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: C25 − 19

Standard Test Methods for

Chemical Analysis of Limestone, Quicklime, and Hydrated
Lime1
This standard is issued under the fixed designation C25; 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 Insoluble Matter Other Than Silicon Dioxide 11

Loss on Ignition 19
1.1 These test methods cover the chemical analysis of Magnesium Oxide 18
high-calcium and dolomitic limestone, quicklime, and hy- Manganese:
drated lime. These test methods are classified as either standard Bismuthate Method Appendix X4
Periodate (Photometric) Method 27
(preferred) or alternative (optional). pH Determination of Alkaline Earth Solutions 34
Phosphorus:
1.2 The standard test methods are those that employ classi- Titrimetric Method Appendix X3
cal gravimetric or volumetric analytical procedures and are Molybdovanadate Method 26
typically those required for referee analyses where chemical Silicon Dioxide 10
Strontium Oxide Appendix X2
specification requirements are an essential part of contractual Sulfur Trioxide 23
agreement between buyer and seller. Total Carbon:

iTeh Standards
1.3 Alternative or optional test methods are provided for
those who wish to use procedures shorter or more convenient
Direct Combustion-Thermal Conductivity Cell
Method
Total Carbon and Sulfur:
32

(https://standards.iteh.ai)
than the standard methods for the routine determinations of Combustion ⁄Infrared Detection Method 35
Total Iron:
certain constituents. Optional test methods may sometimes be Standard Method, Potassium Dichromate 13
preferred to the standard test methods, but frequently the use of
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Titration
modern and expensive instrumentation is indicated which may Potassium Permanganate Titration Method Appendix X1
Ortho-Phenanthroline, Photometric Method 14
not be accessible to everyone. Therefore, the use of these test Total Sulfur:
methods must be left to the discretion of each laboratory. Sodium Carbonate Fusion 24
Combustion-Iodate Titration Method 25
ASTM
1.4 The analytical procedures appear in the following C25-19
order: Unhydrated Oxides 30
/catalog/standards/astm/90207cb3-a8cb-45c1-aae4-858a45436ece/astm-c25-19
Section 1.5 This standard does not purport to address all of the
Aluminum Oxide 15 safety concerns, if any, associated with its use. It is the
Available Lime Index 28
Calcium and Magnesium Oxide: responsibility of the user of this standard to establish appro-
Alternative EDTA Titration Method 31 priate safety, health, and environmental practices and deter-
Calcium Carbonate Equivalent 33 mine the applicability of regulatory limitations prior to use.
Calcium Oxide:
Gravimetric Method 16 For specific precautionary statements, see 9.3, 10.2.1, 18.4.3,
Volumetric Method 17 31.6.4.2, X2.3.1, and X5.4.1.1.
Carbon Dioxide by Standard Method 22 1.6 This international standard was developed in accor-
Combined Oxides of Iron and Aluminum 12
Ferrous Iron Appendix X5 dance with internationally recognized principles on standard-
Free Calcium Oxide Appendix X6 ization established in the Decision on Principles for the
Free Moisture in Hydrated Lime 21
Free Moisture in Limestone 20
Development of International Standards, Guides and Recom-
Free Silica 29 mendations issued by the World Trade Organization Technical
Insoluble Matter Including Silicon Dioxide: Barriers to Trade (TBT) Committee.
Standard Method 8
Optional Perchloric Acid Method 9
2. Referenced Documents
2.1 ASTM Standards:2
1
These test methods are under the jurisdiction of ASTM Committee C07 on
Lime and Limestone and are the direct responsibility of Subcommittee C07.05 on
2
Chemical Tests. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2019. Published July 2019. Originally approved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1919. Last previous edition approved in 2017 as C25 – 17. DOI: 10.1520/C0025- Standards volume information, refer to the standard’s Document Summary page on
19. the ASTM website.

Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States

1
 C25 − 19
C50/C50M Practice for Sampling, Sample Preparation, be capable of reproducing weighings within 0.0002 g with an
Packaging, and Marking of Lime and Limestone Products accuracy of 60.0002 g. Rapid weighing devices that may be
C51 Terminology Relating to Lime and Limestone (as Used provided such as a chain, damper, or heavy riders shall not
by the Industry) increase the basic inaccuracy by more than 0.0001 g at any
C911 Specification for Quicklime, Hydrated Lime, and reading and with any load within the rated capacity of the
Limestone for Selected Chemical and Industrial Uses balance.
D1193 Specification for Reagent Water 5.1.2 Weights—Weights used for analysis shall conform to
E29 Practice for Using Significant Digits in Test Data to Class S-1 requirements of the National Institute of Standards
Determine Conformance with Specifications and Technology as described in NIST Circular 547.4 They shall
E50 Practices for Apparatus, Reagents, and Safety Consid- be checked at least once a year or when questioned, and
erations for Chemical Analysis of Metals, Ores, and adjusted to within allowable tolerances for Class S-1 weights.
Related Materials All new sets of weights purchased shall have the weights of 1 g
E70 Test Method for pH of Aqueous Solutions With the and larger made of stainless steel or other corrosion-resistant
Glass Electrode alloy not requiring protective coating and shall meet the
E173 Practice for Conducting Interlaboratory Studies of density requirements for Class S.
Methods for Chemical Analysis of Metals (Withdrawn 5.1.3 Glassware and Laboratory Containers—Standard
1997)3 volumetric flasks, burets, pipets, dispensers, and so forth, shall
E177 Practice for Use of the Terms Precision and Bias in be carefully selected precision grade or better and shall be
ASTM Test Methods calibrated, if necessary, to meet the requirements of each
E200 Practice for Preparation, Standardization, and Storage operation. Standard-type interchangeable ground glass or TFE-
of Standard and Reagent Solutions for Chemical Analysis fluorocarbon joints are recommended for all volumetric glass-
E691 Practice for Conducting an Interlaboratory Study to ware. Polyethylene containers are recommended for all aque-
Determine the Precision of a Test Method ous solutions of alkalies and for standard solutions where the
E832 Specification for Laboratory Filter Papers presence of dissolved silica or alkali from the glass would be
objectionable.
3. Terminology
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3.1 Definitions:Definitions—Unless otherwise specified, for
5.1.4 Desiccators—Desiccators shall be provided with a
good desiccant such as anhydrous magnesium perchlorate,

Terminology C51. (https://standards.iteh.ai)

definitions of terms used in these test methods refer to activated alumina, sulfuric acid, or phosphoric anhydride.
Anhydrous calcium sulfate may also be used provided it has
been treated with a color-changing indicator to show when the
4. Significance and Use
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4.1 These test methods provide accurate and reliable ana-
desiccant has lost its effectiveness. Calcium chloride and silica
gel are not satisfactory desiccants for this type of analysis.
lytical procedures to determine the chemical constituents of 5.1.5 Filter Paper—Filter paper shall conform to the re-
limestone, quicklime, and hydrated lime (see NoteASTM quirements
C25-19
1). The of Specification E832, Type II (quantitative). Class
percentages of specific constituents which determine a materi- E shall be used for coarse and gelatinous precipitates. When
al’s quality or /catalog/standards/astm/90207cb3-a8cb-45c1-aae4-858a45436ece/astm-c25-19
fitness for use are of significance depending medium-textured paper is required, Class F filter paper shall be
upon the purpose or end use of the material. Results obtained used. When a retentive paper is needed, Class G shall be used.
may be used in relation to specification requirements. Recommendations:
Class Filter Pore Size (µm) Filter Speed
4.2 Because quicklime and hydrated lime quickly absorb E 20 to 25 fast speed
water and carbon dioxide from the air, precision and bias are F 8 medium speed
G 2.5 slow speed
extremely dependent upon precautions taken during sample
preparation and analysis to minimize excessive exposure to 5.1.6 Crucibles—Platinum crucibles and tight fitting lids
ambient conditions. should preferably be made of pure unalloyed platinum and be
of 25 to 35-mL capacity. Where alloyed platinum is used for
NOTE 1—These test methods can be applied to other calcareous
materials if provisions are made to compensate for known interferences.
greater stiffness or to obviate sticking of fused material to
crucible or lid, the alloyed platinum should not decrease in
5. General Apparatus and Materials and Reagents weight by more than 0.2 mg when heated at 1200 °C for 1 h.
5.1 General Apparatus and Materials: 5.1.7 Muffle Furnace—The electric muffle furnace should be
5.1.1 Balance—The balance shall be of an analytical type capable of continuous operation up to 1000 °C and be capable
with a capacity not to exceed 200 g. It may be of conventional of intermittent operation at higher temperatures if required. It
design or it may be a constant-load, direct-reading type. It shall should have an indicating pyrometer accurate to 625 °C.

3 4
The last approved version of this historical standard is referenced on Available from National Institute of Standards and Technology (NIST), 100
www.astm.org. Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.

2
 C25 − 19
5.2 Reagents: 6.2 Tared or Weighed Crucibles—The tare weight of cru-
5.2.1 Purity of Reagents—Reagent grade chemicals shall be cibles shall be determined by preheating the empty crucible to
used in all tests. Unless otherwise indicated, it is intended that constant weight at the same temperature and under the same
all reagents shall conform to the specifications of the Commit- conditions as shall be used for the final ignition of a residue and
tee on Analytical Reagents of the American Chemical Society5 cooling in a desiccator for the same period of time used for the
where such specifications are available. Other grades may be crucible containing the residue.
used provided it is first ascertained that the reagent is of 6.3 Constancy of Weight of Ignited Residue—To definitely
sufficiently high purity to permit its use without lessening the establish the constancy of weight of the ignited residue, the
accuracy of the determination. In addition to this, it is desirable residue and container shall be ignited at the specified tempera-
in many cases for the analyst to ensure the accuracy of his ture and time, cooled to room temperature in a desiccator, and
results by running blanks or checking against a comparable weighed. The residue and container shall then be reheated for
sample of known composition. at least 30 min at the same temperature, cooled in a desiccator
5.2.2 Purity of Water—Unless otherwise indicated, refer- for the same period of time, and reweighed. Additional ignition
ences to water are understood to mean distilled water or other periods may be required until two consecutive weights do not
water of equivalent purity. Water conforming to Specification differ by more than 0.2 mg, at which time it shall be considered
D1193 meets these requirements. that constant weight has been attained. For ignition loss, each
5.2.3 Concentration of Reagents: reheating period shall be 5 min.
5.2.3.1 Concentrated Acids and Ammonium Hydroxide—
When acids and ammonium hydroxide are specified by name 6.4 Calculation:
or chemical formula only, it shall be understood that concen- 6.4.1 The calculations included in the individual procedures
trated reagents approximating the following specific gravities sometimes assume that the exact weight specified has been
or concentrations are intended: used. Accurately weighed samples which are approximately
Acetic acid (HC2H3O2) 99.5 %
but not exactly equal to the weight specified may be used
Hydrochloric acid (HCl) sp gr 1.19 provided appropriate corrections are made in the calculation.
Hydrofluoric acid (HF) 48 % Unless otherwise stated, weights of all samples and residues

iTeh Standards
Nitric acid (HNO3) sp gr 1.42
Perchloric acid (HClO4) 70 % should be recorded to the nearest 0.0001 g.
Phosphoric acid (H3PO4) 85 % 6.4.2 In all mathematical operations on a set of observed

(https://standards.iteh.ai)
Sulfuric acid (H2SO4) sp gr 1.84 values, the equivalent of two more places of figures than in the
Ammonium hydroxide (NH4OH) sp gr 0.90
single observed values shall be retained. For example, if
5.2.3.2 Dilute Reagents—The concentration of dilute acids observed values are read or determined to the nearest 0.1 mg,
4
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stating the number of measured volumes of the concentrated Preview
and NH OH except when standardized, are specified as a ratio carry numbers to the nearest 0.001 mg in calculation.
6.5 Rounding Figures—Rounding figures to the nearest
reagent to be diluted with a given number of measured volumes
of water. In conformance with international practice, new and significant place required in the report should be done after the
revised methods will use the “plus” designation instead ASTM of theC25-19
calculations are completed, in order to keep the final results
ratio (:) symbol as the specified designation of dilution; for free from calculation errors. The rounding procedure should
/catalog/standards/astm/90207cb3-a8cb-45c1-aae4-858a45436ece/astm-c25-19
example, H2SO4 (5 + 95) means 5 volumes of concentrated follow the principle outlined in Practice E29.
H2SO4 (sp gr 1.84) diluted with 95 volumes of water.
5.2.3.3 Standard Solutions—Concentrations of standard so- 7. Performance Requirements for Test Methods
lutions shall be expressed as normalities (N) or as equivalents 7.1 Referee Analyses—The reference test methods that ap-
in grams per millilitre of the component to be determined, for pear in Sections 8 through 32, or any other test methods
example: 0.1 N K2Cr2O7 solution (1 mL = 0.004 g Fe2O3). The qualified in accordance with 7.3, are required for referee
average of at least three determinations shall be used for all analysis in those cases where conformance to the requirements
standardizations. The standardization used to determine the of a chemical specification are questioned. In these cases a
strength of the standard solutions is described in the text under limestone, quicklime, or hydrated lime shall not be rejected for
each of the appropriate procedures. failure to conform to chemical requirements unless all sample
preparation and analysis of any one constituent is made entirely
6. General Procedures by reference test methods prescribed in the appropriate sections
6.1 Sampling—Samples of lime and limestone for chemical of this test method or by other qualified test methods. Excep-
analysis shall be taken and prepared in accordance with the tion can be made when specific test methods are prescribed in
requirements of Practice C50/C50M applicable to the material the standard specification for the limestone, quicklime, or
to be tested. hydrated lime in question. The test methods actually used for
the analysis shall be designated.
7.1.1 When there is a question regarding acceptance, referee
5
Reagent Chemicals, American Chemical Society Specifications, American analyses shall be made in duplicate. If the two results do not
Chemical Society, Washington, DC. For suggestions on the testing of reagents not agree within the permissible variation given in Table 1, the
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
determination including sample preparation shall be repeated
and National Formulary, U.S. Pharmacopeia Convention, Inc. (USPC), Rockville, in duplicate until the results agree within the permissible
MD. variation. When the results agree within the permissible

3
 C25 − 19
TABLE 1 Maximum Permissible Variations in ResultsA hydration or carbonation with sealed containers and desiccation during
(Column 1) (Column 2) (Column 3) cooling. Carbon and sulfur may be driven off during heating, rendering the
Maximum Difference of converted CRM unsuitable as a standard for carbon and sulfur determi-
Constituent
Maximum Difference the Average of nations. For carbon and sulfur determinations use the appropriate CRM in
Between Duplicates Duplicates from CRM its normal matrix.
Certificate ValuesB
Al as Al2O3 0.20 ±0.30 7.1.4 The average of the results of acceptable duplicate
Ca as CaO 0.20 ±0.30 determinations for each constituent may differ from the CRM
Mg as MgO 0.20 ±0.30
C (lime and hydrated 0.20 ±0.30 certificate value by no more than the value shown in Column
lime) 3 of Table 1. When no CRM certificate value is given, a
C (limestone) 0.60 ±0.60 generally accepted accuracy standard for that constituent has
Fe as Fe2O3 0.10 ±0.15
Si as SiO2 0.15 ±0.30 not been identified. In such cases, only the differences between
Mn 0.05 ±0.10 duplicate values as specified in 7.1.3 shall apply and notifica-
P 0.02 ±0.05 tion of this exception shall be reported.
C
Sr as SrO 0.05
S 0.03 ±0.05 7.1.5 In questions concerning the acceptance or rejection of
A
For demonstrating the performance of rapid test methods the CRM closest in
a limestone, quicklime, or hydrated lime product, upon request
overall composition to the limestone shall be used (see Table 2). In the case of data shall be made available to all parties involved demonstrat-
quicklime or hydrated lime, the CRM closest in overall composition, after heating ing that precise and accurate results were obtained with CRM
at 1000 °C for 1 h, to the product composition shall be used, except for C and S
determinations (see Note 3). samples by the same analyst making the acceptance determi-
B
Interelement corrections may be used for any standardization provided improved nation.
accuracy can be demonstrated.
C
No CRM currently available. 7.2 Optional Analyses—The alternative test methods, as
opposed to reference methods, provide procedures that are, in
some cases, shorter or more convenient to use for routine
determination of some constituents (see Note 4). In some
variation, their average shall be accepted as the correct value.
instances longer, more complex procedures have been retained
For the purpose of comparing results, the percentages shall be
as alternative test methods to permit comparison of results by
iTeh Standards
calculated to one more significant figure than reported as
different procedures or for use when unusual materials are
indicated in the test methods. When a blank determination is
being examined, or when unusual preparation for analysis is
specified, one shall be made with each individual analysis or
(https://standards.iteh.ai)
required. Results from alternative test methods may be used as
with each group of two or more samples analyzed on the same
a basis for acceptance or rejection.
day for a given constituent.

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7.1.2 Test results from Referee methods intended for use as
a basis for product acceptance or rejection, or for manufactur-
er’s certification, can be used only after demonstration of
NOTE 4—It is not intended that the use of reference test methods be
confined to referee analysis. A reference test method may be used in
preference to an alternative test method when so desired. A reference test
method must be used where an alternative test method is not provided.
precise and accurate analyses by meeting the requirements of
7.1.3, or except when demonstrated under 7.3.2.1. Such ASTM dem- C25-197.2.1 Duplicate analyses and blank determinations are left
to the discretion of the analyst when using the alternative test
onstrations may /catalog/standards/astm/90207cb3-a8cb-45c1-aae4-858a45436ece/astm-c25-19
be made concurrently with analysis of the
limestone, quicklime, or hydrated lime product being tested. methods. The final results should include the number of
The demonstration is required only for those constituents being determinations performed and whether or not they were
used as a basis for acceptance, rejection, or certification of a corrected for blank values.
limestone, quicklime, or hydrated lime, but may be made for 7.3 Performance Requirements for Alternative Test Meth-
any constituent of limestone, quicklime, or hydrated lime ods:
product for which a standard exists. Such demonstrations must 7.3.1 Definition and Scope—When analytical data obtained
be made annually. in accordance with this section is required, any test method
7.1.3 Demonstrations shall be made by analysis of each may be used that meets the requirements of 7.3.2. A test
constituent of concern in a CRM limestone, quicklime, or method is considered to consist of the specific procedures,
hydrated lime (see Notes 2 and 3). Duplicate samples shall be reagents, supplies, equipment, instrument, and so forth, se-
run on different days. The same test methods to be used for lected and used in a consistent manner by a specific laboratory.
analysis of the limestone, quicklime, or hydrated lime being 7.3.1.1 If more than one instrument is used for the same
tested shall be used for analysis of the CRM. If the duplicate analysis, use of each instrument shall constitute a separate test
results do not agree within the permissible variation given in method and each must be qualified separately.
Table 1, the determinations shall be repeated, following iden- 7.3.2 Qualification of a Test Method—Prior to use each test
tification and correction of problems or errors, until a set of method (see 7.3.1) must be qualified for each material that will
duplicate results do agree within the permissible variation. be tested. Qualification data or, if applicable, requalification
NOTE 2—The term CRM refers to approved Certified Reference data shall be made available.
Materials listed in Table 2. 7.3.2.1 Using the test method chosen, make single determi-
NOTE 3—There are no CRMs that are quicklime or hydrated lime as nations for each constituent under consideration on the CRM
supplied. When analyzing a quicklime or hydrated lime the CRM in
carbonate form needs to be converted to closely resemble the matrix of the which in overall composition most closely resembles the
product being tested. To accomplish this conversion, heat the chosen CRM limestone, quicklime, or hydrated lime to be tested (see Note
for 1 h at 1000 °C, immediately prior to analysis and protect it from 2). Complete two rounds of tests on nonconsecutive days