ASTM E463-21

Standard Test Method for Determination of Silica in Fluorspar by Silico-Molybdate Visible Spectrophotometry

SIGNIFICANCE AND USE
5.1 This test method is intended as a referee method for compliance with compositional specifications for impurity content. It is assumed that all who use this procedure will be trained analysts capable of performing common laboratory practices skillfully and safely. It is expected that work will be performed in a properly equipped laboratory and that proper waste disposal procedures will be followed. Follow appropriate quality control practices such as those described in Guide E882.
SCOPE
1.1 This test method covers the determination of silica in fluorspar from 0.5 % to 10 % by mass.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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.  
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

• Status: Published
• Publication Date: 30-Sep-2021
• ICS: 73.060.40 - Aluminium ores
• ICS: 73.080 - Non-metalliferous minerals
• Technical Committee: E01 - Analytical Chemistry for Metals, Ores, and Related Materials
• Drafting Committee: E01.02 - Ores, Concentrates, and Related Metallurgical Materials

Relations

• Refers: ASTM E135-20 - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 01-Jan-2020
• Refers: ASTM E135-19 - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 15-May-2019
• Refers: ASTM E50-17 - Standard Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
• Effective Date: 01-Sep-2017
• Refers: ASTM E882-10(2016)e1 - Standard Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
• Effective Date: 01-Dec-2016
• Refers: ASTM E882-10(2016) - Standard Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
• Effective Date: 01-Dec-2016
• Refers: ASTM E50-11(2016) - Standard Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
• Effective Date: 01-Aug-2016
• Refers: ASTM E135-16 - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 15-May-2016
• Refers: ASTM E135-15a - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 01-Jul-2015
• Refers: ASTM E135-15 - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 15-May-2015
• Refers: ASTM E135-14b - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 15-Aug-2014
• Refers: ASTM E135-14a - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 01-Apr-2014
• Refers: ASTM E135-14 - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 15-Feb-2014
• Refers: ASTM E135-13a - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 01-Dec-2013
• Refers: ASTM E50-11 - Standard Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
• Effective Date: 15-Oct-2011
• Refers: ASTM E135-11b - Standard Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
• Effective Date: 15-Sep-2011

Overview

ASTM E463-21 is the standard test method developed by ASTM International for the determination of silica in fluorspar using silico-molybdate visible spectrophotometry. This method is a critical referee procedure, intended for the accurate quantification of silica impurities in fluorspar within the range of 0.5% to 10% by mass. The standard ensures that laboratories can reliably assess compliance with compositional specifications for impurity content, supporting quality assurance in the production and processing of fluorspar and related materials.

Key Topics

• Analytical Scope: The standard applies to the analysis of silica concentrations in fluorspar samples ranging from 0.5% to 10% by mass, utilizing SI units for measurement.
• Procedural Summary:
  • Samples are fused using anhydrous sodium borate and the melt is dissolved in dilute hydrochloric acid.
  • Silica is determined spectrophotometrically after extraction of the silico-molybdate complex with butyl alcohol at a wavelength of approximately 400 nm.
• Sample Preparation: Pulverization to pass a 150-μm sieve and drying at 105 – 110°C prior to analysis.
• Quality Control: Emphasizes the need for proper laboratory practices and adherence to quality control guidelines, such as those detailed in ASTM E882.
• Safety and Environmental Responsibility: Advises users to implement proper safety, health, and waste disposal practices in compliance with established laboratory standards and regulatory requirements.
• Precision: Interlaboratory studies have confirmed the precision of the method for various grades of fluorspar.
• Interferences: The test method is robust and not significantly affected by elements typically present in commercial fluorspars.

Applications

This standard is primarily used in industries engaged in the mining, processing, and quality control of fluorspar (calcium fluoride), a material widely employed in metallurgical, ceramic, and chemical industries. Key applications include:

• Referee Analysis: Used as an official method to verify compliance with silica impurity limits in fluorspar shipments and stockpiles.
• Quality Control: Supports manufacturers in achieving required product specifications for purity, which is essential for industrial end users.
• Environmental Compliance: Ensures that impurity levels do not exceed environmental or safety regulations where applicable.
• Material Certification: Often used for certification and qualification of fluorspar supplies for commercial or industrial use, providing reliable and standardized data.

Related Standards

• ASTM D1193: Specification for Reagent Water - Ensures consistency in water quality for spectrophotometric analysis.
• ASTM E29: Practice for Using Significant Digits in Test Data - Governs the rounding and reporting of analytical results.
• ASTM E50: Practices for Apparatus, Reagents, and Safety Considerations - Covers general laboratory procedures and safety.
• ASTM E135: Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials - Defines terms and concepts used in analytical procedures.
• ASTM E276: Test Method for Particle Size or Screen Analysis - Relevant for preparing fluorspar samples.
• ASTM E882: Guide for Accountability and Quality Control in the Chemical Analysis Laboratory - Details best practices for laboratory quality assurance.

By providing a robust, precise method for the determination of silica in fluorspar, ASTM E463-21 supports industries in maintaining high standards of product quality, regulatory compliance, and environmental responsibility. For laboratories tasked with the chemical analysis of mineral materials, this standard is an essential reference for accurate and consistent results.

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.
Designation: E463 − 21
Standard Test Method for
Determination of Silica in Fluorspar by Silico-Molybdate
Visible Spectrophotometry
This standard is issued under the fixed designation E463; 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.
1. Scope E882 Guide for Accountability and Quality Control in the
Chemical Analysis Laboratory
1.1 This test method covers the determination of silica in
fluorspar from 0.5 % to 10 % by mass.
3. Terminology
1.2 The values stated in SI units are to be regarded as
3.1 Definitions—For definitions of terms used in this test
standard. No other units of measurement are included in this
method, refer to Terminology E135.
standard.
1.3 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
4.1 The sample is fused with anhydrous sodium borate and
responsibility of the user of this standard to establish appro-
the melt is dissolved in dilute HCl. Silica is determined
priate safety, health, and environmental practices and deter-
spectrophotometrically after extraction of the silico-molybdate
mine the applicability of regulatory limitations prior to use.
complex with butyl alcohol. Spectrophotometric measurement
1.4 This international standard was developed in accor-
of the extract is made at 400 nm.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
5. Significance and Use
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical 5.1 This test method is intended as a referee method for
Barriers to Trade (TBT) Committee. compliance with compositional specifications for impurity
content. It is assumed that all who use this procedure will be
2. Referenced Documents
trained analysts capable of performing common laboratory
practices skillfully and safely. It is expected that work will be
2.1 ASTM Standards:
performed in a properly equipped laboratory and that proper
D1193 Specification for Reagent Water
wastedisposalprocedureswillbefollowed.Followappropriate
E29 Practice for Using Significant Digits in Test Data to
quality control practices such as those described in Guide
Determine Conformance with Specifications
E882.
E50 Practices for Apparatus, Reagents, and Safety Consid-
erations for Chemical Analysis of Metals, Ores, and
6. Interferences
Related Materials
E135 Terminology Relating to Analytical Chemistry for
6.1 The elements ordinarily present in commercial fluor-
Metals, Ores, and Related Materials
spars do not interfere in this test method.
E276 TestMethodforParticleSizeorScreenAnalysisatNo.
4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores and
7. Reagents and Materials
Related Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise indicated, it is intended that
all reagents conform to the specifications of the Committee on
This test method is under the jurisdiction of ASTM Committee E01 on
Analytical Reagents of the American Chemical Society where
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
responsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal- such specifications are available. Other grades may be used,
lurgical Materials.
Current edition approved Oct. 1, 2021. Published October 2021. Originally
approved in 1972. Last previous edition approved in 2014 as E463 – 14a. DOI:
10.1520/E0463-21. Reagent Chemicals, American Chemical Society Specifications, American
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Chemical Society, Washington, DC, www.chemistry.org. For suggestions on the
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM testing of reagents not listed by the American Chemical Society, see the United
Standards volume information, refer to the standard’s Document Summary page on States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention,
the ASTM website. Inc. (USPC), Rockville, MD, www.usp.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E463 − 21
provided it is first ascertained that the reagent is of sufficiently flux settles on the crucible cover. Hold the crucible while
high purity to permit its use without lessening the accuracy of cooling to avoid contamination problems. This prevents dam-
the determination. age to the beaker. Transfer the cooled crucible to the beaker.
Cover the beaker with a polyethylene sheet and secure it to the
7.2 Unless otherwise indicated, references to water shall
beaker with a rubber band.
mean reagent water conforming to Type I or II of Specification
D1193.Type III or IVmay be used if they effect no measurable 10.8 Placethebeakeronasteambathandswirloccasionally
change in the blank or sample.
until the melt is completely dissolved (Note 2). Cool, remove
and rinse the platinum crucible and cover, and add the
7.3 Ammonium Molybdate Solution (100 g⁄L)—Dissolve
washings to the beaker. Transfer the solution to a 250-mL
100 g of ammonium-heptamolybdate [(NH ) Mo O ·4H O]
4 6 7 24 2
volumetric flask. Rinse the beaker and add the rinsings to the
in 500 mL of water, dilute to 1 L, and mix.
flask. Dilute to volume, mix, and examine the solution for any
7.4 Silica (SiO )—Heat pure silicic acid in a platinum
insoluble material; if any insoluble material is noted, a new
crucible to expel combined water by gradually increasing
sample must be prepared. Transfer the solution to a dry
temperature to 1050 °C. Maintain at 1050 °C for at least 5 min.
polyethylene bottle.
Cool to room temperature in a desiccator.
NOTE 2—Complete dissolution of the melt requires about 2 h. If
7.5 Sodium Borate (Na B O )—Anhydrous powder, low-
2 4 7
dissolution is incomplete, a new sample must be prepared.
silica content.
10.9 Transfer 50-mL aliquots of the blank and sample
7.5.1 Iflowsilicasodiumborateisnotavailable,preparethe
solutions to 200-mL polyethylene or TFE-fluorocarbon bea-
reagent as follows: Transfer 247 g of boric acid to a large
kers.
platinum dish. Expel water by gradually increasing the tem-
perature to about 1000 °C. When effervescence ceases, gradu-
10.10 Transfer (10.0, 20.0, 30.0, 40.0, and 50.0)-mL ali-
ally introduce 106 g of sodium
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E463 − 14a E463 − 21
Standard Test Method for
Determination of Silica in Fluorspar by Silico-Molybdate
Visible Spectrophotometry
This standard is issued under the fixed designation E463; 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.
1. Scope
1.1 This test method covers the determination of silica in fluorspar in concentrations from 0.5 % to 10 %.10 % by mass.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
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.
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E50 Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
E135 Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials
E276 Test Method for Particle Size or Screen Analysis at No. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores and Related
Materials
E882 Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology E135.
4. Summary of Test Method
4.1 The sample is fused with anhydrous sodium borate and the melt is dissolved in dilute HCl. Silica is determined
This test method is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials and is the direct responsibility of
Subcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials.
Current edition approved Oct. 1, 2014Oct. 1, 2021. Published November 2014October 2021. Originally approved in 1972. Last previous edition approved in 2014 as
E463 – 14.E463 – 14a. DOI: 10.1520/E0463-14A.10.1520/E0463-21.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E463 − 21
photometricallyspectrophotometrically after extraction of the silico-molybdate complex with normal butyl alcohol. Photometric-
Spectrophotometric measurement of the extract is made at 400 nm.
5. Significance and Use
5.1 This test method is intended as a referee method for compliance with compositional specifications for impurity content. It is
assumed that all who use this procedure will be trained analysts capable of performing common laboratory practices skillfully and
safely. It is expected that work will be performed in a properly equipped laboratory and that proper waste disposal procedures will
be followed. Follow appropriate quality control practices such as those described in Guide E882.
6. Interferences
6.1 The elements ordinarily present in commercial fluorspars do not interfere in this test method.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
7.2 Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to Type I or II of
Specification D1193. Type III or IV may be used if they effect no measurable change in the blank or sample.
7.3 Ammonium Molybdate Solution (100 g ⁄L)—Dissolve 100 g of ammonium-heptamolybdate [(NH ) Mo O ·4H O] in 500 mL
4 6 7 24 2
of water, dilute to 1 L, and mix.
7.4 Silica (SiO )—Heat pure silicic acid in a platinum crucible to expel combined water by gradually increasing temperature to
1050 °C. Maintain at 1050 °C for at least 5 min. Cool to room temperature in a desiccator.
7.5 Sodium Borate (Na B O )—Anhydrous powder, low-silica content.
2 4 7
NOTE 1—If low silica sodium borate is not available, prepare the reagent as follows: Transfer 247 g of boric acid to a large platinum dish. Expel water
by gradually increasing the temperature to about 1000 °C. When effervescence ceases, gradually introduce 106 g of sodium carbonate into the molten
mass. Maintain at a temperature of about 1000 °C until a clear melt is obtained.
7.5.1 If low silica sodium borate is not available, prepare the reagent as follows: Transfer 247 g of boric acid to a large platinum
dish. Expel water by gradually increasing the temperature to about 1000 °C. When effervescence ceases, gradually introduce 106 g
of sodium carbonate into the molten mass. Maintain at a temperature of about 1000 °C until a clear melt is obtained. Cool and break
into pieces or grind for use.
7.6 Butyl Alcohol.
7.7 Ethyl Alcohol.
8. Hazards
8.1 For precautions to be observed in this method, refer to Practices E50.
9. Sample Preparation
9.1 The analytical sample shall be pulverized, if necessary, to pass a 150-μm sieve (see Test Method E276). Dry at 105 °C to
110 °C for a minimum of 1 h.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. DC, www.chemistry.org. For suggestions on the testing
of reagents not listed by the American Chemical Society, see the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC),
Rockville, MD.MD, www.usp.org.
E463 − 21
10. Procedure
10.1 Transfer 7 g of Na B O to each of six 25-mL platinum crucibles. Form a cavity in the center of the flux.
2 4 7
10.2 Into Crucibles 1 and 2, weigh 0.100 g to 1 g of the dry sample. Choose sample weightsmasses to provide from 5 mg to 10 mg
of SiO .
10.3 Into Crucibles 3 and 4, weigh 10.0 mg of SiO reagent.
10.4 Crucibles 5 and 6 serve as blanks.
10.5 Mix the contents of the crucibles with a platinum or polyethylene rod. Transfer adhering particles to the crucible.
10.6 Cover the crucible and heat gently until moisture is expelled. Increase the temperature until complete fusion results.
NOTE 1—A Meker burner or a muffle furnace maintained at 1000
...