ASTM D511-14(2021)e1
(Test Method)Standard Test Methods for Calcium and Magnesium In Water
Standard Test Methods for Calcium and Magnesium In Water
SIGNIFICANCE AND USE
4.1 Calcium and magnesium salts in water are the primary components of water hardness which can cause pipe or tube scaling.
SCOPE
1.1 These test methods cover the determination of calcium and magnesium in water by complexometric titration and atomic absorption spectrometric procedures. Two test methods are included, as follows:
Sections
Test Method A—Complexometric Titration
7 – 15
Test Method B—Atomic Absorption Spectrometric
16 – 25
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversion to inch-pound units that are provided for information only and are not considered standard.
1.3 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. Specific hazard statements are given in 12.2.6 and 20.6.
1.4 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.
General Information
Relations
Standards Content (Sample)
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.
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Designation: D511 − 14 (Reapproved 2021)
Standard Test Methods for
Calcium and Magnesium In Water
This standard is issued under the fixed designation D511; 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.
ε NOTE—The WTO caveat was added editorially in December 2021.
1. Scope D3370 Practices for Sampling Water from Flowing Process
Streams
1.1 These test methods cover the determination of calcium
D4691 Practice for Measuring Elements in Water by Flame
and magnesium in water by complexometric titration and
Atomic Absorption Spectrophotometry
atomic absorption spectrometric procedures. Two test methods
D4841 Practice for Estimation of Holding Time for Water
are included, as follows:
Samples Containing Organic and Inorganic Constituents
Sections
D5810 Guide for Spiking into Aqueous Samples
Test Method A—Complexometric Titration 7–15
Test Method B—Atomic Absorption Spectrometric 16–25 D5847 Practice for Writing Quality Control Specifications
for Standard Test Methods for Water Analysis
1.2 The values stated in SI units are to be regarded as
standard. The values given in parentheses are mathematical
3. Terminology
conversion to inch-pound units that are provided for informa-
3.1 Definitions—For definitions of terms used in these test
tion only and are not considered standard.
methods, refer to Terminology D1129.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 Calcium and magnesium salts in water are the primary
priate safety, health, and environmental practices and deter-
components of water hardness which can cause pipe or tube
mine the applicability of regulatory limitations prior to use.
scaling.
Specific hazard statements are given in 12.2.6 and 20.6.
1.4 This international standard was developed in accor-
5. Purity of Reagents
dance with internationally recognized principles on standard-
5.1 Reagent grade chemicals shall be used in all tests.
ization established in the Decision on Principles for the
Unless otherwise indicated, it is intended that all reagents shall
Development of International Standards, Guides and Recom-
conform to the specifications of the Committee on Analytical
mendations issued by the World Trade Organization Technical
Reagents of the American Chemical Society. Other grades
Barriers to Trade (TBT) Committee.
may be used, provided it is first ascertained that the reagent is
of sufficiently high purity to permit its use without lessening
2. Referenced Documents
the accuracy of the determination.
2.1 ASTM Standards:
5.2 Purity of Water—Unless otherwise indicated, references
D1129 Terminology Relating to Water
towatershallbeunderstoodtomeanreagentwaterconforming
D1193 Specification for Reagent Water
to Specification D1193, Type 1, II, or III water. Type I is
D2777 Practice for Determination of Precision and Bias of
preferred and more commonly used. Type II water was
Applicable Test Methods of Committee D19 on Water
specified at the time of round-robin testing of these test
methods.
These test methods are under the jurisdiction of ASTM Committee D19 on
Water and are the direct responsibility of Subcommittee D19.05 on Inorganic NOTE 1—The user must ensure the type of reagent water is sufficiently
Constituents in Water.
Current edition approved Nov. 1, 2021. Published December 2021. Originally
approved in 1937. Last previous edition approved in 2014 as D511 – 14. DOI: Reagent Chemicals, American Chemical Society Specifications, American
10.1520/D0511-14R21E01. Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or listed by the American Chemical Society, see Annual Standards for Laboratory
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Standards volume information, refer to the standard’s Document Summary page on and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
the ASTM website. MD.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D511 − 14 (2021)
free of interferences.The water should be analyzed using this test method.
minimized by the addition of hydroxylamine and cyanide,
which reduce or complex the metals, or both. Metal concen-
6. Sampling
trations as high as 5 mg/L of iron, 10 mg/L of manganese, 10
6.1 Collect the sample in accordance with Practices D3370.
mg/L of copper, 10 mg/L of zinc, and 10 mg/L of lead can be
tolerated when hydroxylamine and cyanide are added.
6.2 If total recoverable calcium and magnesium concentra-
tions are being determined, acidify the water sample with
9.2 In the titration of calcium plus magnesium, the higher
+2
HNO (sp gr 1.42) to a pH of 2 or less immediately at the time
oxidation states of manganese above Mn react rapidly with
of collection; normally about 2 mL/Lare required.The holding
the indicator to form discolored oxidation products. Hydrox-
time for the samples may be calculated in accordance with
ylamine hydrochloride reagent is used to reduce manganese to
Practice D4841.
the divalent state. The divalent manganese interference can be
eliminated by addition of one or two small crystals of potas-
NOTE 2—Alternatively, the pH may be adjusted in the laboratory if the
sium ferrocyanide.
sample is returned within 14 days. However, acid must be added at least
24hoursbeforeanalysistodissolveanymetalsthatadsorbtothecontainer 9.2.1 Orthophosphate and sulfate ions interfere at concen-
walls. This could reduce hazards of working with acids in the field when
trations in excess of 500 and 10 000 mg/L, respectively.
appropriate.
9.2.2 In the presence of aluminum concentrations in excess
6.3 If dissolved calcium and magnesium concentrations are
of 10 mg/L, the blue color that indicates that the end point has
being determined, filter the samples through a 0.45-µm mem-
been reached will appear and then, on short standing, will
brane filter and acidify with HNO (sp gr 1.42) to a pH of 2 or
revert to red. The reversion should not be confused with the
less immediately at time of collection; normally about 2 mL/L
gradual change that normally takes place in the titrated sample
are required.
several minutes after the titration has been completed.
6.4 A number of sources of calcium contamination have
9.3 In the titration of calcium, ammonium purpurate reacts
beenencounteredinlaboratories.Amongthemostcommonare
with strontium but not with magnesium or barium. However,
plastic ware, paper towels, and dust. Rinsing plastic ware with
the end point in the presence of strontium is sluggish, and the
sample prior to use, avoiding contact of apparatus with paper
titrationisnotstrictlystoichiometric.Bariumdoesnottitrateas
towels,andkeepingexposuretotheairtoaminimumwilllimit
calcium, but affects the indicator in some unknown way so that
the possibility of contamination.
no end point, or at best a poor end point, is obtained. Barium
can be removed by prior precipitation with sulfuric acid, but
TEST METHOD A—COMPLEXOMETRIC
care must be exercised to prevent precipitation of calcium.
TITRATION
Orthophosphate will precipitate calcium at the pH of the test.
7. Scope 9.4 A possible interference from the commonly used
polyphosphates, organic phosphonates, and EDTA/NTA com-
7.1 This test method is applicable to most waters in a range
pounds in water treatment should be recognized.
from 1 to 1000 mg/L of calcium plus magnesium expressed as
calcium, but may fail in the analysis of highly colored waters,
10. Apparatus
brines, or waters that contain excessive amounts of metals.The
10.1 Titration Assembly—Some analysts prefer to use con-
upper and lower limits may be extended by either dilution or
ventionallightingandhandstirring.Othersreportbetterresults
use of micro apparatus.
by using a visual-titration assembly consisting of a motor-
7.2 Data are not available to determine which matrices were
driven stirrer, 25-mL burette, white-porcelain-base burette
used to obtain the precision and bias data, and it is the
holder, and shaded incandescent lamp. The sample beaker is
responsibility of the analyst to determine the acceptability of
placed near the front of the porcelain base and the reaction is
this test method for the matrix being analyzed.
viewed diagonally downward through the side of the beaker
and against the white background. Illumination is from behind
8. Summary of Test Method
the beaker. The capacity of the burette, type lighting, and
8.1 EDTA (ethylenediamine tetraacetic acid or its salts) is
background color may be varied depending on the ionic
added to a sample containing calcium and magnesium ions
concentrations normally encountered and the indicator chosen.
after the pH of the solution is adjusted to 10 for the determi-
10.2 pH Meter, with expanded mV scale.
nation of calcium and magnesium or from pH 12 to 13 for the
determination of calcium alone.The EDTAinitially complexes
11. Reagents and Materials
thecalciumandthenthemagnesium.Theendpointisobserved
by the use of a suitable indicator. At a pH of 12 to 13
11.1 Buffer Solution, Ammonium Chloride-Ammonium
magnesium is precipitated. Magnesium is determined by the
Hydroxide—Dissolve 67.6 g of ammonium chloride (NH Cl)
difference between an aliquot titrated at pH 10 and one titrated
in 200 mL of water. Add 570 mL of concentrated ammonium
at pH 12 to 13.
hydroxide (NH OH, sp gr 0.900). Add 5.00 g of magnesium
salt of EDTA and dilute to 1000 mL. Store in a tightly
9. Interferences
stoppered plastic bottle to prevent the loss of ammonia.
9.1 EDTA reacts with iron, manganese, copper, zinc, lead, Discard the solution when 1 mLadded to a neutralized sample
cobalt, nickel, barium, strontium, calcium, magnesium, and fails to produce a pH of 10.0 6 0.1 at the titration end point.
several other metals. The interference of heavy metals is To attain highest accuracy, adjust the magnesium level to exact
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D511 − 14 (2021)
equivalencethroughtheappropriateadditionofasmallamount Material such as fine-textured, acid-washed, ashless paper, or
of either disodium EDTA or magnesium sulfate (MgSO ). glass fiber paper are acceptable. The user must first ascertain
that the filter paper is of sufficient purity to use without
11.2 Calcium Indicator Solution:
adversely affecting the bias and precision of the test method.
11.2.1 Ammonium Purpurate—Mix thoroughly 1.0 g of
ammonium purpurate with 200 g of sucrose. Place in a bottle
12. Procedure
provided with a dispensing spoon of 0.2-g capacity.
11.2.2 Fluorescein Methylene Iminodiacetic Acid —Grind
12.1 Calcium Plus Magnesium:
0.2 g of fluorescein methylene iminodiacetic acid and 0.12 g of 12.1.1 Measure 100.0 mL of a well-mixed acidified sample
thymolphthalein with 20 g of potassium chloride to 40 to 50
(see 6.2) into a 125-mL beaker or flask.
mesh size. Place in a bottle provided with a dispensing spoon
NOTE 4—If only dissolved calcium plus magnesium is to be
of 0.2-g capacity.
determined, omit 12.1.1 through 12.1.4 and proceed to 12.1.5.
11.3 Calcium Solution, Standard (1.00 mL = 0.400 mg
12.1.2 Add 5 mL of hydrochloric acid (HCl, sp gr 1.19) to
calcium)—Suspend 1.000 g of calcium carbonate (CaCO ),
3 each sample.
driedat180°Cfor1.0hbeforeweighing,inapproximately600
12.1.3 Heatthesamplesonasteambathorhotplateuntilthe
mLof water and dissolve cautiously with a minimum of dilute
volume has been reduced to 15 to 20 mL, making certain that
HCl. Dilute to 1000 mL with water in a volumetric flask.
the samples do not boil.
11.3.1 Alternatively, certified calcium stock solutions of
NOTE 5—For samples with high levels of dissolved or suspended
appropriate known purity are commercially available through
matter, the amount of reduction in volume is left to the discretion of the
chemical supply vendors and may be used.
analyst.
11.4 Chrome Black T Solution (4.0 g/L)—Dissolve 0.4 g of
12.1.4 Cool and filter the samples through a suitable filter
Chrome Black T in 100 mL of water. This solution has a shelf
(such as fine-textured, acid-washed, ashless paper) into
life of approximately 1 week. Alternatively, a dry powder
100-mL volumetric flasks. Wash the paper two or three times
mixture composed of 0.5 g of dye and 100 g of powdered
with water and bring to the volume.
sodium chloride may be used. Store this in a dark-colored
12.1.5 Measure 50 mL of the filtered sample (50.00-mL
bottleprovidedwithadispensingspoonofapproximately0.2-g
maximum) into a 150-mL beaker and adjust the volume to
capacity. The shelf life is at least 1 year.
approximately50mL.AdjustthepHto7to10bythedropwise
addition of ammonium hydroxide (NH OH, sp gr 0.900).
NOTE 3—Chrome Black T is also known as Eriochrome Black T.
11.5 EDTA Solution, Standard (0.01 M, 1 mL = 0.401 mg NOTE 6—For analysis of brines an appropriate aliquot size often can be
determined from knowledge of the specific gravity, for example:
calcium or 0.243 mg magnesium)—Dissolve 3.72 g of
1.000 to 1.025, use 25 mL
Na EDTA dihydrate, which has been dried overnight over
1.025 to 1.050, use 10 mL
H SO in a desiccator, in water (or at 80°C. for 1 hour) and
2 4
1.050 to 1.090, use 5 mL
dilute to 1000 mL in a volumetric flask. The reagent is stable
1.090 to 1.120, use 1 mL
1.120 to 1.180, use 0.1 mL
for several weeks. Check the titer of the reagent by titrating
25.00 mL of CaCO standard solution as described in the
12.1.6 Insert the beaker in the titration assembly and start
procedure for sample analysis.
the stirrer.
12.1.7 Add 1 mL of NH OH·HCl solution (11.6).
11.6 Hydroxylamine Hydrochloride Solution (30 g/L)—
12.1.8 Add 1 mL of buffer solution (11.1). Measure the pH
Dissolve 30 g of hydroxylamine hydrochloride (NH OH·HCl)
and verify that it falls in the pH range from 10.0 + 0.1.Adjust
in water and dilute to 1000 mL.
by the dropwise addition of ammonium hydroxide.
11.7 Potassium Ferrocyanide—(K Fe(CN) ·3H O).
4 6 2
12.1.9 Add 2 mL of NaCN solution (11.8). (Warning—
11.8 Sodium Cyanide Solution (25 g/L)—Dissolve 25 g of Sodium cyanide is a deadly poison. Do not add NaCN t
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