ASTM D1179-99
(Test Method)Standard Test Methods for Fluoride Ion in Water
Standard Test Methods for Fluoride Ion in Water
SCOPE
1.1 These test methods cover the determination of fluoride ion in water. The following two test methods are given: Sections Test Method A (Distillation) 7 to 14 Test Method B (Ion Selective Electrode) 15 to 22
1.2 Test Method A covers the accurate measurement of total fluoride in water through isolation of the fluoride by distillation and subsequent measurement in the distillate by use of the ion selective electrode method. The procedure covers the range from 0.1 to 2.6 mg/L of fluoride.
1.3 Test Method B covers the accurate measurement of simple fluoride ion in water by means of an ion selective electrode. With this test method, distillation is eliminated because the electrode is not affected by the interferences common to colorimetric procedures. Concentrations of fluoride from 0.1 to 1000 mg/L may be measured.
1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For a specific precautionary statement, see 12.1.2.
1.5 Former Test Method A, SPADNS Photometric Procedure, was discontinued. Refer to Appendix X1 for historical information.
General Information
Relations
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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 1179 – 99
Standard Test Methods for
Fluoride Ion in Water
This standard is issued under the fixed designation D 1179; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope D 2777 Practice for Determination of Precision and Bias of
2 Applicable Methods of Committee D-19 on Water
1.1 These test methods cover the determination of fluoride
D 3370 Practices for Sampling Water from Closed Con-
ion in water. The following two test methods are given:
duits
Sections
Test Method A—Distillation 7 to 13
3. Terminology
Test Method B—Ion Selective Electrode 14 to 22
3.1 Definitions—For definitions of terms used in these test
1.2 Test Method A covers the accurate measurement of total
methods, refer to Terminology D 1129.
fluoride in water through isolation of the fluoride by distillation
and subsequent measurement in the distillate by use of the ion
4. Significance and Use
selective electrode (ISE) method. The procedure covers the
4.1 Simple and complex fluoride ions are found in natural
range from 0.1 to 2.6 mg/L of fluoride.
waters. Fluoride forms complexing ions with silicon, alumi-
1.3 Test Method B covers the accurate measurement of
num, and boron. These complexes may originate from the use
simple fluoride ion in water by means of an ion selective
of fluorine compounds by industry.
electrode. With this test method, distillation is eliminated
4.2 Fluoridation of drinking water to prevent dental caries is
because the electrode is not affected by the interferences
practiced by a large number of communities in this country.
common to colorimetric procedures. Concentrations of fluoride
Fluoride is monitored to assure that an optimum treatment level
from 0.1 to 1000 mg/L may be measured.
of 1.4 to 2.4 mg/L, depending on the corresponding range of
1.4 This standard does not purport to address all of the
ambient temperatures of 32 to 10°C, is maintained.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Purity of Reagents
priate safety and health practices and determine the applica-
5.1 Reagent grade chemicals shall be used in all tests.
bility of regulatory limitations prior to use. For a specific
Unless otherwise indicated, it is intended that all reagents shall
precautionary statement, see 12.1.2.
conform to the specifications of the Committee on Analytical
1.5 Former Test Method A, SPADNS Photometric Proce-
Reagents of the American Chemical Society, where such
dure, was discontinued. Refer to Appendix X1 for historical
specifications are available. Other grades may be used, pro-
information.
vided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of
2. Referenced Documents
the determination.
2.1 ASTM Standards:
3 5.2 Purity of Water—Unless otherwise indicated, references
D 1066 Practice for Sampling Steam
to water shall be understood to mean Type I reagent water
D 1129 Terminology Relating to Water
conforming to Specification D 1193.
D 1192 Specification for Equipment for Sampling Water
and Steam in Closed Conduits
6. Sampling
D 1193 Specification for Reagent Water
6.1 Collect the sample in accordance with Practice D 1066,
Specification D 1192, or Practices D 3370, as applicable.
These test methods are under the jurisdiction of ASTM Committee D-19 on
Water and are the direct responsibility of Subcommittee D19.05 on Inorganic
Constituents in Water. Reagent Chemicals, American Chemical Society Specifications, American
Current edition approved Feb. 10, 1999. Published April 1999. Originally Chemical Society, Washington, DC. For suggestions on the testing of reagents not
published as D 1179 – 51. Last previous edition D 1179 – 93. listed by the American Chemical Society, see Analar Standards for Laboratory
Bellack, E., “Simplified Fluoride Distillation Method,’’ Journal of the Ameri- Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
can Water Works Association, Vol 50, 1958, p. 530. and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
Annual Book of ASTM Standards, Vol 11.01. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 1179–99
TEST METHOD A—DISTILLATION
7. Scope
7.1 This test method is applicable to the accurate determi-
nation of fluoride ion in water, including most wastewaters.
This test method may not be applicable to concentrated brines
and oily wastes.
7.2 This test method was tested on reagent water and
wastewater. It is the user’s responsibility to ensure the validity
of this test method for waters of untested matrices.
8. Summary of Test Method
8.1 The fluoride is distilled as hydrofluosilicic acid and is
determined by the ion selective electrode.
9. Interferences
9.1 In sample distillation, interferences may be experienced
due to the following factors.
9.1.1 Aluminum in excess of 300 mg/L and silicon dioxide
as colloidal silica in excess of 400 mg/L will hold up in the
A—Heating mantle (quartz).
condenser to a certain extent, causing low results and acting as
B—Round-bottom flask, 1000 mL.
a positive interference for subsequent samples of lower fluoride
C—Adapter with thermometer opening.
content. In these cases, the condenser should be flushed with D—Thermometer, 200°C.
E—Connecting tube.
300 to 400 mL of water and the washwater added to the
F—Graham condenser, 300 mm.
distillate. The distillate may then be diluted to 1.0 L. If the
G—Vessel, calibrated at 300 mL.
analyst prefers, a smaller sample aliquot diluted to 300 mL may
FIG. 1 Distillation Assembly for Fluoride Isolation
be selected for distillation.
9.1.2 Sea water, brines, and generally samples of dissolved
solids in excess of 2500 mg/L will cause bumping in the
12.1.1 Place 400 mL of water in the distilling flask and add
distillation flask. Dilution of the sample with fluoride-free
200 mL of concentrated H SO (sp gr 1.84). Observe the usual
2 4
water to a lesser-dissolved solids concentration is an effective
precautions while mixing the H SO by slow addition of the
2 4
remedy to bumping.
acid accompanied by constant swirling. Add sufficient boiling
9.1.3 Samples containing oily matter which may result in a
stones and assemble the apparatus as shown in Fig. 1. Heat the
two-phase distillate, an emulsion, or anything other than a clear
solution in the flask, preferably with an electric heating mantle,
distillate may prevent accurate measurement of fluoride. Such
until the temperature of the contents reaches exactly 180°C. (A
samples should be extracted initially with a suitable solvent
quartz heating mantle is preferred in order to reach the required
(such as ether, chloroform, benzene, and similar solvents) to
180°C in a minimum time.) While heating, the tip of the
remove the oily material, and then warmed on a steam bath to
thermometer must extend below the level of the liquid in the
remove traces of the added solvent.
flask. Discard the distillate. The procedure, to this step, serves
to adjust the acid-water ratio for subsequent distillations.
10. Apparatus
12.1.2 Caution—Cool the acid-water mixture to below
10.1 Distillation Assembly—Glassware consisting of a 1-L,
100°C, slowly add 300 mL of sample, and mix thoroughly
round bottom, borosilicate boiling flask, an adapter with a
before heating. Distill as described in 12.1.1, until the tempera-
thermometer opening, a connecting tube, a condenser, and a
ture reaches 180°C. Do not allow the temperature to exceed
thermometer reading to 200°C, assembled as shown in Fig. 1.
180°C; excessive carryover of sulfate occurs at temperatures of
Standard-taper or spherical ground glass joints shall be used
or above 180°C, resulting with interference in the subsequent
throughout the apparatus.
fluoride measurement.
12.1.3 Collect the distillate in any suitably calibrated vessel.
11. Reagents
If a calibrated vessel is used, it is possible to dispense with
11.1 Silver Sulfate (Ag SO ), powder.
2 4
thermometer readings and stop the distillation when the vol-
11.2 Sodium Arsenite Solution (2 g/L)—Dissolve2gof
ume of distillate reaches 300 mL.
sodium arsenite (NaAsO ) in water and dilute to 1 L.
12.1.4 In the case of samples containing chlorides in con-
11.3 Sodium Fluoride Solution, Standard (1.0 mL = 0.01
centrations which may interfere in the subsequent reaction, add
mg F)—Dissolve 0.2210 g of sodium fluoride (NaF) in water
Ag SO to the distillation mixture at a rate of 5 mg/mg of
2 4
and dilute to 1.0 L. Dilute 100 mL of this solution to 1.0 L with
chloride.
water. Store in borosilicate glass or polyethylene.
11.4 Sulfuric Acid (H SO ), Concentrated (sp gr 1:84).
2 4
12. Procedure
Glass beads must be of a soft glass (rather than borosilicate). Use about 12
12.1 Distillation: beads. Soft beads will provide silica to the fluoride and protect the distillation flask.
D 1179–99
TABLE 1 Determination of Precision—Final Statistics for Test TABLE 3 Allowable Interference Levels with Selective Ion
A
Method A Electrode and Buffer
Maximum Allowable Concentration at
NOTE 1—Precision of Test Method A was determined from round robin
Interfering Ion
−
1.0 mg/L F
data using distillation with ion selective electrode finish.
+3
Al 0.5
Amount added, mg/L 0.150 0.560 0.840 2.600
+4
Si 50
+3
Reagent Water Fe 65
A
Concentration, x 0.147 0.558 0.818 2.520
A
Refer to 16.2 for description of interfering cations.
A
S 0.033 0.053 0.034 0.099
t
A
S 0.013 0.017 0.004 0.031
o
Wastewater
A A
Concentration, x 0.126 0.505 0.771 2.454 15. Summary of Test Method
A
S 0.048 0.068 0.092 0.070
t
A 15.1 The fluoride is determined potentiometrically using an
S 0.018 0.013 0.017 0.030
o
ion selective fluoride electrode in conjunction with a standard
A
Calculated with outlier point removed from data base.
single junction, sleeve-type reference electrode, and a pH
meter having an expanded millivolt scale, or an ISE meter
having a direct concentration scale for fluoride.
12.1.5 The acid-water distilling solution may be used re-
15.2 The fluoride electrode consists of a lanthanum fluoride
peatedly until the buildup of interference materials equals the
crystal across which a potential is developed by fluoride
concentration given in Section 9.
,
6 7
ions. The cell may be represented by Ag/AgCl, Cl (0.3), F
12.2 Analysis:
(0.001) LaF /test solution/KCl/AgCl/Ag.
12.2.1 Use Test Method B (Ion Selective Electrode) with the
buffer solution described in 18.1.
16. Interferences
16.1 Extremes of pH i
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.