ASTM D516-90(1995)e1

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e1
Designation: D 516 – 90 (Reapproved 1995)
Standard Test Method for
Sulfate Ion in Water
This standard is issued under the fixed designation D 516; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Editorial changes were made in June 1995.
1. Scope 3. Terminology
1.1 This turbidimetric test method covers the determination 3.1 Definitions—For definitions of terms used in this test
of sulfate in water in the range from 1 to 40 mg/L of sulfate ion method, refer to Terminology D 1129.
−−
(SO ).
4. Summary of Test Method
1.2 This test method was used successfully with drinking,
4.1 Sulfate ion is converted to a barium sulfate suspension
ground, and surface waters. It is the user’s responsibility to
ensure the validity of this test method for waters of untested under controlled conditions. A solution containing glycerin and
sodium chloride is added to stabilize the suspension and
matrices.
1.3 Former gravimetric and volumetric test methods have minimize interferences. The resulting turbidity is determined
by a nephelometer, spectrophotometer, or photoelectric colo-
been discontinued. Refer to Appendix X1 for historical infor-
mation. rimeter and compared to a curve prepared from standard sulfate
solutions.
1.4 This standard does not purport to address the safety
concerns, if any, associated with its use. It is the responsibility
5. Significance and Use
of the user of this standard to establish appropriate safety and
5.1 The determination of sulfate is important because it has
health practices and determine the applicability of regulatory
been reported that when this ion is present in excess of about
limitations prior to use.
250 mg/L in drinking water, it causes a cathartic action
2. Referenced Documents
(especially in children) in the presence of sodium and magne-
sium, and gives a bad taste to the water.
2.1 ASTM Standards:
D 1066 Practice for Sampling Steam
2 6. Interferences
D 1129 Terminology Relating to Water
6.1 Insoluble suspended matter in the sample must be
D 1192 Specification for Equipment for Sampling Water
removed. Dark colors that can not be compensated for in the
and Steam in Closed Conduits
procedure interfere with the measurement of suspended barium
D 1193 Specification for Reagent Water
sulfate (BaSO ).
D 2777 Practice for Determination of Precision and Bias of
6.2 Polyphosphates as low as 1 mg/L will inhibit barium
Applicable Methods of Committee D-19 on Water
sulfate precipitation causing a negative interference. Phospho-
D 3370 Practices for Sampling Water from Closed Con-
nates present in low concentrations, depending on the type of
duits
phosphonate, will also cause a negative interference. Silica in
E 60 Practice for Photometric and Spectrophotometric
excess of 500 mg/L may precipitate along with the barium
Methods for the Chemical Analysis of Metals
sulfate causing a positive interference. Chloride in excess of
E 275 Practice for Describing and Measuring Performance
5000 mg/L will cause a negative interference. Aluminum,
of Ultraviolet, Visible, and Near Infrared Spectrophotom-
polymers, and large quantities of organic material present in
eters
the test sample may cause the barium sulfate to precipitate
nonuniformly. In the presence of organic matter certain bacte-
This test method is under the jurisdiction of ASTM Committee D-19 on Water
ria may reduce sulfate to sulfide. To minimize the action of
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
sulfate reducing bacteria, samples should be refrigerated at 4°C
in Water.
when the presence of such bacteria is suspected.
Current edition approved June 29, 1990. Published December 1990. Originally
6.3 Although other ions normally found in water do not
published as D 516 – 38 T. Last previous edition D 516 – 88.
Annual Book of ASTM Standards, Vol 11.01.
appear to interfere, the formation of the barium sulfate suspen-
Annual Book of ASTM Standards, Vol 03.05.
sion is very critical. Determinations that are in doubt may be
Annual Book of ASTM Standards, Vol 03.06.
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D 516
checked by a gravimetric method in some cases, or by the by diluting with water 0.0, 2.0, 5.0, 10.0, 15.0, 20.0, 30.0, and
procedure suggested in Note 2. 40.0 mL of standard sulfate solution to 100-mL volumes in
volumetric flasks. These solutions will have sulfate ion con-
7. Apparatus
centrations of 0.0, 2.0, 5.0, 10.0, 15.0, 20.0, 30.0, and 40.0
7.1 Photometer—One of the following which are given in mg/L (ppm), respectively.
order of preference.
NOTE 1—A separate calibration curve must be prepared for each
7.1.1 Nephelometer or turbidimeter;
photometer and a new curve must be prepared if it is necessary to change
7.1.2 Spectrophotometer for use at 420 nm with light path of
the cell, lamp, or filter, or if any other alterations of instrument or reagents
4to5cm; are made. Check the curve with each series of tests by running two or
more solutions of known sulfate concentrations.
7.1.3 Filter photometer with a violet filter having a maxi-
mum near 420 nm and a light path of 4 to 5 cm.
11. Procedure
7.2 Stopwatch, if the magnetic stirrer is not equipped with
11.1 Filter the sample if it is turbid, and adjust the tempera-
an accurate timer.
ture to between 15 and 30°C.
7.3 Measuring Spoon, capacity 0.2 to 0.3 mL.
11.2 Pipet into a 250-mL beaker 100 mL or less of the clear
7.4 Filter photometers and photometric practices prescribed
sample containing between 0.5 and 4 mg of sulfate ion (Note
in this test method shall conform to Practice E 60; spectropho-
2). Dilute to 100 mL with water if required, and add 5.0 mL of
tometer practices shall conform to Practice E 275.
conditioning reagent (Note 1).
8. Reagents
NOTE 2—The solubility of BaSO is such that difficulty may be
8.1 Purity of Reagents—Reagent grade chemicals shall be
experienced in the determination of sulfate concentrations below about 5
mg/L (ppm). This can be overcome by concentrating the sample or by
used in all tests. Unless otherwise indicated, it is intended that
−−
adding 5 mL of standard sulfate solution (1 mL = 0.100 mg SO )tothe
all reagents shall conform to the specifications of the Commit- 4
5 sample before diluting to 100 mL. This will add 0.5 mg SO to the sample,
tee on Analytical Reagents of the American Chemical Society.
which must be subtracted from the final result.
Other grades may be used, provided it is first ascertained that
11.3 Mix in the stirring apparatus.
the reagent is of sufficiently high purity to permit its use
11.4 While the solution is being stirred, add a measured
without lessening the accuracy of the determination.
spoonful of BaCl crystals (0.3 g) and begin timing immedi-
8.2 Purity of Water—Unless otherwise indicated, references
ately.
to water shall be understood to mean reagent water conforming
11.5 Stir exactly 1.0 min at constant speed.
to Specification D 1193, Type III.
8.3 Barium Chloride—Crystals of barium chloride
NOTE 3—The stirring should be at a constant rate in all determinations.
(BaCl ·2H O) screened to 20 to 30 mesh. To prepare in the
2 2 The use of a magnetic stirrer has been found satisfactory for this purpose.
laboratory, spread crystals over a large watch glass, desiccate
11.6 Immediately after the stirring period has ended, pour
for 24 h, screen to remove any crystals that are not 20 to 30
solution into the cell
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