ASTM E278-21

Standard Test Method for Determination of Phosphorus in Iron Ores by Phosphomolybdate Coprecipitation and Nitric Acid Titrimetry

SIGNIFICANCE AND USE
5.1 This test method is intended to be used for compliance with compositional specifications for phosphorus content. It is assumed that all who use these procedures will be trained analysts capable of performing common laboratory procedures 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. Appropriate quality control practices shall be followed, such as those described in Guide E882.
SCOPE
1.1 This test method covers the determination of phosphorus in iron ores, concentrates, and agglomerates.  
1.2 This test method covers the determination of phosphorus in the range from 0.01 % to 1.00 %.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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.  
1.5 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: 73.060.10 - Iron ores
• 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) - Standard Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
• Effective Date: 01-Dec-2016
• 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 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 E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• Refers: ASTM E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011

Overview

ASTM E278-21 - Standard Test Method for Determination of Phosphorus in Iron Ores by Phosphomolybdate Coprecipitation and Nitric Acid Titrimetry - is a widely recognized analytical standard developed by ASTM International. This test method specifies the laboratory procedure for determining phosphorus content in iron ores, concentrates, and agglomerates. The standard covers phosphorus measurement in the range of 0.01% to 1.00%, using phosphomolybdate coprecipitation followed by titrimetric analysis with nitric acid. This provides reliable data to ensure material quality and regulatory compliance in the iron and steel industries.

Key Topics

• Purpose and Scope: The method is intended for determining phosphorus levels in iron ore materials to verify conformity with compositional specifications.
• Sample Types: Applicable to iron ores, concentrates, and agglomerates.
• Phosphorus Range: Suitable for samples containing 0.01% to 1.00% phosphorus.
• Methodology:
  • Sample dissolution with hydrochloric and nitric acids.
  • Phosphomolybdate coprecipitation followed by filtration.
  • Dissolving the precipitate in sodium hydroxide solution.
  • Titration of excess sodium hydroxide with standard nitric acid using phenolphthalein as an indicator.
• Safety and Laboratory Practice: Requires skillful laboratory analysts, appropriate equipment, and strict adherence to safety, health, and waste disposal practices.
• Quality Control: Recommends following quality control guidelines, such as those in ASTM Guide E882, to ensure analytical reliability.
• Interference Management: Provisions are included for handling common interfering elements, such as vanadium, arsenic, and titanium, which may affect phosphorus determination.

Applications

The ASTM E278-21 standard is essential for organizations involved in the production, processing, and quality control of iron ore and related materials. Key applications include:

• Compliance Testing: Ensuring iron ore products meet industry phosphorus specifications for use in steel manufacturing and metallurgical processes.
• Laboratory Analysis: Standardized procedure for laboratories performing chemical analysis on iron ore samples, ensuring international comparability of results.
• Process Optimization: Monitoring phosphorus levels to optimize beneficiation, pelletizing, and sintering operations, which are sensitive to phosphorus content.
• Research and Development: Supporting mineralogical and process research by providing a validated method for precise phosphorus measurement.
• Regulatory Auditing: Fulfilling international reporting and quality assurance requirements, especially in contexts of cross-border material trade.

Related Standards

For enhanced laboratory accuracy and comprehensive analysis, the following ASTM standards are often used in conjunction with ASTM E278-21:

• ASTM D1193: Specification for Reagent Water, ensuring the use of high-purity water in chemical analysis.
• ASTM E29: Practice for Using Significant Digits in Test Data.
• ASTM E50: Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials.
• ASTM E135: Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials.
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method.
• ASTM E877: Practice for Sampling and Sample Preparation of Iron Ores and Related Materials for Determination of Chemical Composition.
• ASTM E882: Guide for Accountability and Quality Control in the Chemical Analysis Laboratory.

Adhering to ASTM E278-21 ensures accurate, reproducible results critical for the global iron and steel supply chain, supporting quality management, regulatory compliance, and trade 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.
Designation: E278 − 21
Standard Test Method for
Determination of Phosphorus in Iron Ores by
Phosphomolybdate Coprecipitation and Nitric Acid
Titrimetry
This standard is issued under the fixed designation E278; 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 E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the determination of phospho-
E877 Practice for Sampling and Sample Preparation of Iron
rus in iron ores, concentrates, and agglomerates.
Ores and Related Materials for Determination of Chemi-
1.2 This test method covers the determination of phospho-
cal Composition and Physical Properties
rus in the range from 0.01 % to 1.00 %.
E882 Guide for Accountability and Quality Control in the
1.3 The values stated in SI units are to be regarded as Chemical Analysis Laboratory
standard. No other units of measurement are included in this
standard. 3. Terminology
1.4 This standard does not purport to address all of the
3.1 Definitions—For definitions of terms used in this test
safety concerns, if any, associated with its use. It is the
method, refer to Terminology E135.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 The sample is dissolved in HCl and HNO . After the
1.5 This international standard was developed in accor-
addition of HClO , the solution is evaporated to strong fumes
dance with internationally recognized principles on standard-
to dehydrate the silica. The insoluble residue is filtered off,
ization established in the Decision on Principles for the
ignited, and treated for the recovery of any contained phos-
Development of International Standards, Guides and Recom-
phorus. Ammonium molybdate is added to precipitate phos-
mendations issued by the World Trade Organization Technical
phomolybdate. The precipitate is filtered off and washed free
Barriers to Trade (TBT) Committee.
from acid. It is then dissolved in an excess of standard sodium
hydroxide solution. The excess sodium hydroxide is titrated
2. Referenced Documents
with a standard solution of HNO using phenolphthalein as an
2 3
2.1 ASTM Standards:
indicator.
D1193 Specification for Reagent Water
E29 Practice for Using Significant Digits in Test Data to
5. Significance and Use
Determine Conformance with Specifications
5.1 This test method is intended to be used for compliance
E50 Practices for Apparatus, Reagents, and Safety Consid-
with compositional specifications for phosphorus content. It is
erations for Chemical Analysis of Metals, Ores, and
assumed that all who use these procedures will be trained
Related Materials
analysts capable of performing common laboratory procedures
E135 Terminology Relating to Analytical Chemistry for
skillfully and safely. It is expected that work will be performed
Metals, Ores, and Related Materials
in a properly equipped laboratory and that proper waste
disposal procedures will be followed. Appropriate quality
This test method is under the jurisdiction of ASTM Committee E01 on
control practices shall be followed, such as those described in
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
Guide E882.
responsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-
lurgical Materials.
Current edition approved Oct. 1, 2021. Published October 2021. Originally
6. Interferences
ɛ1
approved in 1965. Last previous edition approved in 2015 as E278 – 01(2015) .
DOI: 10.1520/E0278-21.
6.1 Vanadium and arsenic, elements commonly found in
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
iron ores, coprecipitate with the phosphorus. Provisions for
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
their removal or elimination of their interference are included
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. in this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E278 − 21
6.2 Titanium tends to form an insoluble compound with 7.11 Nitric Acid, Wash Solution (1 + 99)—Mix 10 mL of
phosphorus and thus may cause low values for phosphorus. concentrated HNO (sp gr 1.42) with 990 mL of water.
Provision for its removal is included in this test method.
7.12 Phenolphthalein Indicator Solution—Dissolve 0.2 g of
phenolphthalein in 100 mL of ethanol.
7. Reagents and Materials
7.13 Potassium Nitrate, Wash Solution (10 g⁄L)—Dissolve
7.1 Purity of Reagents—Reagent grade chemicals shall be
10 g of potassium nitrate (KNO ) in water, dilute to 1 L, and
used in all tests. Unless otherwise indicated, it is intended that
mix.
all reagents conform to the specifications of the Committee on
7.14 Potassium Permanganate Solution (25 g⁄L)—Dissolve
Analytical Reagents of the American Chemical Society where
25 g of potassium permanganate (KMnO ) in water and dilute
such specifications are available. Other grades may be used, 4
to 1 L.
provided it is first ascertained that the reagent is of sufficient
high purity to permit its use without lessening the accuracy of
7.15 Sodium Carbonate (Na CO ).
2 3
the determination.
7.16 Sodium Hydroxide, Stock Solution—Dissolve 300 g of
7.2 Purity of Water—Unless otherwise indicated, references
NaOHin1 Lofwater.Addaslightexcessofbariumhydroxide
to water shall be understood to mean reagent water conforming
(Ba(OH) ) to precipitate any carbon dioxide (CO ).Allow any
2 2
to Type I or Type II of Specification D1193. Type III or Type
precipitate to settle out. Store the solution in a polyethylene
IV may be used if they effect no measurable change in the
container.
blank or sample.
7.17 Sodium Hydroxide, Standard Solution (0.15 N)—
7.3 Ammonium Molybdate Solution (Acidic).
Transfer 20 mLof the clear, supernatant stock solution to a 1-L
7.3.1 Solution No. 1—Transfer 100 g of molybdic acid
flask. Dilute to the mark with freshly boiled and cooled water
(85 % MoO ) to a 600–mLbeaker containing 240 mLof water
3 and mix thoroughly. Standardize this solution against potas-
and mix thoroughly. Add 140 mL of NH OH while stirring
sium acid phthalate. It is convenient to adjust the normality of
vigorously. When dissolution is complete, filter through a
this standard solution to 0.148 N (1 mL = 0.0002 g P). Confirm
medium paper, add 60 mL of HNO , and cool.
the phosphorus value by analyzing a standard of a known
7.3.2 Solution No. 2—Add 400 mL of HNO to 960 mL of
3 phosphorus content, preferably an iron ore of similar compo-
water in a 2-L beaker and cool.
sition. Protect the NaOH solution from CO by means of a
7.3.3 Add Solution No. 1 to Solution No. 2 while stirring
soda-lime or soda-asbestos tube.
constantly. Add 0.1 g of ammonium phosphate, dibasic
7.18 Sulfurous Acid (H SO ).
2 3
((NH ) HPO ), and let stand at least 24 h before using. Use
4 2 4
only the clear supernatant liquid.
8. Hazards
7.4 Ammonium Nitrate (NH NO ).
4 3
8.1 For precautions to be observed in this test method, refer
7.5 Ferric Chloride Solution—Dissolve 0.3 g of pure iron
to Practices E50.
wire in 25 mL of HCl (1 + 1). Oxidize by adding HNO
dropwise to the hot solution. Cool, add 25 mLof HCl, dilute to
9. Sampling and Sample Preparation
1 L and mix.
9.1 Sampling—The gross sample shall be collected and
7.6 Ferrous Sulfate Solution—Dissolve 100 g of ferrous
prepared in accordance with Practice E877.
sulfate (FeSO ·7H O) in 1 L of H SO (5 + 95).
4 2 2 4
9.2 Sample Preparation—The laboratory sample shall be
7.7 Hydrobromic Acid (1 + 4)—Mix 20 mL of concentrated
pulverized to pass a No. 100 (150-µm) sieve.
hydrobromic acid (HBr, sp gr 1.49) with 80 mL of water.
NOTE 1—Some ores, such as specular hematites, may require finer
7.8 Hydrochloric Acid (1 + 1)—Mix equal volumes of con-
grinding to pass a No. 200 (75-µm) sieve.
centrated HCl (sp gr 1.19) and water.
9.3 Sample Weight—Weigh approximately (within
7.9 Hydrofluoric Acid (sp gr 1.15)—Concentrated HF.
6 25 mg) an amount of sample specified as follows:
7.10 Nitric Acid, Standard (0.15 N)—Transfer 10 mL of
Content of Phosphorus, % Weight of Sample, g
clear and water white concentrated HNO (sp gr 1.42) to a 1-L
0.01 to 0.10 2.0
flask, dilute to the mark, and mix. Standardize this solution
0.11 to 0.50 1.0
against the standard sodium hydroxide (NaOH) solution using
0.51 to 1.00 0.5
phenolphthalein as indicator. If desired, this solution may be
made equivalent t
...

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.
´1
Designation: E278 − 01 (Reapproved 2015) E278 − 21
Standard Test Method for
Determination of Phosphorus in Iron Ores by
Phosphomolybdate Coprecipitation and Nitric Acid
Titrimetry
This standard is issued under the fixed designation E278; 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.
ε NOTE—Editorial corrections were made in 1.2 and Table 1.
1. Scope
1.1 This test method covers the determination of phosphorus in iron ores, concentrates, and agglomerates.
1.2 This test method covers the determination of phosphorus in the range from 0.01 % to 1.00 %.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
1.5 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
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E877 Practice for Sampling and Sample Preparation of Iron Ores and Related Materials for Determination of Chemical
Composition and Physical Properties
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.
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 Nov. 15, 2015Oct. 1, 2021. Published December 2015October 2021. Originally approved in 1965. Last previous edition approved in 20102015
ɛ1
as E278 – 01 (2010)(2015) . DOI: 10.1520/E0278-01R15E01.10.1520/E0278-21.
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
E278 − 21
4. Summary of Test Method
4.1 The sample is dissolved in HCl and HNO . After the addition of HClO , the solution is evaporated to strong fumes to
3 4
dehydrate the silica. The insoluble residue is filtered off, ignited, and treated for the recovery of any contained phosphorus.
Ammonium molybdate is added to precipitate phosphomolybdate. The precipitate is filtered off and washed free from acid. It is
then dissolved in an excess of standard sodium hydroxide solution. The excess sodium hydroxide is titrated with a standard solution
of HNO using phenolphthalein as an indicator.
5. Significance and Use
5.1 This test method is intended to be used for compliance with compositional specifications for phosphorus content. It is assumed
that all who use these procedures will be trained analysts capable of performing common laboratory procedures 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. Appropriate quality control practices shall be followed, such as those described in Guide E882.
6. Interferences
6.1 Vanadium and arsenic, elements commonly found in iron ores, coprecipitate with the phosphorus. Provisions for their removal
or elimination of their interference are included in this test method.
6.2 Titanium tends to form an insoluble compound with phosphorus and thus may cause low values for phosphorus. Provision for
its removal is included 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 sufficient high purity
to permit its use without lessening the accuracy of the determination.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Type II conforming to Type I or Type II of Specification D1193. Type III or Type IV may be used if they effect no measurable
change in the blank or sample.
7.3 Ammonium Molybdate Solution (Acidic).
7.3.1 Solution No. 1—Transfer 100 g of molybdic acid (85 % MoO ) to a 600–mL beaker containing 240 mL of water and mix
thoroughly. Add 140 mL of NH OH while stirring vigorously. When dissolution is complete, filter through a medium paper, add
60 mL of HNO , and cool.
7.3.2 Solution No. 2—Add 400 mL of HNO to 960 mL of water in a 2-L beaker and cool.
7.3.3 Add Solution No. 1 to Solution No. 2 while stirring constantly. Add 0.1 g of ammonium phosphate, dibasic ((NH ) HPO ),
4 2 4
and let stand at least 24 h before using. Use only the clear supernatant liquid.
7.4 Ammonium Nitrate (NH NO )).
4 3
7.5 Ferric Chloride Solution—Dissolve 0.3 g of pure iron wire in 25 mL of HCl (1 + 1). Oxidize by adding HNO dropwise to
the hot solution. Cool, add 25 mL of HCl, dilute to 1 L and mix.
7.6 Ferrous Sulfate Solution—Dissolve 100 g of ferrous sulfate (FeSO ·7H O) in 1 L of H SO (5 + 95).
4 2 2 4
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, 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, http://www.usp.org.
E278 − 21
7.7 Hydrobromic Acid (1 + 4)—Mix 20 mL of concentrated hydrobromic acid (HBr, sp gr 1.49) with 80 mL of water.
7.8 Hydrochloric Acid (1 + 1)—Mix equal volumes of concentrated HCl (sp gr 1.19) and water.
7.9 Hydrofluoric Acid (sp gr 1.15)—Concentrated HF.
7.10 Nitric Acid, Standard (0.15 N)—Transfer 10 mL of clear and water white concentrated HNO (sp gr 1.42) to a 1-L flask,
dilute to the mark, and mix. Standardize this solution against the standard sodium hydroxide (NaOH) solution using
phenolphthalein as indicator. If desired, this solution may be made equivalent to the standard sodium hydroxide solution by dilution
with water.
7.11 Nitric Acid, Wash Solution (1 + 99)—Mix 10 mL of concentrated HNO (sp gr 1.42) with 990 mL of water.
7.12 Perchloric Acid (70 %) (HClO ).
7.12 Phenolphthalein Indicator Solution—Dissolve 0.2 g of phenolphthalein in 100 mL of ethanol.
7.13 Potassium Nitrate, Wash Solution (10 g ⁄L)—Dissolve 10 g of potassium nitrate (KNO ) in water, dilute to 1 L, and mix.
7.14 Potassium Permanganate Solution (25 g ⁄L)—Dissolve 25 g of potassium permanganate (KMnO ) in water and dilute to 1 L.
7.15 Sodium Carbonate (Na CO ).
2 3
7.16 Sodium Hydroxide, Stock Solution—Dissolve 300 g of NaOH in 1 L of water. Add a slight excess of barium hydroxide
(Ba(OH) ) to precipitate any carbon dioxide (CO ). Allow any precipitate to settle out. Store the solution in a polyethylene
2 2
container.
7.17 Sodium Hydroxide, Standard Solution (0.15 N)—Transfer 20 mL of the clear, supernatant stock solution to a 1-L flask. Dilute
to the mark with freshly boiled and cooled water and mix thoroughly. Standardize this solution against potassium acid phthalate.
It is convenient to adjust the normality of this standard solution to 0.148 N (1 mL = 0.0002 g P). Confirm the phosphorus value
by analyzing a standard of a known phosphorus content, preferably an iron ore of similar composition. Protect the NaOH solution
from CO by means of a soda-lime or soda-asbestos tube.
7.18 Sulfurous Acid (H SO ).
2 3
8. Hazards
8.1 For precautions to be observed in this test method, refer to Practices E50.
9. Sampling and Sample Preparation
9.1 Sampling—The gross sample shall be collected and prepared in accordance with Pra
...