,cooling water,and saline and brackish water.
4.1.1Their concentration may range from trace levels in pure waters (1)4to significant levels in condend steam (e Test Methods D 2186and D 4519,and Ref (2)),or pure salt solutions.
4.1.2Where the principal interest in the u of conductivity methods is to determine steam purity,e Ref (3).The test methods may also be ud for checking the correctness of water analys (4).
5.Interferences
5.1Exposure of a sample to the atmosphere may cau changes in conductivity/resistivity,due to loss or gain of dissolved gas.This is extremely important in the ca of very pure waters with low concentrations of dissolved ionized materials.The carbon dioxide,normally prent in the air,can drastically increa the conductivity of pure waters by approxi-mately 1µS/cm.Contact with air should be avoided by using flow-through or in-line cell where feasible.Chemically pure inert gas,such as nitrogen or helium,may be ud to blanket the surface of samples.
5.2Undissolved or slowly precipitating materials in the sample can form a coating on the electrodes of the conductivity
cell that may cau erroneous readings.For example,biofoul-ing of the cell or a build-up of filming amines may cau poor cell respon.In most cas the problems can be eliminated by washing the cells with appropriate solvents.
5.3If an unshielded cell is ud to measure the resistivity/conductivity of high resistivity water there is a possibility of electrical pickup causing erroneous reading.For this reason it is recommended that conductivity cells for this application be of coaxial shielded type or equivalent,and that the cables an
d instrument also be shielded.
6.Apparatus
6.1Measuring Circuit —The instrument may be a manually operated wheatstone bridge or the equivalent,or a direct reading analog or digital meter.Instruments shall energize the conductivity cell with alternating current and,together with the cell and any extension leadwire,shall be designed to reduce errors from the following sources:
6.1.1In highly conductive solutions —Uncompensated elec-trode polarization due to excessive current density at the electrode surfaces can cau negative conductivity errors.Insufficient ries capacitance at the electrode/solution inter-face can allow charging effects to distort the a-c measurement and cau errors if not compensated.Leadwire resistance can add significantly to the measured resistance.
6.1.2In low conductivity solutions —Excessive parallel ca-pacitance in the cell and extension leadwire can shunt the measurement and cau positive conductivity errors.Tempera-ture compensation errors can be significant below 5µS/cm if variable coefficient algorithms are not employed as described in Test Method D 5391.
6.1.3The sources of error are minimized by an appropri-ate combination of a-c drive voltage,wave shape,frequency,pha correction,wave sampling technique and temperature compensation designed in by the instrument manufacturer.The instrument manufacturer’s recommendations shall be followed in lecting the proper cell constant,leadwire size,and length and maintenance of the electrode surface condition for the range of measurement.Calibration may be in either conduc-tivity or resistivity units.
6.1.4When an output signal is required from an on-line instrument,it shall be electrically isolated from the cell drive
4
The boldface numbers in parenthes refer to the list of references at the end of the test methods.长平大战
TABLE 1Electrical Conductivity Values Assigned to the Potassium Chloride in the Reference Solution A
Reference Solution女警察简笔画
Approximate Normality of Solution
Method of Preparation
Tempera-ture,°C
Electrical Conductivity,µS/cm A
1猪肝汤的家常做法
74.2460g of KCl weighed in air per 1L of
065176solution at 20°C 189783825111342B 0.1
7.4365g of KCl weighed in air per 1L of
07138solution at 20°C 18111672512856C 0.01
0.7440g of KCl weighed in air per 1L of
0773.6solution at 20°C 181220.5251408.8D 0.001
Dilute 100mL of Solution C to 1L at 20°C
077.69B 18127.54B 25
146.93
A
Excluding the conductivity of the water ud to prepare the solutions.(See 7.2and Section 14.)The tabulated conductivity values are in international units.When using measuring instruments calibrated in absolute units,multiply the tabular values by 0.999505.B
From Glasstone (13)
.
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circuit to prevent interaction between a solution ground at the cell and an external circuit ground.6.2Cells :
6.2.1Flow-through or in-line cells shall be ud for mea-suring conductivities lower than 10µS/cm (resistivities higher than 100000ohm ·cm),to avoid contamination from the atmosphere.However,samples with conductivity greater than 10µS/cm may also be measured.In all other cas,pipet-type or dip cells can also be ud.Pipet or dip cells may be ud to measure samples in the range of 1to 10µS/cm if the sample is protected by an inert gaous layer of nitrogen or helium.6.2.2A cell constant shall be chon which will give a moderate cell resistance,matching the instrument manufactur-er’s requirements for the range of measurement.For laboratory bridges,Table 2provides conrvative guidelines.
6.2.3Flow-through and in-line cells shall be mounted so that continuous flow of the sample through or past it is possible.Flow rate should be maintained at a constant rate consistent with the manufacturer’s recommendations for the cell being ud,particularly at conductivities below 10µS/cm.The cell shall retain calibration under conditions of pressure,flow,and temperature change,and shall exclude the atmo-sphere and be constructed of corrosion resistant,chemically inert materials.The chamber or cell shall be equipped with means for accurate measurement of the temperature.
6.2.4Platinized cells shall not be ud for measurement of conductivities below 10µS/cm,except that
a trace or flash of platinum black may be ud on cells for measurements in the range of 0.1to 10µS/cm (e 9.4).Becau of the cost and fragility of platinum cells,it is common practice to u titanium,monel,and graphite electrodes for measurements with accuracies on the order of 1%.Note that the electrodes may require special surface preparation.Titanium and monel electrodes are especially suitable for high resistance solutions such as ultrapure water,but may introduce a small surface resistance which limits their accuracy when the measured resistance is less than a few thousand ohms (1).
6.2.5It is recommended that cells intended for the measure-ment of conductivities below 10µS/cm be rerved exclusively for such applications.
6.3Temperature Probes :
6.3.1For Temperature Control —The measurement of tem-perature is necessary for control of a temperature bath,manual temperature compensation,or automatic temperature compen-sation,or all of the.Thermometers,thermistors,and resis-tance temperature detectors with accuracies of 60.1°C or better are acceptable for this application.An ASTM precision thermometer,Number 63C,as defined in Specification E 1,is recommended.The calibration of temperature probes should be checked periodically by comparison to a reference temperature
probe who calibration is traceable to the U.S.National Institute of Science and Technology (formerly NBS)or equiva-lent.
6.3.2For Temperature Correction —A thermometer accu-rate to 0.1°C is acceptable for this application,when the instrument is not provided with manual or automatic tempera-ture compensation.(See Section 11).
7.Reagents
7.1Purity of Reagents —Reagent grade chemicals shall be ud in all tests.Unless otherwi indicated,it is intended that all reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may be ud,provided it is first ascertained that the reagent is of sufficiently high purity to permit its u without lesning the accuracy of the determination.
7.2Purity of Water —Unless otherwi indicated,references to water shall be understood to mean reagent water conforming to Specification D 1193,Type I.In making up the potassium chloride solutions for cell constant determinations,u water of conductivity not greater than 1.5µS/cm.If necessary,stabilize to the laboratory atmosphere by aspirating air through the water from a fritted gla
ss or stainless steel gas dispersion tube.The equilibrium point is reached when the conductivity re-mains constant but not greater than 1.5µS/cm.The equilibrium conductivity must be added to Table 1.
7.3Alcohol —95%ethyl alcohol.Alternatively,u isopro-pyl alcohol or methyl alcohol.
7.4Aqua Regia (3+1)—Mix 3volumes of concentrated hydrochloric acid (HCl,sp gr 1.19)with 1volume of concen-trated nitric acid (HNO 3,sp gr 1.42).This reagent should be ud immediately after its preparation.7.5Ethyl Ether .
7.6Hydrochloric Acid (sp gr 1.19)—Concentrated HCl.7.7Hydrochloric Acid (1+1)—Mix 1volume of concen-trated HCl (sp gr 1.19)with 1volume of water.
7.8Platinizing Solution —Dissolve 1.5g of chloroplatinic acid (H 2PtCl 6·6H 2O)in 50mL of water containing 0.0125g of lead acetate (Pb(C 2H 3O 2)2).
7.9Potassium Chloride (KCl)—The assay of the potassium chloride must be 100.060.1%.This standardization grade of KCl is available from NIST and from commercial sources.Dry at 150°C for 2h or until weight loss is less than 0.02%;store in desiccator.
7.10Potassium Chloride Reference Solution A —Dissolve 74.2460g of KCl (weighed in air)in water and dilute to 1L at 2062°C in a Class A volumetric flask.
7.11Potassium Chloride Reference Solution B —Dissolve 7.4365g of KCl (weighed in air)in water and dilute to 1L at 2062°C in a Class A volumetric flask.
5
Reagent Chemicals,American Chemical Society Specifications ,American Chemical Society,Washington,DC.For suggestions on the testing of reagents not listed by the American Chemical Society,e Analar Standards for Laboratory Chemicals ,BDH Ltd.,Poole,Dort,U.K.,and the United States Pharmacopeia and National Formulary ,U.S.Pharmaceutical Convention,Inc.(USPC),Rockville,MD.
TABLE 2Recommended Cell Constants for Various Conductivity
Ranges
Range of Conductivity,µS/cm
Cell Constant,cm −1
0.05to 100.01to 0.110to 2000.1to 1200to 5000
1to 105000to 1000000
10to
100
7.12Potassium Chloride Reference Solution C—Dissolve 0.7440g of KCl(weighed in air)in water and to dilute1L at 2062°C in a Class A volumetricflask.
7.13Potassium Chloride Reference Solution D—Dilute100 mL of reference solution C to1L with water at2062°C in a Class A volumetricflask shortly before using.Store the solution in a glass-stoppered bottle of chemically resistant glass which has only been ud for storage of this solution. N OTE3—The electrical conductivity of each of the referenced solutions is given in Table1.The values for electrical conductivities for the solutions are tho of G.Jones and B.C.Bradshaw(5),confir
med in1987 (6)and1989(7)by the National Institute of Standards and Technology (NIST).The data of T.Shedlovsky(8)are ud for Solution D.Solutions A,B,and C were prepared by Jones and Bradshaw using the molal or demal basis by dissolving71.1352,7.4191,and0.7453g,respectively,of KCl(in vacuum)per1000g of solution(in vacuum).The method of preparation given in Table1includes the corrections to weights of KCl(in air against brass weights)per litre of solutions at20°C and assumes the density of KCl=1.98,density of brass=8.4,and the density of air=0.00118.The densities of1.0N,0.10N,and0.010N KCl at20°C, 1.04420,1.00280,and0.99871g/mL,respectively,were interpolated from the data in the International Critical Tables(9).
8.Sampling
8.1Samples shall be collected in accordance with Practice D1066,Specification D1192,and Practices D3370,as appli-cable.
8.2Avoid exposure of the sample to atmospheres containing ammonia or acidic gas.Protect the sample to avoid gain or loss of dissolved gas,particularly if there is some delay before the conductivity measurements are made.Preferably, u aflow-type cell for sampling and measuring condend steam or water having a conductivity of less than10µS/cm. For waters in the range of5to
10µS/cm,a dip-type cell may be ud if a layer of chemically pure nitrogen or helium is maintained over the surface.
9.Preparation of Electrodes
9.1If the cell constant as checked does not fall within reasonable limits of its nominal value,it is necessary to clean or replatinize the electrodes or replace the cell.In general,no mechanical cleaning should be attempted.In high purity water measurements,where the prence offinely divided platinum is undesirable due to its long retention of impurities,platini-zation of electrodes should be omitted,especially for testing of water having a conductivity below10µS/cm(e9.4).On the other hand,clean and well-platinized electrodes are increas-ingly important in testing water of higher conductivities, particularly above1000µS/cm.
9.2The cell manufacturer’s instructions may be followed for cleaning the electrodes as well as other parts of the cell.A suitable cleaning solution consists of a mixture of1part by volume of isopropyl alcohol,1part of ethyl ether,(with polymer cells,check compatibility)and1part of HCl(1+1). After cleaning,thoroughlyflush the cell with water.If the old platinum black coating is to be removed,judicious application of aqua regia to the electrodes,or electrolysis in HCl(sp gr 1.19)is frequently successful.
9.3Platinize the electrodes of the cell with H2PtCl6solu-tion.A suitable plating apparatus consists of a6volt a-c supply,a variable resistor,milliammeter,and an electrode.The deposit should prent a black,velvety appearance and should adhere well to the electrode surface.The procedure for platinizing is not critical.Follow the manufacturer’s instructions or the following guidelines.Good platinized coatings are obtained using from 1.5to3coulombs/cm2of electrode area.For example,for an electrode having a total area(both sides)of10 cm2,the plating time at a current of20mA would be from121⁄2 to25min.The current density may be from1to4mA/cm2of electrode area.Plate the electrodes one at a time with the aid of an extra electrode.During the plating,agitate the solution gently,or u ultrasonic bath.When not in u,platinized cells should befilled with water to prevent the drying out of electrodes while in storage.
9.4For measurement of conductivities in the range of0.1to 10µS/cm,a trace orflash coating of platinum black may be ud.For aflash coating,the cell is left in the platinic chloride solution for only2or3s at a current of about20mA.Aflash coating will leave the electrodes with their metallic appear-ance,but with a faint blackish tint.
10.Calibration
10.1Measuring Instrument—A calibrating resistor to be ud in place of the conductivity cell may be furnished by the manufacturer,together with information as to the correct scale reading the instrument shall assume when this resistor is connected in place of the conductivity cell.Follow the manu-facturer’s instructions and periodically check the instrument. Alternatively,standard resistors with certified accuracy of 60.05%may be ud with appropriate calculations adapted to the instrument scale.Some instruments may be factory cali-brated,taking into account the resistance of the cable wire attached to the conductivity cell;this may be indicated by a warning to avoid cutting or extending the cable length.When lead wires between the instrument and the cell are long,check the installation at least once by connecting the calibrating resistor at the far end of the lead wire and noting the difference, if any,in reading with the long lead wire in the circuit.Check portable or manually operated instruments in a similar manner with one or veral calibrating resistors.Note errors of signifi-cant magnitude and correct subquent conductivity readings. Calibration checks should be made at values as clo as possible to the conductivity values expected in samples.This is especially important if the measurement is made at the extreme high or low end of an instrument’s range.Instruments sub-jected tofield u may require more frequent checks of calibration.For direct reading instruments,the conductivity check resistance in ohms equals the cell constant(cm−1) divided by the conductivity desired(S/cm)while the resistivity check resistance equals cell constant(cm−1)times the resis-tivity desired(ohm·cm).
10.2Conductivity Cells—Forfield and routine laboratory testing,the calibration of conductivity cells may be checked by comparing instrument readings taken with the cell in question against readings on the same sample or ries of samples taken with a conductivity cell of known or certified cell constant. Exerci care to ensure that both working and reference cells are at the same temperature or,alternatively,at different but known temperatures so that a correction as later described
can --``,`,,``,`,,,,`,,,`,,`,```,``-`-`,,`,,`,`,,`---
be applied.Resistivity-reading instruments will indicate in direct proportion to the cell constant,while conductivity reading instruments will indicate in inver proportion to cell constant.Conductivity cells may be calibrated with reference solutions in accordance with Section14.
11.Temperature Coefficient of Conductivity/Resistivity 11.1The conductivity/resistivity of water and aqueous so-lutions depends strongly upon the temperature.(See Table3.) The normal practice is to report conductivity and resistivity values referenced to25.0°C.The coefficient varies depending upon
the nature and composition of the dissolved electrolytes, and upon the concentration.The dissociation of water contrib-utes significantly to conductivities at5µS/cm or less and increas the temperature coefficient from near2%per°C at above5µS/cm to near5%per°C at0.055µS/cm.To avoid making a correction,it is necessary to hold the temperature of the sample to2560.1°C.If this cannot be done,the temperature coefficient must be determined and a correction applied.This requires a ries of conductivity and temperature measurements on the sample over the required temperature range.Where automatic temperature compensation is ud,the temperature compensation algorithm should be chon that best simulates the composition of the samples to be tested.In high purity water,5µS/cm or less,the variable coefficient shall be automatically determined and applied across the range of measurement for both the dissociation of water and its inter-action with salt or other contaminations.(See Test Method D5391and Refs(10),(11),and(12)for more information.)
11.2In static systems,exerci care to avoid change of composition caud by loss of volatile constituents or by pick-up of contaminants from the air to the containing vesl during the ries of measurements.
11.3Inflowing systems,provide means for variable heating or cooling so that the desired range of temperature will be covered.Regulate the rate offlow through each cell so as to keep the cell adequa
telyflushed.
11.4From the data obtained,plot conductivity against temperature.Make sure that the conductivity readings are uncompensated.From the curve a table of temperature correc-tion factors may be prepared,or the ratio of conductivity at temperature T to conductivity at25°C may be plotted against temperature T,and this ratio or correction factor,Q,taken from the smoothed curve.
N OTE4—Depending on the type of compensation ud,uncompensated readings may be obtained by tting temperature to25°C,by putting the temperature probe in a25°C bath,or by substituting an electrical resistance equivalent to25°C.
11.5When using an instrument provided with a manual or automatic temperature compensator,follow the manufacturer’s instructions to calibrate the compensator or check its accuracy and applicability to the sample being tested.
TEST METHOD A—FIELD AND ROUTINE LABORATORY MEASUREMENT OF STATIC(NON-
FLOWING)SAMPLES
12.Scope
12.1This test method is applicable tofield and routine laboratory measurements of the electrical conductivity of water using static samples.
13.Summary of Test Method
13.1This test method utilizes dip-type or pipet-type con-ductivity cells for testing static samples having conductivities greater than10µS/cm.Temperature control and correction methods are also provided.
14.Determination of Cell Constant
14.1For the purpos of this test method,the cell constant of the conductivity cell ud shall be known within61%.The manufacturer’s certification of the cell constant within this accuracy is generally considered satisfactory but the ur is advid that damage could occur in shipment and it is best to recheck the cell constant when received.If the conductivity cell has been in rvice for a period subquent to this certification,it shall be rechecked by the manufacturer,or in the laboratory.
14.2Rin the conductivity cell veral times with water, then at least twice with the KCl reference solution that has a conductivity nearest to that of the sample under test(Table1). Control the solution
temperature to2560.1°C.Measure the resistance of the cell.Repeat the measurement on additional portions of the KCl reference solution until the value obtained remains constant to within the limits of precision in accordance with Section18.
14.3For instruments reading measured resistance in ohms, calculate the cell constant:
J51026·R x~K11K2!
14.4For instruments reading measured conductance in Si-emens,calculate the cell constant:
J51026·~K11K2!/K x
N OTE5—Since the conductivities of a mixture of two solutions are not exactly additive,the u of K
1
+K
2
is only an approximation and requires
TABLE3Conductivity Values of Pure Water and Increas Due
to Sodium Chloride A
From Thornton(1).
