ASTM D1125-95(1999)

Standard Test Methods for Electrical Conductivity and Resistivity of Water

SCOPE
1.1 These 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 Laboratory 10 to 200 000 12 to 18 Measurement of Static (Non-Flowing) Samples

General Information

• Status: Historical
• Publication Date: 09-Jun-1999
• ICS: 13.060.60 - Examination of physical properties of water
• Technical Committee: D19 - Water
• Drafting Committee: D19.03 - Sampling Water and Water-Formed Deposits, Analysis of Water for Power Generation and Process Use, On-Line Water Analysis, and Surveillance of Water

Relations

• Replaced By: ASTM D1125-95(2005) - Standard Test Methods for Electrical Conductivity and Resistivity of Water
• Effective Date: 01-Apr-2005
• Referred By: ASTM C225-85(2022) - Standard Test Methods for Resistance of Glass Containers to Chemical Attack
• Effective Date: 10-Jun-1999
• Referred By: ASTM D1755-21 - Standard Specification for Poly(Vinyl Chloride) Resins
• Effective Date: 10-Jun-1999
• Referred By: ASTM D4266-17 - Standard Test Methods for Precoat Capacity of Powdered Ion-Exchange Resins
• Effective Date: 10-Jun-1999
• Referred By: ASTM D7513-17 - Standard Test Method for Capacity of Mixed Bed Ion Exchange Cartridges
• Effective Date: 10-Jun-1999
• Referred By: ASTM D5012-20 - Standard Practice for Preparation of Materials Used for the Collection and Preservation of Atmospheric Wet Deposition
• Effective Date: 10-Jun-1999
• Referred By: ASTM D7285-06(2017) - Standard Guide for Recordkeeping Microfiltration and Ultrafiltration Systems
• Effective Date: 10-Jun-1999
• Referred By: ASTM D2651-01(2016) - Standard Guide for Preparation of Metal Surfaces for Adhesive Bonding
• Effective Date: 10-Jun-1999
• Referred By: ASTM D4194-23 - Standard Test Methods for Operating Characteristics of Reverse Osmosis and Nanofiltration Devices
• Effective Date: 10-Jun-1999
• Referred By: ASTM D4399-05(2023) - Standard Test Method for Measuring Electrical Conductivity of Electrocoat Baths
• Effective Date: 10-Jun-1999
• Referred By: ASTM D5391-23 - Standard Test Method for Electrical Conductivity and Resistivity of a Flowing High Purity Water Sample
• Effective Date: 10-Jun-1999
• Referred By: ASTM D6807-17 - Standard Test Method for Operating Performance of Continuous Electrodeionization Systems on Reverse Osmosis Permeates from<brk/>2 to 100 &#x3bc;S/cm
• Effective Date: 10-Jun-1999
• Referred By: ASTM D5615-21 - Standard Practice for Operating Characteristics of Home Reverse Osmosis Devices
• Effective Date: 10-Jun-1999
• Referred By: ASTM D3375-18 - Standard Test Method for Column Capacity of Particulate Mixed Bed Ion<brk/>Exchange Materials
• Effective Date: 10-Jun-1999
• Referred By: ASTM G96-90(2018) - Standard Guide for Online Monitoring of Corrosion in Plant Equipment (Electrical and Electrochemical Methods)
• Effective Date: 10-Jun-1999

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
Designation:D 1125–95 (Reapproved 1999)
Standard Test Methods for
Electrical Conductivity and Resistivity of Water
This standard is issued under the fixed designation D 1125; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses 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 use by agencies of the Department of Defense.
1. Scope Exchange and Degassed Cation Conductivity
D5391 Test Method for Electrical Conductivity and Resis-
1.1 These test methods cover the determination of the
tivity of a Flowing High Purity Water Sample
electrical conductivity and resistivity of water. The following
E1 Specification for ASTM Thermometers
test methods are included:
Range Sections
3. Terminology
Test Method A—Field and Routine Laboratory 10 to 200 000 12 to 18
Measurement of Static (Non-Flowing) µS/cm
3.1 Definitions:
Samples
3.1.1 electrical conductivity—the reciprocal of the a-c re-
Test Method B—Continuous In-Line Measure 5 to 200 000 19 to 23
sistance in ohms measured between opposite faces of a
ment µ S/cm
centimetre cube of an aqueous solution at a specified tempera-
1.2 These test methods have been tested in reagent water. It
ture.
is the user’s responsibility to ensure the validity of these test
methods for waters of untested matrices. NOTE 1—The unit of electrical conductivity is siemens per centimetre.
(The previously used units of mhos/cm are numerically equivalent to
1.3 For measurements below the range of these test meth-
S/cm.) The actual resistance of the cell, R , is measured in ohms. The
x
ods, refer to Test Method D5391.
conductance, 1/R , is directly proportional to the cross-sectional area, A
x
1.4 This standard does not purport to address all of the
(in cm ), and inversely proportional to the length of the path, L (in cm):
safety concerns, if any, associated with its use. It is the
1/R 5 K·A/L
x
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- The conductance measured between opposite faces of a
centimetre cube, K, is called conductivity. Conductivity values
bility of regulatory limitations prior to use.
are usually expressed in microsiemens/centimetre or in
2. Referenced Documents
siemens/centimetre at a specified temperature, normally 25°C.
3.1.2 electrical resistivity—the a-c resistance in ohms mea-
2.1 ASTM Standards:
D1066 Practice for Sampling Steam sured between opposite faces of a centimetre cube of an
aqueous solution at a specified temperature.
D1129 Terminology Relating to Water
D1192 Specification for Equipment for Sampling Water
NOTE 2—Theunitofelectricalresistivityisohm-centimetre.Theactual
and Steam in Closed Conduits
resistanceofthecell, R ,ismeasuredinohms,andisdirectlyproportional
x
D1193 Specification for Reagent Water
to the length of the path, L (in cm), and inversely proportional to the
D2186 Test Method for Deposit-Forming Impurities in
cross-sectional area, A (in cm ):
Steam
R 5 R·L/A
x
D2777 Practice for Determination of Precision and Bias of
The resistance measured between opposite faces of a centi-
Applicable Methods of Committee D-19 on Water
metre cube, R, is called resistivity. Resistivity values are
D3370 Practices for Sampling Water from Closed Con-
usually expressed in ohm·centimetre, or in megohm · centime-
duits
tre, at a specified temperature, normally 25°C.
D4519 Test Method for On-Line Determination of Anions
3.1.3 For definitions of other terms used in these methods,
and Carbon Dioxide in High Purity Water by Cation
refer to Terminology D1129.
3.2 Symbols:Symbols:
3.2.1 Symbols used in the equations in Sections 14 and 16
These test methods are under the jurisdiction of Committee D19 on Water and
are defined as follows:
−1
are the direct responsibility of Subcommittee D19.03 on Sampling of Water and
J =cell constant, cm ,
Water-Formed Deposits, Surveillance of Water, and Flow Measurement of Water.
Current edition approved Oct. 10, 1995. Published December 1995. Originally
published as D1125–50 T. Last previous edition D1125–91.
Annual Book of ASTM Standards, Vol 11.01.
3 4
Annual Book of ASTM Standards, Vol 11.02. Annual Book of ASTM Standards, Vol 14.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 1125–95 (1999)
A
TABLE 1 Electrical Conductivity Values Assigned to the Potassium Chloride in the Reference Solution
Approximate Electrical
Reference Tempera-
Normality of Method of Preparation Conductivity,
Solution ture, °C
Solution µS/cm
A 1 74.2460 g of KCl weighed in air per 1 L of 0 65 176
solution at 20°C 18 97 838
25 111 342
B 0.1 7.4365 g of KCl weighed in air per 1 L of 0 7 138
solution at 20°C 18 11 167
25 12 856
C 0.01 0.7440 g of KCl weighed in air per 1 L of 0 773.6
solution at 20°C 18 1 220.5
25 1 408.8
B
D 0.001 Dilute 100 mL of Solution C to 1 L at 20°C 0 77.69
B
18 127.54
25 146.93
A
Excluding the conductivity of the water used to prepare the solutions. (See 7.2 and Section 14.) These 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).
K =conductivity at 25°C, µS/cm, 5.2 Undissolved or slowly precipitating materials in the
K =measured conductance, S, samplecanformacoatingontheelectrodesoftheconductivity
x
K =conductivity of the KCl in the reference solution at the
cell that may cause erroneous readings. For example, biofoul-
temperature of measurement (Table 1), µS/cm,
ing of the cell or a build-up of filming amines may cause poor
K =conductivity of the water used to prepare the reference
cell response. In most cases these problems can be eliminated
solution, at the same temperature of measurement, µS/cm,
by washing the cells with appropriate solvents.
Q =temperature correction factor (see Section 11),
5.3 If an unshielded cell is used to measure the resistivity/
R =resistivity at 25°C, ohm · cm,
conductivity of high resistivity water there is a possibility of
R =measured resistance, ohm.
x
electrical pickup causing erroneous reading. For this reason it
is recommended that conductivity cells for this application be
4. Significance and Use
of coaxial shielded type or equivalent, and that the cables and
4.1 These test methods are applicable for such purposes as
instrument also be shielded.
impurity detection and, in some cases, the quantitative mea-
surement of ionic constituents dissolved in waters. These
6. Apparatus
include dissolved electrolytes in natural and treated waters,
6.1 Measuring Circuit—The instrument may be a manually
suchasboilerwater,boilerfeedwater,coolingwater,andsaline
operated wheatstone bridge or the equivalent, or a direct
and brackish water.
reading analog or digital meter. Instruments shall energize the
4.1.1 Their concentration may range from trace levels in
conductivitycellwithalternatingcurrentand,togetherwiththe
pure waters (1) to significant levels in condensed steam (see
cell and any extension leadwire, shall be designed to reduce
Test Methods D2186 and D4519, and Ref (2)), or pure salt
errors from the following sources:
solutions.
6.1.1 In highly conductive solutions—Uncompensated elec-
4.1.2 Where the principal interest in the use of conductivity
trode polarization due to excessive current density at the
methods is to determine steam purity, see Ref (3). These test
electrode surfaces can cause negative conductivity errors.
methods may also be used for checking the correctness of
Insufficient series capacitance at the electrode/solution inter-
water analyses (4).
face can allow charging effects to distort the a-c measurement
5. Interferences and cause errors if not compensated. Leadwire resistance can
add significantly to the measured resistance.
5.1 Exposure of a sample to the atmosphere may cause
6.1.2 In low conductivity solutions—Excessive parallel ca-
changes in conductivity/resistivity, due to loss or gain of
pacitance in the cell and extension leadwire can shunt the
dissolvedgases.Thisisextremelyimportantinthecaseofvery
measurement and cause positive conductivity errors. Tempera-
pure waters with low concentrations of dissolved ionized
ture compensation errors can be significant below 5 µS/cm if
materials. The carbon dioxide, normally present in the air, can
variable coefficient algorithms are not employed as described
drasticallyincreasetheconductivityofpurewatersbyapproxi-
in Test Method D5391.
mately 1 µS/cm. Contact with air should be avoided by using
flow-through or in-line cell where feasible. Chemically pure
6.1.3 These sources of error are minimized by an appropri-
inert gases, such as nitrogen or helium, may be used to blanket
ate combination of a-c drive voltage, wave shape, frequency,
the surface of samples.
phase correction, wave sampling technique and temperature
compensationdesignedinbytheinstrumentmanufacturer.The
instrument manufacturer’s recommendations shall be followed
5 in selecting the proper cell constant, leadwire size, and length
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
these test methods. and maintenance of the electrode surface condition for the
D 1125–95 (1999)
TABLE 2 Recommended Cell Constants for Various Conductivity
better are acceptable for this application. An ASTM precision
Ranges
thermometer, Number 63C, as defined in Specification E1, is
−1
Range of Conductivity, µS/cm Cell Constant, cm
recommended.Thecalibrationoftemperatureprobesshouldbe
0.05 to 10 0.01 to 0.1
checkedperiodicallybycomparisontoareferencetemperature
10 to 200 0.1 to 1
probe whose calibration is traceable to the U.S. National
200 to 5000 1 to 10
InstituteofScienceandTechnology(formerlyNBS)orequiva-
5000 to 1 000 000 10 to 100
lent.
6.3.2 For Temperature Correction—A thermometer accu-
rate to 0.1°C is acceptable for this application, when the
range of measurement. Calibration may be in either conduc-
instrument is not provided with manual or automatic tempera-
tivity or resistivity units.
ture compensation. (See Section 11).
6.1.4 When an output signal is required from an on-line
7. Reagents
instrument, it shall be electrically isolated from the cell drive
circuit to prevent interaction between a solution ground at the
7.1 Purity of Reagents—Reagent grade chemicals shall be
cell and an external circuit ground.
used in all tests. Unless otherwise indicated, it is intended that
6.2 Cells:
all reagents shall conform to the specifications of the Commit-
6.2.1 Flow-through or in-line cells shall be used for mea-
tee onAnalytical Reagents of theAmerican Chemical Society,
suring conductivities lower than 10 µS/cm (resistivities higher
where such specifications are available. Other grades may be
than 100000 ohm · cm), to avoid contamination from the
used, provided it is first ascertained that the reagent is of
atmosphere. However, samples with conductivity greater than
sufficiently high purity to permit its use without lessening the
10 µS/cm may also be measured. In all other cases, pipet-type
accuracy of the determination.
or dip cells can also be used. Pipet or dip cells may be used to
7.2 Purity of Water—Unlessotherwiseindicated,references
measure samples in the range of 1 to 10 µS/cm if the sample is
towatershallbeunderstoodtomeanreagentwaterconforming
protected by an inert gaseous layer of nitrogen or helium.
to Specification D1193, Type I. In making up the potassium
6.2.2 A cell constant shall be chosen which will give a
chloridesolutionsforcellconstantdeterminations,usewaterof
moderate cell resistance, matching the instrument manufactur-
conductivity not greater than 1.5 µS/cm. If necessary, stabilize
er’srequirementsfortherangeofmeasurement.Forlaboratory
to the laboratory atmosphere by aspirating air through the
bridges, Table 2 provides conservative guidelines.
water from a fritted glass or stainless steel gas dispersion tube.
6.2.3 Flow-through and in-line cells shall be mounted so
The equilibrium point is reached when the conductivity re-
that continuous flow of the sample through or past it is
mainsconstantbutnotgreaterthan1.5µS/cm.Theequilibrium
possible. Flow rate should be maintained at a constant rate
conductivity must be added to Table 1.
consistent with the manufacturer’s recommendations for the
7.3 Alcohol—95% ethyl alcohol.Alternatively, use isopro-
cell being used, particularly at conductivities below 10 µS/cm.
pyl alcohol or methyl alcohol.
The cell shall retain calibration under conditions of pressure,
7.4 Aqua Regia (3+1)—Mix 3 volumes of concentrated
flow, and temperature change, and shall exclude the atmo-
hydrochloric acid (HCl, sp gr 1.19) with 1 volume of concen-
sphere and be constructed of corrosion resistant, chemically
trated nitric acid (HNO , sp gr 1.42). This reagent should be
inert materials. The chamber or cell shall be equipped with
used immediately after its preparation.
means for accurate measurement of the temperature.
7.5 Ethyl Ether.
6.2.4 Platinized cells shall not be used for measurement of
7.6 Hydrochloric Acid (sp gr 1.19)—Concentrated HCl.
conductivities below 10 µS/cm, except that a trace or flash of
7.7 Hydrochloric Acid (1+1)—Mix 1 volume of concen-
platinum black may be used on cells for measurements in the
trated HCl (sp gr 1.19) with 1 volume of water.
range of 0.1 to 10 µS/cm (see 9.4). Because of the cost and
7.8 Platinizing Solution—Dissolve 1.5 g of chloroplatinic
fragility of platinum cells, it is common practice to use
acid(H PtCl ·6H O)in50mLofwatercontaining0.0125gof
2 6 2
titanium, monel, and graphite electrodes for measurements
lead acetate (Pb(C H O ) ).
2 3 2 2
with accuracies on the order of 1%. Note that these electrodes
7.9 Potassium Chloride (KCl)—The assay of the potassium
may require special surface preparation. Titanium and monel
chloride must be 100.06 0.1%. This standardization grade of
electrodes are especially suitable for high resistance solutions
KClisavailablefromNISTandfromcommercialsources.Dry
such as ultrapure water, but may introduce a small surface
at 150°C for 2 h or until weight loss is less than 0.02%; store
resistance which limits their accuracy when the measured
in desiccator.
resistance is less than a few thousand ohms (1).
7.10 Potassium Chloride Reference Solution A—Dissolve
6.2.5 Itisrecommendedthatcellsintendedforthemeasure-
74.2460 g of KCl (weighed in air) in water and dilute to 1 Lat
mentofconductivitiesbelow10µS/cmbereservedexclusively
20 6 2°C in a Class A volumetric flask
...