ASTM C25-19e1

Standard Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime

SIGNIFICANCE AND USE
4.1 These test methods provide accurate and reliable analytical procedures to determine the chemical constituents of limestone, quicklime, and hydrated lime (see Note 1). The percentages of specific constituents which determine a material's quality or fitness for use are of significance depending upon the purpose or end use of the material. Results obtained may be used in relation to specification requirements.  
4.2 Because quicklime and hydrated lime quickly absorb water and carbon dioxide from the air, precision and bias are extremely dependent upon precautions taken during sample preparation and analysis to minimize excessive exposure to ambient conditions.  
Note 1: These test methods can be applied to other calcareous materials if provisions are made to compensate for known interferences.
SCOPE
1.1 These test methods cover the chemical analysis of high-calcium and dolomitic limestone, quicklime, and hydrated lime. These test methods are classified as either standard (preferred) or alternative (optional).  
1.2 The standard test methods are those that employ classical gravimetric or volumetric analytical procedures and are typically those required for referee analyses where chemical specification requirements are an essential part of contractual agreement between buyer and seller.  
1.3 Alternative or optional test methods are provided for those who wish to use procedures shorter or more convenient than the standard methods for the routine determinations of certain constituents. Optional test methods may sometimes be preferred to the standard test methods, but frequently the use of modern and expensive instrumentation is indicated which may not be accessible to everyone. Therefore, the use of these test methods must be left to the discretion of each laboratory.  
1.4 The analytical procedures appear in the following order:    
Section    
Aluminum Oxide  
15  
Available Lime Index  
28    
Calcium and Magnesium Oxide:  
Alternative EDTA Titration Method  
31  
Calcium Carbonate Equivalent  
33    
Calcium Oxide:  
Gravimetric Method  
16    
Volumetric Method  
17    
Carbon Dioxide by Standard Method  
22    
Combined Oxides of Iron and Aluminum  
12    
Ferrous Iron  
Appendix X5  
Free Calcium Oxide  
Appendix X6    
Free Moisture in Hydrated Lime  
21    
Free Moisture in Limestone  
20    
Free Silica  
29  
Insoluble Matter Including Silicon Dioxide:    
Standard Method  
8    
Optional Perchloric Acid Method  
9  
Insoluble Matter Other Than Silicon Dioxide  
11    
Loss on Ignition  
19  
Magnesium Oxide  
18  
Manganese:    
Bismuthate Method  
Appendix X4    
Periodate (Photometric) Method  
27    
pH Determination of Alkaline Earth Solutions  
34    
Phosphorus:    
Titrimetric Method  
Appendix X3    
Molybdovanadate Method  
26  
Silicon Dioxide  
10  
Strontium Oxide  
Appendix X2    
Sulfur Trioxide  
23    
Total Carbon:    
Direct Combustion-Thermal Conductivity Cell
Method  
32  
Total Carbon and Sulfur:    
Combustion/Infrared Detection Method  
35    
Total Iron:    
Standard Method, Potassium Dichromate
Titration  
13    
Potassium Permanganate Titration Method  
Appendix X1  
Ortho-Phenanthroline, Photometric Method  
14  
Total Sulfur:    
Sodium Carbonate Fusion  
24  
Combustion-Iodate Titration Method  
25  
Unhydrated Oxides  
30  
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.
For specific precautionary statements, see 9.3, 10.2.1, 18.4.3, 31.6.4.2, X2.3.1, and X5.4.1.1.  
1.6 This international standard was developed...

General Information

• Status: Published
• Publication Date: 30-Apr-2019
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: C07 - Lime and Limestone
• Drafting Committee: C07.05 - Chemical Tests

Relations

• Replaces: ASTM C25-19 - Standard Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime
• Effective Date: 01-May-2019
• Referred By: ASTM C1529-19 - Standard Specification for Quicklime, Hydrated Lime, and Limestone for Environmental Uses
• Effective Date: 01-May-2019
• Referred By: ASTM D5050-08(2023) - Standard Guide for Commercial Use of Lime Kiln Dusts and Portland Cement Kiln Dusts
• Effective Date: 01-May-2019
• Referred By: ASTM C706-19 - Standard Specification for Limestone for Animal Feed Use
• Effective Date: 01-May-2019
• Referred By: ASTM C1097-19 - Standard Specification for Hydrated Lime for Use in Asphalt Cement or Bituminous Paving Mixtures
• Effective Date: 01-May-2019
• Referred By: ASTM C1318-15a(2020) - Standard Test Method for Determination of Total Neutralizing Capability and Dissolved Calcium and Magnesium Oxide in Lime for Flue Gas Desulfurization (FGD)
• Effective Date: 01-May-2019
• Referred By: ASTM C593-19 - Standard Specification for Fly Ash and Other Pozzolans for Use With Lime for Soil Stabilization
• Effective Date: 01-May-2019
• Referred By: ASTM C1164-22 - Standard Practice for Evaluation of Limestone or Lime Uniformity From a Single Source
• Effective Date: 01-May-2019
• Referred By: ASTM D1301-91(2020) - Standard Test Methods for Chemical Analysis of White Lead Pigments
• Effective Date: 01-May-2019
• Referred By: ASTM C1489-15(2022) - Standard Specification for Lime Putty for Structural Purposes
• Effective Date: 01-May-2019
• Referred By: ASTM C114-23 - Standard Test Methods for Chemical Analysis of Hydraulic Cement
• Effective Date: 01-May-2019
• Referred By: ASTM D1199-86(2020) - Standard Specification for Calcium Carbonate Pigments
• Effective Date: 01-May-2019
• Referred By: ASTM F3339-20 - Standard Guide for Construction or Renovation of Native-soil Athletic Fields
• Effective Date: 01-May-2019
• Referred By: ASTM C1271-99(2020) - Standard Test Method for X-ray Spectrometric Analysis of Lime and Limestone
• Effective Date: 01-May-2019
• Referred By: ASTM C1797-23a - Standard Specification for Ground Calcium Carbonate and Aggregate Mineral Fillers for use in Hydraulic Cement Concrete
• Effective Date: 01-May-2019

Overview

ASTM C25-19e1 - Standard Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime outlines comprehensive procedures for accurately determining the chemical constituents of high-calcium and dolomitic limestone, quicklime, and hydrated lime. Developed by ASTM International, this standard is widely recognized for providing reliable methodologies essential in quality assurance, contractual compliance, and specification conformance across diverse industrial and construction applications. The standard encompasses both classical (gravimetric and volumetric) and modern, alternative instrumental methods, offering flexibility to laboratories with differing analytical capabilities.

Key Topics

• Scope of Analysis: The standard covers methods suitable for both high-calcium and dolomitic forms of materials, accommodating a variety of lime and limestone products.
• Analytical Methods: Includes both preferred standard methods (for referee analyses) and alternative (optional) methods that may use advanced instrumentation for faster or more convenient analysis.
• Constituents Measured: The test methods allow for the quantitative determination of crucial components such as:
  • Aluminum oxide, calcium oxide, magnesium oxide, iron oxide, silicon dioxide, sulfur trioxide, strontium oxide, and more.
  • Free calcium oxide, available lime index, loss on ignition, free moisture, calcium carbonate equivalent, total carbon, and total sulfur.
• Quality Assurance: Emphasizes the need for precision and accuracy by requiring duplicate analyses and comparison with certified reference materials (CRMs) for key constituents.
• Material Handling and Sample Preparation: Highlights the importance of minimizing ambient exposure, especially for quicklime and hydrated lime, due to their reactivity with water and carbon dioxide in the air.
• Safety and Compliance: Users must consider appropriate safety, health, and environmental practices and conform to regulatory guidelines when using chemicals and laboratory equipment.

Applications

• Construction Materials Quality Control: Essential for producers and users of building stones, concrete, cement, and lime-based products to verify material composition and meet project specifications.
• Industrial Processes: Enables manufacturers in sectors such as steel, environmental, and chemical processing to monitor raw material purity and adjust feedstocks accordingly.
• Contractual Verification: Serves as the basis for acceptance, rejection, or certification of lime and limestone products in procurement and supply chain agreements.
• Research and Development: Provides benchmark methods for laboratories developing new materials or optimizing existing lime and limestone products.
• Regulatory Compliance: Supports adherence to both national and international regulations on material content, especially when used as a reference by government or industry agencies.

Related Standards

• ASTM C50/C50M - Practice for Sampling, Sample Preparation, Packaging, and Marking of Lime and Limestone Products
• ASTM C51 - Terminology Relating to Lime and Limestone
• ASTM C911 - Specification for Quicklime, Hydrated Lime, and Limestone for Selected Chemical and Industrial Uses
• ASTM D1193 - Specification for Reagent Water
• ASTM E29 - Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• ASTM E70 - Test Method for pH of Aqueous Solutions with the Glass Electrode
• ASTM E832 - Specification for Laboratory Filter Papers

Conclusion

ASTM C25-19e1 serves a critical role in the chemical analysis of limestone, quicklime, and hydrated lime by establishing standardized, reproducible test methods. Its implementation supports industries in ensuring consistent product quality, meeting contractual and regulatory requirements, and optimizing material performance. The standard is an indispensable resource for laboratories, manufacturers, and end-users dedicated to delivering confidence in lime and limestone product integrity.

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.
´1
Designation: C25 − 19
Standard Test Methods for
Chemical Analysis of Limestone, Quicklime, and Hydrated
Lime
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.
ε NOTE—Editorially added research report to Section 21 in April 2024.
1. Scope
Free Calcium Oxide Appendix X6
Free Moisture in Hydrated Lime 21
1.1 These test methods cover the chemical analysis of
Free Moisture in Limestone 20
high-calcium and dolomitic limestone, quicklime, and hy- Free Silica 29
Insoluble Matter Including Silicon Dioxide:
drated lime. These test methods are classified as either standard
Standard Method 8
(preferred) or alternative (optional).
Optional Perchloric Acid Method 9
Insoluble Matter Other Than Silicon Dioxide 11
1.2 The standard test methods are those that employ classi-
Loss on Ignition 19
cal gravimetric or volumetric analytical procedures and are
Magnesium Oxide 18
Manganese:
typically those required for referee analyses where chemical
Bismuthate Method Appendix X4
specification requirements are an essential part of contractual
Periodate (Photometric) Method 27
agreement between buyer and seller.
pH Determination of Alkaline Earth Solutions 34
Phosphorus:
1.3 Alternative or optional test methods are provided for
Titrimetric Method Appendix X3
those who wish to use procedures shorter or more convenient Molybdovanadate Method 26
Silicon Dioxide 10
than the standard methods for the routine determinations of
Strontium Oxide Appendix X2
certain constituents. Optional test methods may sometimes be
Sulfur Trioxide 23
Total Carbon:
preferred to the standard test methods, but frequently the use of
Direct Combustion-Thermal Conductivity Cell 32
modern and expensive instrumentation is indicated which may
Method
not be accessible to everyone. Therefore, the use of these test
Total Carbon and Sulfur:
Combustion ⁄Infrared Detection Method 35
methods must be left to the discretion of each laboratory.
Total Iron:
1.4 The analytical procedures appear in the following order:
Standard Method, Potassium Dichromate 13
Titration
Section
Potassium Permanganate Titration Method Appendix X1
Aluminum Oxide 15
Ortho-Phenanthroline, Photometric Method 14
Available Lime Index 28
Total Sulfur:
Calcium and Magnesium Oxide:
Sodium Carbonate Fusion 24
Alternative EDTA Titration Method 31
Combustion-Iodate Titration Method 25
Calcium Carbonate Equivalent 33
Unhydrated Oxides 30
Calcium Oxide:
Gravimetric Method 16
1.5 This standard does not purport to address all of the
Volumetric Method 17
safety concerns, if any, associated with its use. It is the
Carbon Dioxide by Standard Method 22
Combined Oxides of Iron and Aluminum 12 responsibility of the user of this standard to establish appro-
Ferrous Iron Appendix X5
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
9.3, 10.2.1, 18.4.3,
1 For specific precautionary statements, see
These test methods are under the jurisdiction of ASTM Committee C07 on
31.6.4.2, X2.3.1, and X5.4.1.1.
Lime and Limestone and are the direct responsibility of Subcommittee C07.05 on
Chemical Tests.
1.6 This international standard was developed in accor-
Current edition approved May 1, 2019. Published July 2019. Originally approved
dance with internationally recognized principles on standard-
in 1919. Last previous edition approved in 2017 as C25 – 17. DOI: 10.1520/C0025-
19E01. ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
C25 − 19
Development of International Standards, Guides and Recom- 5. General Apparatus and Materials and Reagents
mendations issued by the World Trade Organization Technical
5.1 General Apparatus and Materials:
Barriers to Trade (TBT) Committee.
5.1.1 Balance—The balance shall be of an analytical type
with a capacity not to exceed 200 g. It may be of conventional
2. Referenced Documents
design or it may be a constant-load, direct-reading type. It shall
2.1 ASTM Standards:
be capable of reproducing weighings within 0.0002 g with an
C50/C50M Practice for Sampling, Sample Preparation,
accuracy of 60.0002 g. Rapid weighing devices that may be
Packaging, and Marking of Lime and Limestone Products
provided such as a chain, damper, or heavy riders shall not
C51 Terminology Relating to Lime and Limestone (as Used
increase the basic inaccuracy by more than 0.0001 g at any
by the Industry)
reading and with any load within the rated capacity of the
C911 Specification for Quicklime, Hydrated Lime, and
balance.
Limestone for Selected Chemical and Industrial Uses
5.1.2 Weights—Weights used for analysis shall conform to
D1193 Specification for Reagent Water
Class S-1 requirements of the National Institute of Standards
E29 Practice for Using Significant Digits in Test Data to
and Technology as described in NIST Circular 547. They shall
Determine Conformance with Specifications
be checked at least once a year or when questioned, and
E50 Practices for Apparatus, Reagents, and Safety Consid-
adjusted to within allowable tolerances for Class S-1 weights.
erations for Chemical Analysis of Metals, Ores, and
All new sets of weights purchased shall have the weights of 1 g
Related Materials
and larger made of stainless steel or other corrosion-resistant
E70 Test Method for pH of Aqueous Solutions With the
alloy not requiring protective coating and shall meet the
Glass Electrode
density requirements for Class S.
E173 Practice for Conducting Interlaboratory Studies of
5.1.3 Glassware and Laboratory Containers—Standard
Methods for Chemical Analysis of Metals (Withdrawn
volumetric flasks, burets, pipets, dispensers, and so forth, shall
1997)
be carefully selected precision grade or better and shall be
E177 Practice for Use of the Terms Precision and Bias in
calibrated, if necessary, to meet the requirements of each
ASTM Test Methods
operation. Standard-type interchangeable ground glass or TFE-
E200 Practice for Preparation, Standardization, and Storage
fluorocarbon joints are recommended for all volumetric glass-
of Standard and Reagent Solutions for Chemical Analysis
ware. Polyethylene containers are recommended for all aque-
E691 Practice for Conducting an Interlaboratory Study to
ous solutions of alkalies and for standard solutions where the
Determine the Precision of a Test Method
presence of dissolved silica or alkali from the glass would be
E832 Specification for Laboratory Filter Papers
objectionable.
5.1.4 Desiccators—Desiccators shall be provided with a
3. Terminology
good desiccant such as anhydrous magnesium perchlorate,
3.1 Definitions:Definitions—Unless otherwise specified, for activated alumina, sulfuric acid, or phosphoric anhydride.
definitions of terms used in these test methods refer to Anhydrous calcium sulfate may also be used provided it has
Terminology C51. been treated with a color-changing indicator to show when the
desiccant has lost its effectiveness. Calcium chloride and silica
4. Significance and Use
gel are not satisfactory desiccants for this type of analysis.
5.1.5 Filter Paper—Filter paper shall conform to the re-
4.1 These test methods provide accurate and reliable ana-
quirements of Specification E832, Type II (quantitative). Class
lytical procedures to determine the chemical constituents of
E shall be used for coarse and gelatinous precipitates. When
limestone, quicklime, and hydrated lime (see Note 1). The
medium-textured paper is required, Class F filter paper shall be
percentages of specific constituents which determine a materi-
used. When a retentive paper is needed, Class G shall be used.
al’s quality or fitness for use are of significance depending
Recommendations:
upon the purpose or end use of the material. Results obtained
Class Filter Pore Size (μm) Filter Speed
may be used in relation to specification requirements.
E 20 to 25 fast speed
F 8 medium speed
4.2 Because quicklime and hydrated lime quickly absorb
G 2.5 slow speed
water and carbon dioxide from the air, precision and bias are
5.1.6 Crucibles—Platinum crucibles and tight fitting lids
extremely dependent upon precautions taken during sample
should preferably be made of pure unalloyed platinum and be
preparation and analysis to minimize excessive exposure to
of 25 to 35-mL capacity. Where alloyed platinum is used for
ambient conditions.
greater stiffness or to obviate sticking of fused material to
NOTE 1—These test methods can be applied to other calcareous
crucible or lid, the alloyed platinum should not decrease in
materials if provisions are made to compensate for known interferences.
weight by more than 0.2 mg when heated at 1200 °C for 1 h.
5.1.7 Muffle Furnace—The electric muffle furnace should be
2 capable of continuous operation up to 1000 °C and be capable
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.
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.
´1
C25 − 19
of intermittent operation at higher temperatures if required. It 6. General Procedures
should have an indicating pyrometer accurate to 625 °C.
6.1 Sampling—Samples of lime and limestone for chemical
5.2 Reagents: analysis shall be taken and prepared in accordance with the
5.2.1 Purity of Reagents—Reagent grade chemicals shall be requirements of Practice C50/C50M applicable to the material
used in all tests. Unless otherwise indicated, it is intended that to be tested.
all reagents shall conform to the specifications of the Commit-
6.2 Tared or Weighed Crucibles—The tare weight of cru-
tee on Analytical Reagents of the American Chemical Society
cibles shall be determined by preheating the empty crucible to
where such specifications are available. Other grades may be
constant weight at the same temperature and under the same
used provided it is first ascertained that the reagent is of
conditions as shall be used for the final ignition of a residue and
sufficiently high purity to permit its use without lessening the
cooling in a desiccator for the same period of time used for the
accuracy of the determination. In addition to this, it is desirable
crucible containing the residue.
in many cases for the analyst to ensure the accuracy of his
6.3 Constancy of Weight of Ignited Residue—To definitely
results by running blanks or checking against a comparable
establish the constancy of weight of the ignited residue, the
sample of known composition.
residue and container shall be ignited at the specified tempera-
5.2.2 Purity of Water—Unless otherwise indicated, refer-
ture and time, cooled to room temperature in a desiccator, and
ences to water are understood to mean distilled water or other
weighed. The residue and container shall then be reheated for
water of equivalent purity. Water conforming to Specification
at least 30 min at the same temperature, cooled in a desiccator
D1193 meets these requirements.
for the same period of time, and reweighed. Additional ignition
5.2.3 Concentration of Reagents:
periods may be required until two consecutive weights do not
5.2.3.1 Concentrated Acids and Ammonium Hydroxide—
differ by more than 0.2 mg, at which time it shall be considered
When acids and ammonium hydroxide are specified by name
that constant weight has been attained. For ignition loss, each
or chemical formula only, it shall be understood that concen-
reheating period shall be 5 min.
trated reagents approximating the following specific gravities
or concentrations are intended:
6.4 Calculation:
6.4.1 The calculations included in the individual procedures
Acetic acid (HC H O ) 99.5 %
2 3 2
Hydrochloric acid (HCl) sp gr 1.19
sometimes assume that the exact weight specified has been
Hydrofluoric acid (HF) 48 %
used. Accurately weighed samples which are approximately
Nitric acid (HNO ) sp gr 1.42
but not exactly equal to the weight specified may be used
Perchloric acid (HClO ) 70 %
Phosphoric acid (H PO ) 85 %
3 4 provided appropriate corrections are made in the calculation.
Sulfuric acid (H SO ) sp gr 1.84
2 4
Unless otherwise stated, weights of all samples and residues
Ammonium hydroxide (NH OH) sp gr 0.90
should be recorded to the nearest 0.0001 g.
5.2.3.2 Dilute Reagents—The concentration of dilute acids
6.4.2 In all mathematical operations on a set of observed
and NH OH except when standardized, are specified as a ratio
values, the equivalent of two more places of figures than in the
stating the number of measured volumes of the concentrated
single observed values shall be retained. For example, if
reagent to be diluted with a given number of measured volumes
observed values are read or determined to the nearest 0.1 mg,
of water. In conformance with international practice, new and
carry numbers to the nearest 0.001 mg in calculation.
revised methods will use the “plus” designation instead of the
6.5 Rounding Figures—Rounding figures to the nearest
ratio (:) symbol as the specified designation of dilution; for
significant place required in the report should be done after the
example, H SO (5 + 95) means 5 volumes of concentrated
2 4
calculations are completed, in order to keep the final results
H SO (sp gr 1.84) diluted with 95 volumes of water.
2 4
free from calculation errors. The rounding procedure should
5.2.3.3 Standard Solutions—Concentrations of standard so-
follow the principle outlined in Practice E29.
lutions shall be expressed as normalities (N) or as equivalents
in grams per millilitre of the component to be determined, for
7. Performance Requirements for Test Methods
example: 0.1 N K Cr O solution (1 mL = 0.004 g Fe O ). The
2 2 7 2 3
7.1 Referee Analyses—The reference test methods that ap-
average of at least three determinations shall be used for all
pear in Sections 8 through 32, or any other test methods
standardizations. The standardization used to determine the
qualified in accordance with 7.3, are required for referee
strength of the standard solutions is described in the text under
analysis in those cases where conformance to the requirements
each of the appropriate procedures.
of a chemical specification are questioned. In these cases a
limestone, quicklime, or hydrated lime shall not be rejected for
failure to conform to chemical requirements unless all sample
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
preparation and analysis of any one constituent is made entirely
listed by the American Chemical Society, see Analar Standards for Laboratory
by reference test methods prescribed in the appropriate sections
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
of this test method or by other qualified test methods. Excep-
and National Formulary, U.S. Pharmacopeia Convention, Inc. (USPC), Rockville,
MD. tion can be made when specific test methods are prescribed in
´1
C25 − 19
the standard specification for the limestone, quicklime, or Table 1, the determinations shall be repeated, following iden-
hydrated lime in question. The test methods actually used for tification and correction of problems or errors, until a set of
the analysis shall be designated. duplicate results do agree within the permissible variation.
7.1.1 When there is a question regarding acceptance, referee
NOTE 2—The term CRM refers to approved Certified Reference
analyses shall be made in duplicate. If the two results do not
Materials listed in Table 2.
agree within the permissible variation given in Table 1, the
NOTE 3—There are no CRMs that are quicklime or hydrated lime as
determination including sample preparation shall be repeated supplied. When analyzing a quicklime or hydrated lime the CRM in
carbonate form needs to be converted to closely resemble the matrix of the
in duplicate until the results agree within the permissible
product being tested. To accomplish this conversion, heat the chosen CRM
variation. When the results agree within the permissible
for 1 h at 1000 °C, immediately prior to analysis and protect it from
variation, their average shall be accepted as the correct value.
hydration or carbonation with sealed containers and desiccation during
For the purpose of comparing results, the percentages shall be
cooling. Carbon and sulfur may be driven off during heating, rendering the
converted CRM unsuitable as a standard for carbon and sulfur determi-
calculated to one more significant figure than reported as
nations. For carbon and sulfur determinations use the appropriate CRM in
indicated in the test methods. When a blank determination is
its normal matrix.
specified, one shall be made with each individual analysis or
7.1.4 The average of the results of acceptable duplicate
with each group of two or more samples analyzed on the same
determinations for each constituent may differ from the CRM
day for a given constituent.
certificate value by no more than the value shown in Column
7.1.2 Test results from Referee methods intended for use as
3 of Table 1. When no CRM certificate value is given, a
a basis for product acceptance or rejection, or for manufactur-
generally accepted accuracy standard for that constituent has
er’s certification, can be used only after demonstration of
not been identified. In such cases, only the differences between
precise and accurate analyses by meeting the requirements of
duplicate values as specified in 7.1.3 shall apply and notifica-
7.1.3, or except when demonstrated under 7.3.2.1. Such dem-
tion of this exception shall be reported.
onstrations may be made concurrently with analysis of the
7.1.5 In questions concerning the acceptance or rejection of
limestone, quicklime, or hydrated lime product being tested.
a limestone, quicklime, or hydrated lime product, upon request
The demonstration is required only for those constituents being
data shall be made available to all parties involved demonstrat-
used as a basis for acceptance, rejection, or certification of a
ing that precise and accurate results were obtained with CRM
limestone, quicklime, or hydrated lime, but may be made for
samples by the same analyst making the acceptance determi-
any constituent of limestone, quicklime, or hydrated lime
nation.
product for which a standard exists. Such demonstrations must
be made annually.
7.2 Optional Analyses—The alternative test methods, as
7.1.3 Demonstrations shall be made by analysis of each
opposed to reference methods, provide procedures that are, in
constituent of concern in a CRM limestone, quicklime, or
some cases, shorter or more convenient to use for routine
hydrated lime (see Notes 2 and 3). Duplicate samples shall be
determination of some constituents (see Note 4). In some
run on different days. The same test methods to be used for
instances longer, more complex procedures have been retained
analysis of the limestone, quicklime, or hydrated lime being
as alternative test methods to permit comparison of results by
tested shall be used for analysis of the CRM. If the duplicate
different procedures or for use when unusual materials are
results do not agree within the permissible variation given in
being examined, or when unusual preparation for analysis is
required. Results from alternative test methods may be used as
a basis for acceptance or rejection.
A
TABLE 1 Maximum Permissible Variations in Results
NOTE 4—It is not intended that the use of reference test methods be
(Column 1) (Column 2) (Column 3)
confined to referee analysis. A reference test method may be used in
Maximum Difference of
preference to an alternative test method when so desired. A reference test
Maximum Difference the Average of
Constituent
Between Duplicates Duplicates from CRM method must be used where an alternative test method is not provided.
B
Certificate Values
7.2.1 Duplicate analyses and blank determinations are left
Al as Al O 0.20 ±0.30
2 3
Ca as CaO 0.20 ±0.30
to the discretion of the analyst when using the alternative test
Mg as MgO 0.20 ±0.30
methods. The final results should include the number of
C (lime and hydrated 0.20 ±0.30
determinations performed and whether or not they were
lime)
C (limestone) 0.60 ±0.60
corrected for blank values.
Fe as Fe O 0.10 ±0.15
2 3
Si as SiO 0.15 ±0.30 7.3 Performance Requirements for Alternative Test Meth-
Mn 0.05 ±0.10
ods:
P 0.02 ±0.05
C 7.3.1 Definition and Scope—When analytical data obtained
Sr as SrO 0.05
in accordance with this section is required, any test method
S 0.03 ±0.05
A
may be used that meets the requirements of 7.3.2. A test
For demonstrating the performance of rapid test methods the CRM closest in
overall composition to the limestone shall be used (see Table 2). In the case of
method is considered to consist of the specific procedures,
quicklime or hydrated lime, the CRM closest in overall composition, after heating
reagents, supplies, equipment, instrument, and so forth, se-
at 1000 °C for 1 h, to the product composition shall be used, except for C and S
lected and used in a consistent manner by a specific laboratory.
determinations (see Note 3).
B
Interelement corrections may be used for any standardization provided improved
7.3.1.1 If more than one instrument is used for the same
accuracy can be demonstrated.
C analysis, use of each instrument shall constitute a separate test
No CRM currently available.
method and each must be qualified separately.
´1
C25 − 19
TABLE 2 Approved CRM List
Al as % Ca as % Mg as % Fe as % Si as % Na as %
CRM % Mn % P Sr as % SrO % S Ti as % TiO K as % K O % LOI
2 2
Al O CaO MgO Fe O SiO Na O
2 3 2 3 2 2
A B
ECRM 752-1 0.120 55.400 0.150 0.045 0.700 0.008 NC 0.019 0.007 0.009 0.020 NC 43.40
IPT 35 0.240 53.800 0.700 0.140 1.980 0.009 0.003 0.040 NC 0.013 0.100 0.004 43.00
IPT 44 0.330 50.500 2.930 0.300 2.690 0.012 0.006 0.040 NC 0.019 0.120 0.002 42.90
C
IRSID 701-1 0.550 52.700 0.600 1.040 1.990 0.022 0.022 NC 0.04 0.030 NC NC NC
C
NIST 1c 1.300 50.300 0.420 0.550 6.840 0.019 0.017 0.030 NC 0.070 0.280 0.020 39.90
D
NIST 88B 0.336 30.120 21.030 0.277 1.130 0.012 0.002 0.008 NC (0.016) 0.103 0.029 (46.98)
BCS 368 0.170 30.800 20.900 0.230 0.920 0.050 NC 0.009 NC <0.01 (0.024) (<0.01) 46.70
IRSID 702-1 0.400 30.050 20.510 0.629 2.220 0.10 0.024 NC 0.027 0.022 NC NC NC
C
GBW 07214 0.017 54.950 0.670 0.071 0.380 0.007 0.0011 NC 0.020 NC NC NC 43.57
C
GBW 07215 0.500 51.560 2.670 0.292 1.170 0.014 0.0013 NC 0.196 NC NC NC 43.22
C
GBW 07216 0.027 36.550 16.590 0.226 0.092 0.022 0.0018 NC 0.014 NC NC NC 46.23
C
GBW 07217 0.295 30.600 20.730 0.376 0.960 0.048 0.0012 NC 0.174 NC NC NC 46.30
GBW 03106 0.640 50.380 2.280 0.290 4.380 0.0055 0.006 NC 0.006 0.034 0.14 0.07 41.58
GBW 03108 0.880 47.490 3.630 1.970 3.840 0.15 0.017 NC 0.036 0.14 0.23 0.024 41.52
IPT 48 0.170 31.000 21.200 0.170 0.450 0.011 0.010 0.009 NC 0.006 0.026 0.013 46.90
NIST 1d 0.526 52.85 0.301 0.319 4.08 0.0209 0.0413 0.0303 0.1028 (0.0306) 0.1358 0.0109 (41.57)
GBW 07214a 0.093 55.34 0.29 0.085 0.22 0.0039 0.0011 NC 0.043 NC 0.02 (0.007) 43.61
GBW 07215a 0.77 51.2 2.29 0.446 1.8 0.0108 0.0013 NC 0.302 NC 0.168 0.025 42.57
GBW 07216a 0.024 35.02 17.88 0.495 0.049 0.015 0.0012 NC 0.0093 NC 0.001 0.013 46.32
GBW 07217a 0.017 32.11 20.37 0.224 0.021 0.0248 0.001 NC 0.018 NC 0.0011 0.023 46.89
BCS 513 0.108 55.59 0.182 0.0275 0.228 0.0074 NC 0.0176 0.0097 NC 0.015 NC 43.61
IPT 122 1.24 32 17.5 0.65 4.3 0.0333 0.0306 0.018 NC 0.06 0.43 0.019 43.3
JLs-1 0.0207 55.09 0.606 0.0178 0.12 0.00162 0.019 0.0349 0.0123 (0.002) 0.00297 0.002 (43.82)
JDo-1 0.0174 33.96 18.47 0.0222 0.216 0.0051 0.022 0.0137 (0.0095) (0.00133) 0.00232 0.013 (47.1)
A
This CRM is still available but its named has been changed from BCS 393.
B
NC = Not Certified.
C
This CRM is no longer commercially available but use of private stock is allowed.
D
( ) = not certified; data for information only.

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C25 − 19
7.3.2 Qualification of a Test Method—Prior to use each test constituents. When indirect test methods are involved, as when
method (see 7.3.1) must be qualified for each material that will a value is obtained by difference, corrections shall be made for
be tested. Qualification data or, if applicable, requalification minor constituents in order to put the analyses on a comparable
data shall be made available. basis prior to determining the differences (see Note 6). For any
constituents affected, a test method also shall be requalified
7.3.2.1 Using the test method chosen, make single determi-
nations for each constituent under consideration on the CRM after any substantial repair or replacement of one or more
critical components of an instrument essential to the test
which in overall composition most closely resembles the
limestone, quicklime, or hydrated lime to be tested (see Note method.
2). Complete two rounds of tests on nonconsecutive days
NOTE 6—Instrumental analyses can usually detect only the element
repeating all steps of sample preparations. Calculate the
sought. Therefore, to avoid controversy, the actual procedure used for the
differences between values and the averages of values from the elemental analysis should be noted when differences with reference
procedures exist. For example, Combined Oxides of Iron and Aluminum
two rounds of tests. Blank determinations are not required, if it
by Wet Test should be compared to the sum of Fe O and Al O obtained
2 3 2 3
has been determined that blank values do not affect the validity
instrumentally.
of the data. Blank or interference-corrected data must be so
7.3.6.4 If an instrument or piece of equipment is replaced
designated.
even by one of identical make and model, or is significantly
7.3.2.2 The differences between duplicates obtained for any
modified, a previously qualified test method using such new or
single constituent shall not exceed the limits shown in Column
modified instrument or equipment shall be considered a new
2 of Table 1.
method and must be qualified in accordance with 7.3.2.
7.3.2.3 For each constituent the average of the duplicates
obtained shall be compared to the CRM Certificate value and 7.4 Precision and Bias—Different analytical test methods
shall not differ from the certified value by more than the value are subject to individual limits of precision and bias. It is the
in Column 3 of Table 1. The qualification testing shall be responsibility of the user to demonstrate that the test methods
conducted with newly prepared specimens. used at least meet the requirements shown in Table 1.
7.3.2.4 The standardization, if applicable, used for qualifi-
8. Insoluble Matter Including Silicon Dioxide (Standard
cation and analysis of each constituent shall be determined by
Method)
valid curve-fitting procedures (see Note 5). Restandardization
8.1 Scope—This test method is based on a double evapora-
shall be performed as frequently as required to ensure that the
tion to dryness of the hydrochloric acid solution of the
accuracy and precision in Table 1 are maintained.
limestone or lime sample to convert silicon dioxide (SiO ) to
NOTE 5—An actual drawing of a curve is not required, if such a curve
the insoluble form. The acid-insoluble residue of a typical
is not needed for the method in use. A point-to-point, saw-tooth curve that
limestone consists of free silica and a mixture of minerals such
is artificially made to fit a set of data points does not constitute a valid
as clay, mica, feldspar, tourmaline, barytes, garnet, zircon,
curve-fitting procedure.
rutile, and so forth.
7.3.3 Partial Results—Test methods that provide acceptable
8.2 Summary of Test Method—After dissolution in hydro-
results for some constituents, but not for others, may be used
only for those components for which acceptable results are chloric acid, the silica is dehydrated by a double evaporation to
dryness. After each dehydration, the dry salts are redissolved
obtained.
with dilute hydrochloric acid, the solution is filtered, and the
7.3.4 Report of Results—Chemical analyses obtained by
siliceous residue and other insoluble matter separated. The two
qualified alternative test methods shall be indicated as having
papers containing the residues are combined, ignited, and
been obtained by alternative methods and the type of test
weighed.
method used shall be designated.
7.3.5 Rejection of Material—See 7.1 and 7.2.
8.3 Procedure:
7.3.6 Requalification of a Test Method:
8.3.1 Weigh 0.5 g of quicklime or hydrated lime, or 1.0 g of
7.3.6.1 Requalification of a test method, as defined in 7.3.2,
limestone ground to pass a No. 50 (250-μm) sieve (see Note 7).
shall be required annually.
If the sample is a limestone or hydrated lime, ignite in a
7.3.6.2 Requalification also shall be required upon receipt of
covered platinum crucible in an electric muffle (see Note 8) at
substantial evidence that the test method may not be providing 950 °C for 15 min or longer to effect complete decomposition.
data in accordance with Table 1. Such requalification may be Transfer to an evaporating dish, preferably of platinum (see
limited to those constituents indicated to be in error and shall Note 9), containing about 10 mL of water, mix to a thin slurry,
be carried out prior to further use of the method for analysis of add 5 to 10 mL of HCl, and digest with the aid of gentle heat
those constituents. and agitation until solution is complete (see Note 10).
7.3.6.3 Substantial evidence that a test method may not be
NOTE 7—Due to the rapidity with which quicklime and hydrated lime
providing data in accordance with Table 1 shall be considered
absorb water and carbon dioxide from the air, samples must be protected
to have been received when a laboratory is informed that in tightly stoppered containers at all times. Samples for analysis are to be
weighed quickly and the sample container re-stoppered immediately after
analysis of the same material by Reference Test Methods run in
the sample has been removed.
accordance with 7.1.1, a certified value of an approved CRM,
NOTE 8—Ignition of the sample in an electric muffle is far superior to
or an accepted value of a known secondary standard differs
flame ignition. However, if an electric muffle is not available, flame
from the value obtained by the test method in question by more
ignition and the blast lamp may be used.
than twice the value of Column 2 of Table 1 for one or more NOTE 9—If a platinum dish is not available, porcelain may be used. A
´1
C25 − 19
glass container positively must not be used.
The fuming perchloric acid is refluxed at this temperature for
NOTE 10—Alternatively, the loss on ignition (LOI) can be determined
a short period of time to completely dehydrate the silica. The
first, using 0.5 g of sample. The insoluble matter including silicon dioxide
residue of silica and insoluble matter is filtered and washed free
can then be assayed using the ignited product that remains in the LOI
of acids and salts. The filter paper containing the residue is
crucible.
burned off, the resultant ash is ignited at high temperature until
8.3.2 Evaporate the solution to dryness on a steam bath.
the ash is white, and then is weighed.
When dry or nearly so, cover the dish and place it in an air bath
9.3 Procedure: Warning—Perchloric acid (HClO ) is an
or drying oven or on a metal triangle resting on a hot plate.
extremely reactive liquid. When using HClO , there are pre-
Heat for 1 h at 100 °C, remove the dish from the heat, and 4
cautions to be followed which, if unheeded, may lead to serious
allow the dish and contents to cool slightly.
explosions. Contact of the hot concentrated acid with organic
8.3.3 Drench the cooled mass with 20 mL (1 + 1) HCl and
matter must be absolutely avoided. Any organic matter in the
place on the water bath for 10 min. Filter the mixture
sample must first be destroyed by the addition of nitric acid
containing the insoluble residue through a retentive filter of
(HNO ) to the sample prior to fuming with HClO . All
3 4
suitable size. Wash filter thoroughly with warm, diluted
evaporations involving HClO must be done in a well-
(5 + 95) HCl and then twice with hot water. Reserve the paper 4
ventilated hood made of nonporous and inorganic material,
and residue.
preferably Type 316L stainless steel. Facilities should be
8.3.4 Evaporate the filtrate to dryness, dehydrate and extract
provided for washdown procedures that should be performed
the residue with HCl as before, but this time heat the acidified
regularly and thoroughly. These precautions on perchloric acid
solution for 1 to 2 min. Filter through a second and smaller
use are fully discussed in Practices E50.
piece of retentive filter paper and wash as before. Retain the
9.3.1 Weigh 0.5 g of quicklime or hydrated lime, or 1 g of
filtrate for iron, aluminum, calcium, and magnesium determi-
limestone ground to pass a No. 50 (250-μm) sieve. Transfer the
nations; combine the two wet papers containing the separated
sample to a 250-mL beaker, wet carefully with a few millilitres
residues and transfer to a weighed platinum crucible.
of water, and dissolve cautiously with 10 mL of concentrated
8.3.5 Char carefully without allowing the paper to inflame,
nitric acid. Add 20 mL of perchloric acid and boil until dense
and then ignite at 1000 °C for 30 min in an electric muffle
white fumes appear. If the solution darkens at this point, add
furnace (see Note 8). Cool in a desiccator and weigh. The
several millilitres of HNO until the solution clears. Heat again
increase in weight represents the insoluble matter including
to fumes.
SiO .
9.3.2 With the beaker covered, boil gently for 15 min to
8.4 Calculation—Calculate the percentage of insoluble mat-
completely dehydrate the silica. Never allow contents to
ter including silicon dioxide to the nearest 0.01 % as follows:
become solid or go to dryness, otherwise the separation of
Insoluble matter including SiO 5 A/B × 100 (1)
~ !
silica will be incomplete. If this happens, add more HClO and
repeat the dehydration.
where:
9.3.3 Cool, add 50 mL of water, heat to boiling, and filter
A = mass of ignited residue, g, and
immediately using medium textured paper. Wash paper and
B = original mass of sample, g.
residue thoroughly (at least 15 times) with hot water. Test with
8.5 Precision and Bias—This test method was originally
pH paper until washings are free of acid (see Note 11). Reserve
approved for publication before the inclusion of precision and
the filtrate for iron, aluminum, calcium, and magnesium
bias statements within standards was mandated. The user is
determinations.
cautioned to verify by the use of reference materials, if
NOTE 11—The filter paper and silica residue must be washed free of
available, that the precision and bias of this test method are
perchlorate salts to prevent small explosions from occurring in the
adequate for the contemplated use.
crucible when the filter paper is charred and ignited.
9.3.4 Place the filter paper and contents in a weighed
9. Insoluble Matter Including Silicon Dioxide (Optional
platinum or porcelain crucible and heat gently with a low flame
Perchloric Acid Method)
until paper chars without inflaming, or alternatively char in an
electric muffle at 300 to 400 °C. Slowly raise the temperature
9.1 Scope—In this test method the insoluble matter includ-
until the carbon has been burned and the ash is white. Finally,
ing silicon dioxide is determined gravimetrically as in the
ignite at 1000 °C for 30 min. Cool in a desiccator and weigh as
standard method except that perchloric acid is used to dehy-
insoluble matter including SiO .
drate the silica. The procedure is more rapid than in the
standard method because only a single dehydration is neces-
9.4 Calculation—Calculate the percentage of insoluble mat-
sary. Fuming perchloric acid is a very powerful dehydrating
ter including silicon dioxide to the nearest 0.01 % as follows:
agent, and silicic acid can usually be completely converted to
Insoluble matter including SiO , % 5 A/B × 100 (2)
~ !
the insoluble silicon dioxide in less than 20 min. This test
where:
method has been determined by other agencies such as the
Association of Official Agricultural Chemists (AOAC) to be
A = mass of ignited residue, g, and
comparable to the standard hydrochloric acid method.
B = original mass of sample, g.
9.2 Summary of Test Method—The sample is decomposed 9.5 Precision and Bias:
without prior ignition by a mixture of nitric (HNO ) and 9.5.1 Four laboratories cooperated in testing on four lime-
perchloric (HClO ) acids and evaporated to fumes of HClO . stone samples and three laboratories cooperated in testing on
4 4
´1
C25 − 19
an additional eight limestone samples thereby obtaining the 10.4 Precision and Bias:
precision data summarized in Table 3. 10.4.1 Three laboratories cooperated in testing on four
9.5.2 The user is cautioned to verify by the use of reference limestone samples and two laboratories cooperated in testing
materials, if available, that the bias of this test method is on an additional eight limestone samples thereby obtaining the
adequate for the contemplated use. precision data summarized in Table 3.
10.4.2 The user is cautioned to verify by the use of reference
10. Silicon Dioxide
materials, if available, that the bias of this test method is
adequate for the contemplated use.
10.1 Scope—For control purposes or routine
determinations, a separate analysis of SiO may not be neces-
11. Insoluble Matter
sary. However, for certain applications in process industries,
the amount of silica derived from the lime or limestone could
11.1 Scope—The difference between the mass of insoluble
be important. To satisfy situations such as this, silicon dioxide
matter (including silicon dioxide) and silicon dioxide repre-
may be determined by volatilizing the SiO from the insoluble
sents the mass of insoluble matter other than silicon dioxide.
residue with hydrofluoric acid and the percent SiO determined
The insoluble matter contains the remnants of any clay,
by the difference in mass obtained.
siliceous minerals, or other refractory material present in
limestone. The elemental components are mainly iron and
10.2 Procedure:
10.2.1 To the ignited residue in the platinum crucible (see aluminum which should be removed and added to the main
8.3.5 or 9.3.4), add 5 mL of water, 5 mL of hydrofluoric acid filtrate from the SiO separation. If the insoluble matter
(HF), and 1 or 2 drops of H SO . including silica is reported as such and no hydrofluoric acid
2 4
Warning—All acids should be handled with care, but extra treatment is indicated, then there is no need to make a recovery
of the metals and the insoluble residue may be discarded.
precaution is required with hydrofluoric acid. This is a very
dangerous acid, harmful to eyes and skin; rubber gloves and
11.2 Procedure—The insoluble matter left in the crucible
goggles should be worn when using this acid. It does its work
after the silica is volatilized with HF may be dissolved by
silently and leaves a festering sore that is slow to heal. Any
fusing the residue with 2 to 3 g of sodium carbonate (Na CO )
2 3
acid that touches the skin should be immediately washed off
(see Note 12). Cool the melt and dissolve it in diluted HCl. Add
with copious quantities of water. A physician should be notified
the solution to the filtrate from the dehydration and separation
immediately if any acid is sprayed into the eyes or if prolonged
of insoluble matter including silicon dioxide (see 8.3.4 or
contact with the skin occurs.
9.3.3).
10.2.2 Evaporate to dryness on a hot plate and heat in an
NOTE 12—Fusion with pyrosulfate is to be avoided because this will
electric muffle at 1000 °C (see Note 8) for 2 or 3 min. Cool in
introduce undesirable sulfates into the solution.
a desiccator and weigh. The difference between this mass and
11.3 An alternative fusion can also be made using either
the mass of insoluble matter including silicon dioxide is the
lithium metaborate or lithium tetraborate as opposed to using
mass of SiO .
sodium carbonate.
10.3 Calculation—Calculate the percent of silicon dioxide
11.4 Calculation—Calculate the percentage of insoluble
to the nearest 0.01 % as follows:
matter other than silicon dioxide to the nearest 0.01 % as
SiO , % 5 ~@A 2 B! / C# × 100 (3)
follows:
where:
A = mass of ignited residue, g (insoluble matter including
Insoluble matter other than SiO , % 5 A 2 B (4)
SiO ),
where:
B = mass of ignited residue less SiO , g, and
C = original mass of sample, g. A = insoluble matter including SiO , %, and
TABLE 3 Precision Summary of Classical Test Methods
A A
Repeatability Reproducibility
Average, Range, %
Section Test Method
% Found Found
(R , E173) (R , E173)
1 2
8 Insol + SiO (Standard) . . . . . . . . . . . .
9 Insol + SiO (Optional) 1.405 0.09–6.40 0.184 0.351
10 SiO 1.177 0.03–5.36 0.128 0.146
11 Insoluble Matter 0.242 0.02–0.93 0.169 0.204
12 Combined Oxides 0.459 0.22–1.21 0.181 0.282
13 Fe O 0.180 0.05–0.36 0.064 0.183
2 3
15 Al O 0.268 0.10–0.88 0.165 0.223
2 3
16 CaO (Gravimetric) 54.46 53.4–55.1 0.558 1.020
17 CaO (Volumetric) 30.57 30.4–30.7 0.371 1.132
17 CaO (Volumetric) 53.82 49.6–55.3 0.187 0.298
18 MgO (Gravimetric) 0.817 0.19–2.28 0.158 0.210
18 MgO (Gravimetric) 21.34 21.1–21.5 0.652 1.716
19 Loss on Ignition 43.73 43.6–43.9 0.158 0.463
A
Average and range of the limestones tested.
´1
C25 − 19
(see Note 15). Heat the solution containing the precipitate to
B = SiO , %.
boiling and boil for 50 to 60 s. Remove from heat and allow the
11.5 Precision and Bias:
precipitate to settle (not more than 5 min). Filter using
11.5.1 Three laboratories cooperated in testing on four
medium-textured paper and wash the precipitate two or three
limestone samples and two laboratories cooperated in testing
times without delay with a hot, 2 % solution of ammonium
on an additional eight limestone samples thereby obtaining the
chloride (NH Cl) (see Note 16).
precision data summarized in Table 3.
NOTE 14—The NH OH used to precipitate the hydroxides must be free
11.5.2 The user is cautioned to verify by the use of reference
of any dissolved carbon dioxide (CO ).
materials, if available, that the bias of this test method is
NOTE 15—At the neutral point, it usually takes 1 drop of NH OH
adequate for the contemplated use.
(1 + 1) to change the color of the solution from red to orange and another
drop to change the color from orange to yellow. If the color fades during
12. Combined Oxides (Iron, Aluminum, Phosphorus,
the precipitation or while heating, add more of the indicator. The boiling
Titanium, Manganese)
should not be prolonged as the precipitate may peptize and be difficult to
retain on the filter. The solution should be distinctly yellow when it is
12.1 Scope—The combined oxides describe a group of
ready to filter. If it is not, restore the yellow color with more NH OH
metals that form precipitates with ammonium hydroxide which
(1 + 1).
may then be ignited to their respective oxides. Historically, it
NOTE 16—Two drops of methyl red indicator solution should be added
has been the practice to report the combined oxides present in
to the NH Cl solution in the wash bottle followed by NH OH (1 + 1)
4 4
limestone samples as a group because it was not always easy or added dropwise until the color just changes to yellow. If the color reverts
to red at any time due to heating, it should be brought back to yellow by
desirable to determine each metal oxide separately. The group
the addition of a drop of NH OH (1 + 1).
of metal oxides consists primarily of the oxides of iron and
12.4.4 Set aside the filtrate and dissolve any precipitate
aluminum, with minor amounts of titanium d
...