ASTM D516-22

• Abstract:

  SIGNIFICANCE AND USE; 5.1 The determination of sulfate is important because it has been reported that when this ion is present in excess of about 250 mg/L in drinking water, it causes a cathartic action (especially in children) in the presence of sodium and magnesium, and gives a bad taste to the water. ; 5.2 Test Method D4327 (“Test Method of Anions in Water by Suppressed Ion Chromatography”) may be used.; SCOPE; 1.1 This turbidimetric test method covers the determination of sulfate in water in the range from 5 mg/L to 40 mg/L of sulfate ion (SO4−−). ; 1.2 This test method was used successfully with drinking, ground, and surface waters. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices. ; 1.3 Former gravimetric and volumetric test methods have been discontinued. Refer to Appendix X1 for historical information. ; 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. ; 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. ; 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.05 - Inorganic Constituents in Water

• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D1066-18 - Standard Practice for Sampling Steam
• Effective Date: 01-Aug-2018
• Refers: ASTM D1066-18e1 - Standard Practice for Sampling Steam
• Effective Date: 01-Aug-2018
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D1066-11 - Standard Practice for Sampling Steam
• Effective Date: 15-Jun-2011
• Refers: ASTM D5810-96(2011) - Standard Guide for Spiking into Aqueous Samples
• Effective Date: 01-May-2011
• Refers: ASTM D4327-11 - Standard Test Method for Anions in Water by Suppressed Ion Chromatography
• Effective Date: 01-Mar-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM E275-08 - Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
• Effective Date: 15-Oct-2008
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007
• Refers: ASTM D1066-06 - Standard Practice for Sampling Steam
• Effective Date: 15-Dec-2006
• Refers: ASTM D1129-06ae1 - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006

Overview

ASTM D516-22: Standard Test Method for Sulfate Ion in Water provides a turbidimetric method for quantitative determination of sulfate ions (SO4²⁻) in water samples. The procedure is applicable for drinking water, ground water, and surface water, covering a measuring range from 5 mg/L to 40 mg/L of sulfate. Sulfate analysis is important for water quality assessment, as excessive sulfate (above 250 mg/L) in drinking water can impart an undesirable taste and have laxative effects, particularly in the presence of sodium and magnesium.

This international ASTM standard aligns with globally recognized principles, making it reliable for regulatory and industrial compliance. It replaces earlier gravimetric and volumetric methods, streamlining sulfate testing with improved performance and procedural clarity.

Key Topics

• Scope and Applicability:
  • Measures sulfate ion concentrations from 5 mg/L to 40 mg/L.
  • Suitable for drinking water, ground water, and surface water matrices.
  • Users are responsible for validating applicability to untested waters.
• Test Method Summary:
  • Sulfate ions are precipitated as barium sulfate under controlled conditions.
  • The resulting turbidity is measured using a suitable photometric instrument (nephelometer, spectrophotometer, or photoelectric colorimeter).
  • Turbidity values are compared against a calibration curve prepared from sulfate standards.
• Quality Assurance:
  • Requires use of standard solutions, blanks, calibration verification, and quality control samples.
  • Calibration correlations must reach or exceed a coefficient of 0.990.
• Interferences:
  • Polyphosphates, phosphonates, high silica, and chloride levels can interfere with results.
  • Ensuring proper sample preparation and recognizing matrix interference is critical for accuracy.
• Precision and Bias:
  • Extensive precision and bias data from interlaboratory studies are provided within the standard.
  • Recovery and accuracy requirements are defined for robust quality control.

Applications

• Drinking Water Quality Monitoring:
  • Ensures compliance with health guidelines and taste standards by determining sulfate concentrations efficiently.
• Ground and Surface Water Testing:
  • Monitors environmental water sources for natural or anthropogenic sulfate contamination.
• Regulatory Compliance:
  • Widely used by laboratories and municipalities to satisfy local, national, and international drinking water standards.
• Industrial Water Analysis:
  • Assesses process water and wastewater to control scaling, corrosion, and discharge quality.
• Support for Environmental Assessments:
  • Provides baseline and impact data for sulfate levels in the environment.

Related Standards

• ASTM D4327: Test Method for Anions in Water by Suppressed Ion Chromatography - an alternative test method for sulfate.
• ASTM D1066: Practice for Sampling Steam - relevant for collecting water samples.
• ASTM D1129: Terminology Relating to Water.
• ASTM D1193: Specification for Reagent Water - defines water purity requirements.
• ASTM D3370: Practices for Sampling Water from Flowing Process Streams.
• ASTM D2777: Practice for Determination of Precision and Bias - important for method validation.
• ASTM D5810 & D5847: Guides for spiking samples and quality control specifications.
• ASTM E60 & E275: Practices for spectrophotometric analysis and instrument performance.

Practical Value

The ASTM D516-22 test method allows laboratories, utilities, and industrial operators to easily and reliably quantify sulfate in water, ensuring water quality, public health, and regulatory compliance. Its robust turbidimetric procedure, supported by detailed quality control protocols, enables repeatable and defensible results for a wide range of water testing scenarios, making it a foundational tool in environmental and analytical chemistry.

Keywords: sulfate analysis, ASTM D516-22, drinking water testing, water quality standard, sulfate ion, turbidimetric method, ground water, surface water, sulfate in water, water laboratory analysis.

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D516 − 22
Standard Test Method for
Sulfate Ion in Water
This standard is issued under the fixed designation D516; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
1.1 This turbidimetric test method covers the determination
D3370 Practices for Sampling Water from Flowing Process
of sulfate in water in the range from 5 mg ⁄L to 40 mg/L of
−− Streams
sulfate ion (SO ).
D4327 Test Method for Anions in Water by Suppressed Ion
1.2 This test method was used successfully with drinking,
Chromatography
ground, and surface waters. It is the user’s responsibility to
D5810 Guide for Spiking into Aqueous Samples
ensure the validity of this test method for waters of untested
D5847 Practice for Writing Quality Control Specifications
matrices.
for Standard Test Methods for Water Analysis
E60 Practice for Analysis of Metals, Ores, and Related
1.3 Former gravimetric and volumetric test methods have
been discontinued. Refer to Appendix X1 for historical infor- Materials by Spectrophotometry
E275 Practice for Describing and Measuring Performance of
mation.
Ultraviolet and Visible Spectrophotometers
1.4 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3. Terminology
standard.
3.1 Definitions:
1.5 This standard does not purport to address all of the
3.1.1 For definitions of terms used in this standard, refer to
safety concerns, if any, associated with its use. It is the
Terminology D1129.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 Sulfate ion is converted to a barium sulfate suspension
1.6 This international standard was developed in accor-
under controlled conditions. A solution containing glycerin and
dance with internationally recognized principles on standard-
sodium chloride is added to stabilize the suspension and
ization established in the Decision on Principles for the
minimize interferences. The resulting turbidity is determined
Development of International Standards, Guides and Recom-
by a nephelometer, spectrophotometer, or photoelectric colo-
mendations issued by the World Trade Organization Technical
rimeter and compared to a curve prepared from standard sulfate
Barriers to Trade (TBT) Committee.
solutions.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 The determination of sulfate is important because it has
D1066 Practice for Sampling Steam
been reported that when this ion is present in excess of about
D1129 Terminology Relating to Water
250 mg/L in drinking water, it causes a cathartic action
D1193 Specification for Reagent Water
(especially in children) in the presence of sodium and
magnesium, and gives a bad taste to the water.
5.2 Test Method D4327 (“Test Method of Anions in Water
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
by Suppressed Ion Chromatography”) may be used.
in Water.
Current edition approved Dec. 1, 2022. Published March 2023. Originally
6. Interferences
approved in 1938. Last previous edition approved in 2016 as D516 – 16. DOI:
10.1520/D0516-22.
6.1 Insoluble suspended matter in the sample must be
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
removed. Dark colors that cannot be compensated for in the
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
procedure interfere with the measurement of suspended barium
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. sulfate (BaSO ).
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D516 − 22
6.2 Polyphosphates as low as 1 mg/L will inhibit barium tee on Analytical Reagents of the American Chemical Society.
sulfate precipitation causing a negative interference. Phospho- Other grades may be used, provided it is first ascertained that
nates present in low concentrations, depending on the type of the reagent is of sufficiently high purity to permit its use
phosphonate, will also cause a negative interference. without lessening the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, reference
6.3 Silica in excess of 500 mg/L may precipitate along with
to water shall be understood to mean reagent water conforming
the barium sulfate causing a positive interference.
to Specification D1193, Type I. Other reagent water types may
6.4 Chloride in excess of 5000 mg/L will cause a negative
be used provided it is first ascertained that the water is of
interference.
sufficiently high purity to permit its use without adversely
affecting the precision and bias of the test method. Type II
6.5 Aluminum, polymers, and large quantities of organic
water was specified at the time of round robin testing of this
material present in the test sample may cause the barium
test method.
sulfate to precipitate nonuniformly.
8.3 Barium Chloride—Crystals of barium chloride
6.6 In the presence of organic matter certain bacteria may
(BaCl ·2H O) screened to 20 to 30 mesh. To prepare in the
2 2
reduce sulfate to sulfide. To minimize the action of sulfate
laboratory, spread crystals over a large watch glass, desiccate
reducing bacteria, samples should be refrigerated at 4 °C when
for 24 h, screen to remove any crystals that are not 20 to 30
the presence of such bacteria is suspected.
mesh, and store in a clean, dry jar.
6.7 Although other ions normally found in water do not
8.4 Conditioning Reagent—Place 30 mL of concentrated
appear to interfere, the formation of the barium sulfate suspen-
hydrochloric acid (HCl, sp gr 1.19), 300 mL reagent water,
sion is very critical. Determinations that are in doubt may be
100 mL 95 % ethanol or isopropanol and 75 g sodium chloride
checked by a gravimetric method in some cases, or by the
(NaCl) in a container. Add 50 mL glycerol and mix.
procedure suggested in 11.2.1.
−−
8.5 Sulfate Solution, Standard (1 mL = 0.100 mg SO )—
Dissolve 0.1479 g of anhydrous sodium sulfate (Na SO ) in
2 4
7. Apparatus
water, and dilute with water to 1 L in a volumetric flask. A
7.1 Photometer—One of the following which are given in
purchased stock solution of adequate purity is also acceptable.
order of preference.
8.6 Filter Paper—Purchase suitable filter paper. Typically
7.1.1 Nephelometer or turbidimeter;
the filter papers have a pore size of 0.45 μm membrane.
7.1.2 Spectrophotometer for use at 420 nm with light path of Material such as fine-textured, acid-washed, ashless paper, or
4 cm to 5 cm;
glass fiber paper are acceptable. The user must first ascertain
that the filter paper is of sufficient purity to use without
7.1.3 Filter photometer with a violet filter having a maxi-
adversely affecting the bias and precision of the test method.
mum near 420 nm and a light path of 4 cm to 5 cm.
7.2 Stopwatch, if the magnetic stirrer is not equipped with
9. Sampling
an accurate timer.
9.1 Collect the sample in accordance with Practice D1066,
and Practices D3370, as applicable.
7.3 Measuring Spoon, capacity 0.2 mL to 0.3 mL.
7.4 Filter photometers and photometric practices prescribed
10. Calibration
in this test method shall conform to Practice E60; spectropho-
10.1 Follow the procedure given in Section 11, using
tometer practices shall conform to Practice E275.
appropriate amounts of the standard sulfate solution prepared
in accordance with 8.5 and prepare a calibration curve showing
7.5 Laboratory Glassware—All glassware should be in
sulfate ion content in milligrams per litre plotted against the
good condition, clean, and free of contaminating substances.
corresponding photometer readings (10.2).
7.5.1 If the testing is for regulatory purposes, volumetric
flasks should be of Type A precision and serialized for quality
10.2 Prepare standards by diluting with water 0.0 mL,
control tracking.
5.0 mL, 10.0 mL, 15.0 mL, 20.0 mL, 30.0 mL, and 40.0 mL of
standard sulfate solution to 100 mL volumes in volumetric
7.6 Stirring Apparatus—A magnetic stirrer should be used
flasks. These solutions will have sulfate ion concentrations of
along with a magnetic stir bar appropriately sized for the
0.0 mg ⁄L, 5.0 mg ⁄L, 10.0 mg ⁄L, 15.0 mg ⁄L, 20.0 mg ⁄L,
labware in use.
30.0 mg ⁄L, and 40.0 mg/L (ppm), respectively.
7.7 Weighing Apparatus—A scale or analytical balance of
10.2.1 A separate calibration curve must be prepared for
the appropriate accuracy and precision should be used. It each photometer and a new curve must be prepared if it is
should be calibrated and within its calibration interval.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
8. Reagents and Materials
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents not listed by the American Chemical
8.1 Purity of Reagents—Reagent grade chemicals shall be
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
used in all tests. Unless otherwise indicated, it is intended that
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
all reagents shall conform to the specifications of the Commit- copeial Convention, Inc. (USPC), Rockville, MD.
D516 − 22
necessary to change the cell, lamp, or filter, or if any other 13.2 The overall and single-operator precision of the test
alterations of instrument or reagents are made. Check the curve method, within its designated range, varies with the quantity
with each series of tests by running two or more solutions of being tested according to Table 1 for reagent water and Table
known sulfate concentrations. 2 for drinking, ground, and surface waters.
13.2.1 Seven laboratories participated in the round robin at
11. Procedure
three levels in triplicate, making a total of 21 observations at
each level for reagent water and for matrix water (drinking,
11.1 Filter (8.6) the sample if it is turbid through a 0.45 μm
membrane and adjust the temperature to between 15 °C and ground, and surface water).
30 °C.
13.3 Recoveries of known amounts of sulfate from reagent
11.2 Pipette into a 250 mL beaker 100 mL or less of the water and drinking, ground, and surface waters are as shown in
Table 3.
clear sample containing between 0.5 mg and 4 mg of sulfate
ion (11.2.1). Dilute to 100 mL with water if required, and add 13.3.1 A table for estimating the bias of the test method
through its applicable concentration range can be found in
5.0 mL of conditioning reagent (10.2.1).
11.2.1 The solubility of BaSO is such that difficulty may be Table 4.
13.3.2 These collaborative test data were obtained on re-
experienced in the determination of sulfate concentrations
agent grade water and natural waters. For other matrices, these
below about 5 mg/L (ppm). This can be overcome by concen-
data may not apply.
trating the sample or by adding 5 mL of standard sulfate
−−
solution (1 mL = 0.100 mg SO ) to the sample before
13.4 Precision and bias for this test method conforms to
diluting to 100 mL. This will add 0.5 mg SO to the sample,
Practice D2777 – 86, which was in place at the time of
which must be subtracted from the final result.
collaborative testing. Under the allowances made in 1.4 of
D2777 – 13, these precision and bias data do meet existing
11.3 Mix in the stirring apparatus.
requirements for interlaboratory studies of Committee D19 test
11.4 While the solution is being stirred, add a measured
methods.
spoonful of BaCl crystals (0.3 g) and begin timing immedi-
ately.
14. Quality Control (QC)
11.5 Stir exactly 1.0 min at constant speed.
14.1 The following quality control information is recom-
mended for the determination of sulfate ion in water.
NOTE 1—The stirring should be at a constant rate in all determinations.
The use of a magnetic stirrer has been found satisfactory for this purpose.
14.2 Calibration and Calibration Verification:
11.6 Immediately after the stirring period has ended, pour
14.2.1 Analyze at least three working standards containin
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D516 − 16 D516 − 22
Standard Test Method for
Sulfate Ion in Water
This standard is issued under the fixed designation D516; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This turbidimetric test method covers the determination of sulfate in water in the range from 55 mg ⁄L to 40 mg/L of sulfate
−−
ion (SO ).
1.2 This test method was used successfully with drinking, ground, and surface waters. It is the user’s responsibility to ensure the
validity of this test method for waters of untested matrices.
1.3 Former gravimetric and volumetric test methods have been discontinued. Refer to Appendix X1 for historical information.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Flowing Process Streams
D4327 Test Method for Anions in Water by Suppressed Ion Chromatography
D5810 Guide for Spiking into Aqueous Samples
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
E60 Practice for Analysis of Metals, Ores, and Related Materials by Spectrophotometry
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.
Current edition approved June 1, 2016Dec. 1, 2022. Published June 2016March 2023. Originally approved in 1938. Last previous edition approved in 20112016 as
D516 – 11.D516 – 16. DOI: 10.1520/D0516-16.10.1520/D0516-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D516 − 22
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.
4. Summary of Test Method
4.1 Sulfate ion is converted to a barium sulfate suspension under controlled conditions. A solution containing glycerin and sodium
chloride is added to stabilize the suspension and minimize interferences. The resulting turbidity is determined by a nephelometer,
spectrophotometer, or photoelectric colorimeter and compared to a curve prepared from standard sulfate solutions.
5. Significance and Use
5.1 The determination of sulfate is important because it has been reported that when this ion is present in excess of about 250 mg/L
in drinking water, it causes a cathartic action (especially in children) in the presence of sodium and magnesium, and gives a bad
taste to the water.
5.2 Test Method D4327 (“Test Method of Anions in Water by Suppressed Ion Chromatography”) may be used.
6. Interferences
6.1 Insoluble suspended matter in the sample must be removed. Dark colors that cannot be compensated for in the procedure
interfere with the measurement of suspended barium sulfate (BaSO ).
6.2 Polyphosphates as low as 1 mg/L will inhibit barium sulfate precipitation causing a negative interference. Phosphonates
present in low concentrations, depending on the type of phosphonate, will also cause a negative interference.
6.3 Silica in excess of 500 mg/L may precipitate along with the barium sulfate causing a positive interference.
6.4 Chloride in excess of 5000 mg/L will cause a negative interference.
6.5 Aluminum, polymers, and large quantities of organic material present in the test sample may cause the barium sulfate to
precipitate nonuniformly.
6.6 Polyphosphates as low as 1 mg/L will inhibit barium sulfate precipitation causing a negative interference. Phosphonates
present in low concentrations, depending on the type of phosphonate, will also cause a negative interference. Silica in excess of
500 mg/L may precipitate along with the barium sulfate causing a positive interference. Chloride in excess of 5000 mg/L will cause
a negative interference. Aluminum, polymers, and large quantities of organic material present in the test sample may cause the
barium sulfate to precipitate nonuniformly. In the presence of organic matter certain bacteria may reduce sulfate to sulfide. To
minimize the action of sulfate reducing bacteria, samples should be refrigerated at 4°C4 °C when the presence of such bacteria is
suspected.
6.7 Although other ions normally found in water do not appear to interfere, the formation of the barium sulfate suspension is very
critical. Determinations that are in doubt may be checked by a gravimetric method in some cases, or by the procedure suggested
in Note 211.2.1.
7. Apparatus
7.1 Photometer—One of the following which are given in order of preference.
7.1.1 Nephelometer or turbidimeter;
7.1.2 Spectrophotometer for use at 420 nm with light path of 44 cm to 5 cm;
7.1.3 Filter photometer with a violet filter having a maximum near 420 nm and a light path of 44 cm to 5 cm.
D516 − 22
7.2 Stopwatch, if the magnetic stirrer is not equipped with an accurate timer.
7.3 Measuring Spoon, capacity 0.20.2 mL to 0.3 mL.
7.4 Filter photometers and photometric practices prescribed in this test method shall conform to Practice E60; spectrophotometer
practices shall conform to Practice E275.
7.5 Laboratory Glassware—All glassware should be in good condition, clean, and free of contaminating substances.
7.5.1 If the testing is for regulatory purposes, volumetric flasks should be of Type A precision and serialized for quality control
tracking.
7.6 Stirring Apparatus—A magnetic stirrer should be used along with a magnetic stir bar appropriately sized for the labware in
use.
7.7 Weighing Apparatus—A scale or analytical balance of the appropriate accuracy and precision should be used. It should be
calibrated and within its calibration interval.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society. Other
grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening
the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean reagent water conforming to
Specification D1193, Type I. Other reagent water types may be used provided it is first ascertained that the water is of sufficiently
high purity to permit its use without adversely affecting the precision and bias of the test method. Type II water was specified at
the time of round robin testing of this test method.
8.3 Barium Chloride—Crystals of barium chloride (BaCl ·2H O) screened to 20 to 30 mesh. To prepare in the laboratory, spread
2 2
crystals over a large watch glass, desiccate for 24 h, screen to remove any crystals that are not 20 to 30 mesh, and store in a clean,
dry jar.
8.4 Conditioning Reagent—Place 30 mL of concentrated hydrochloric acid (HCl, sp gr 1.19), 300 mL reagent water, 100 mL
100 mL 95 % ethanol or isopropanol and 75 g sodium chloride (NaCl) in a container. Add 50 mL glycerol and mix.
−−
8.5 Sulfate Solution, Standard (1 mL = 0.100 mg SO )——DissolveDissolve 0.1479 g of anhydrous sodium sulfate (Na SO )
4 2 4
in water, and dilute with water to 1 L in a volumetric flask. A purchased stock solution of adequate purity is also acceptable.
8.6 Filter Paper—Purchase suitable filter paper. Typically the filter papers have a pore size of 0.45-μm0.45 μm membrane.
Material such as fine-textured, acid-washed, ashless paper, or glass fiber paper are acceptable. The user must first ascertain that
the filter paper is of sufficient purity to use without adversely affecting the bias and precision of the test method.
9. Sampling
9.1 Collect the sample in accordance with Practice D1066, and Practices D3370, as applicable.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For Suggestionssuggestions on the testing of reagents not listed by the American Chemical Society, see
AnnualAnalar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial
Convention, Inc. (USPC), Rockville, MD.
D516 − 22
10. Calibration
10.1 Follow the procedure given in Section 11, using appropriate amounts of the standard sulfate solution prepared in accordance
with 8.5 and prepare a calibration curve showing sulfate ion content in milligrams per litre plotted against the corresponding
photometer readings (10.2).
10.2 Follow the procedure given in Section 11, using appropriate amounts of the standard sulfate solution prepared in accordance
with 8.5 and prepare a calibration curve showing sulfate ion content in milligrams per litre plotted against the corresponding
photometer readings (Note 1). Prepare standards by diluting with water 0.0, 5.0, 10.0, 15.0, 20.0, 30.0,0.0 mL, 5.0 mL, 10.0 mL,
15.0 mL, 20.0 mL, 30.0 mL, and 40.0 mL of standard sulfate solution to 100-mL100 mL volumes in volumetric flasks. These
solutions will have sulfate ion concentrations of 0.0,0.0 mg 5.0,⁄L, 5.0 mg 10.0,⁄L, 10.0 mg 15.0,⁄L, 15.0 mg 20.0,⁄L, 20.0 mg
30.0,⁄L, 30.0 mg ⁄L, and 40.0 mg/L (ppm), respectively.
NOTE 1—A separate calibration curve must be prepared for each photometer and a new curve must be prepared if it is necessary to change the cell, lamp,
or filter, or if any other alterations of instrument or reagents are made. Check the curve with each series of tests by running two or more solutions of known
sulfate concentrations.
10.2.1 A separate calibration curve must be prepared for each photometer and a new curve must be prepared if it is necessary to
change the cell, lamp, or filter, or if any other alterations of instrument or reagents are made. Check the curve with each series of
tests by running two or more solutions of known sulfate concentrations.
11. Procedure
11.1 Filter (8.6) the sample if it is turbid through a 0.45-μm0.45 μm membrane and adjust the temperature to between 15 and
30°C.15 °C and 30 °C.
11.2 Pipette into a 250-mL250 mL beaker 100 mL or less of the clear sample containing between 0.50.5 mg and 4 mg of sulfate
ion (Note 211.2.1). Dilute to 100 mL with water if required, and add 5.0 mL of conditioning reagent (Note 110.2.1).
NOTE 2—The solubility of BaSO is such that difficulty may be experienced in the determination of sulfate concentrations below about 5 mg/L (ppm).
−−
This can be overcome by concentrating the sample or by adding 5 mL of standard sulfate solution (1 mL = 0.100 mg SO ) to the sample before diluting
to 100 mL. This will add 0.5 mg SO to the sample, which must be subtracted from the final result.
11.2.1 The solubility of BaSO is such that difficulty may be experienced in the determination of sulfate concentrations below
about 5 mg/L (ppm). This can be overcome by concentrating the sample or by adding 5 mL of standard sulfate solution (1
−−
mL = 0.100 mg SO ) to the sample before diluting to 100 mL. This will add 0.5 mg SO to the sample, which must be subtracted
4 4
from the final result.
11.3 Mix in the stirring apparatus.
11.4 While the solution is being stirred, add a measured spoonful of BaCl crystals (0.3 g) and begin timing immediately.
11.5 Stir exactly 1.0 min at constant speed.
NOTE 1—The stirring should be at a constant rate in all determinations. The use of a magnetic stirrer has been found satisfactory for this purpose.
11.6 Immediately after the stirring period has ended, pour solution into the cell and measure the turbidity at 30-s intervals for 4
min. Record the maximum reading obtained in the 4-min period.
11.7 If the sample contains color or turbidity, run a sample blank using the procedure 11.2 through 11.6 without the addition of
the barium chloride.
11.8 If interferences are suspected, dilute the sample with an equal volume of water, and determine the sulfate concentration again.
If the value so determined is one half that in the undiluted sample, interferences may be assumed to be absent.
D516 − 22
NOTE 4—After dilution, if interfere
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