ASTM E246-01(2005)

Standard Test Methods for Determination of Iron in Iron Ores and Related Materials by Dichromate Titration

SIGNIFICANCE AND USE
The determination of the total iron content is the primary means for establishing the commercial value of iron ores used in international trade.
These test methods are intended as referee methods for the determination of iron in iron ores. It is assumed that all who use these methods 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 must be followed, such as those described in Guide E 882.
SCOPE
1.1 These test methods cover the determination of total iron in iron ores, concentrates, and agglomerates in the concentration range 30 to 95 % iron.
1.2 The test methods in this standard are contained in the sections indicated as follows:
Test Method A-Iron by the Hydrogen Sulfide Reduction Dichromate Titration Method (30 to 75 % Fe)
Test Method B-Iron by the Stannous Chloride Reduction Dichromate Titration Method (35 to 95 % Fe)
Test Method C-Iron by the Silver Reduction Dichromate Titration Method (35 to 95 % Fe)
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 and health practices and determine the applicability of regulatory limitations prior to use. Specific hazards statements are given in Section 5 and in special "Warning" paragraphs throughout these test methods.

General Information

• Status: Historical
• Publication Date: 30-Apr-2005
• 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

• Replaces: ASTM E246-01 - Standard Test Methods for Determination of Iron in Iron Ores and Related Materials by Dichromate Titration
• Effective Date: 01-May-2005
• Replaced By: ASTM E246-10 - Standard Test Methods for Determination of Iron in Iron Ores and Related Materials by Dichromate Titrimetry
• Effective Date: 15-Jun-2010

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E246–01(Reapproved2005)
Standard Test Methods for
Determination of Iron in Iron Ores and Related Materials by
Dichromate Titration
This standard is issued under the fixed designation E246; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Chemical Analysis Laboratory
1.1 These test methods cover the determination of total iron
3. Significance and Use
in iron ores, concentrates, and agglomerates in the concentra-
3.1 The determination of the total iron content is the
tion range 30 to 95% iron.
primary means for establishing the commercial value of iron
1.2 The test methods in this standard are contained in the
ores used in international trade.
sections indicated as follows:
3.2 These test methods are intended as referee methods for
Test Method A—Iron by the Hydrogen Sulfide Reduction
thedeterminationofironinironores.Itisassumedthatallwho
Dichromate Titration Method (30 to 75% Fe)
use these methods will be trained analysts capable of perform-
Test Method B—Iron by the Stannous Chloride Reduction
ing common laboratory procedures skillfully and safely. It is
Dichromate Titration Method (35 to 95% Fe)
expected that work will be performed in a properly equipped
Test Method C—Iron by the Silver Reduction Dichromate
laboratory and that proper waste disposal procedures will be
Titration Method (35 to 95% Fe)
followed. Appropriate quality control practices must be fol-
1.3 This standard does not purport to address all of the
lowed, such as those described in Guide E882.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Apparatus, Reagents, and Instrumental Practices
priate safety and health practices and determine the applica-
4.1 Apparatus—Specialized apparatus requirements are
bility of regulatory limitations prior to use. Specific hazards
listed in the “Apparatus” Section in each test method.
statements are given in Section 5 and in special “Warning”
4.2 Reagents:
paragraphs throughout these test methods.
4.2.1 Purity of Reagents—Unless otherwise indicated, all
2. Referenced Documents reagentsusedinthesetestmethodsshallconformtothereagent
2 grade specifications of theAmerican Chemical Society. Other
2.1 ASTM Standards:
gradesmaybeusedprovideditisfirstascertainedthattheyare
D1193 Specification for Reagent Water
of sufficient purity to permit their use without adversely
E50 Practices for Apparatus, Reagents, and Safety Consid-
affecting the expected performance of the determination, as
erations for Chemical Analysis of Metals, Ores, and
indicated in the “Precision and Bias” Section. Reagent water
Related Materials
shall conform to Type II as described in Specification D1193.
E276 Test Method for Particle Size or Screen Analysis at
No. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores
5. Hazards
and Related Materials
5.1 For precautions to be observed in the use of certain
E877 Practice for Sampling and Sample Preparation of Iron
reagents and equipment in this test method refer to Practices
Ores and Related Materials for Determination of Chemical
E50.
Composition
E882 Guide for Accountability and Quality Control in the
6. Sampling and Sample Preparation
6.1 Collect and prepare the test sample in accordance with
These test methods are under the jurisdiction of ASTM Committee E01 on
Practice E877.
Analytical Chemistry for Metals, Ores, and Related Materials and are the direct
6.2 The test sample shall be pulverized to pass a No. 100
responsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-
(150-µm) sieve in accordance with Test Method E276.To
lurgical Materials.
Current edition approved May 1, 2005. Published June 2005. Originally
approved in 1964. Last previous edition approved in 2001 as E246–01. DOI:
10.1520/E0246-01R05. 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, http://www.usp.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E246–01 (2005)
facilitate decomposition some ores, such as specular hematite, twice by recrystallizing from water, drying at 110°C, pulver-
require grinding to pass a No. 200 (75-µm) sieve. izing in an agate mortar, and drying at 180°C to constant
weight. The titer of this solution shall be confirmed by means
TEST METHOD A—IRON BY THE HYDROGEN
of standard sample similar in type and composition to the test
SULFIDE REDUCTION DICHROMATE TITRATION
sample.
METHOD
11.3 Potassium Permanganate Solution (25 g/L)—Dissolve
25 g of potassium permanganate (KMnO ) in water and dilute
7. Scope
to1L.
7.1 This test method covers the determination of total iron
11.4 Sodium Diphenylamine Sulfonate Indicator Solution—
in iron ores, concentrates, and agglomerates in the concentra-
Dissolve 0.3 g of sodium diphenylamine sulfonate in 100 mL
tion range from 30 to 75%.
of water. Store in a dark-colored bottle.
11.5 Sodium Pyrosulfate (Na S O ).
2 2 7
8. Summary of Test Method
11.6 Sulfuric Acid-Hydrogen Sulfide Wash Solution—Add
8.1 The sample is dissolved in hydrochloric acid. The
20mLofconcentratedsulfuricacid(H SO ,spgr1.84)to900
2 4
insoluble residue is removed by filtration, ignited, and treated
mL water, cool, dilute to 1 L, and pass a rapid stream of H S
fortherecoveryofiron,andaddedtothemainsolution.Tothis
through it for at least 10 min.
solution containing all of the iron, sulfuric acid is added and
the solution evaporated to fumes to expel chlorides. The salts
12. Procedure
are dissolved in water, the solution heated to boiling, and the
12.1 Transfer approximately 0.50 g of the test specimen to
iron reduced by a rapid stream of hydrogen sulfide. The
a small weighing bottle previously dried at about 105°C. Dry
precipitated sulfides are filtered and washed with an acid-
the bottle and contents for1hat105to110°C (Note 1). Cap
sulfide wash solution until free of iron. The filtrate is then
the bottle and cool to room temperature in a desiccator.
boiled to expel the hydrogen sulfide, cooled, and titrated with
Momentarilyreleasethecaptoequalizethepressureandweigh
potassium dichromate solution, using sodium diphenylamine
the capped bottle and sample to the nearest 0.1 mg. Repeat the
sulfonate as the indicator.
drying and weighing until there is no further weight loss.
Transferthetestspecimentoa250-mLbeakerandreweighthe
9. Interferences
cappedbottletothenearest0.1mg.Thedifferencebetweenthe
9.1 None of the elements normally found in iron ores
two weights is the weight of the sample taken for analysis.
interfere with this test method. These include vanadium,
copper, and small amounts of molybdenum, which occasion- NOTE 1—Most ores yield their hygroscopic moisture at this tempera-
ture.Ifadryingtemperatureotherthanthatspecifiedisrequired,thisshall
ally occur in iron ores.
be determined by mutual agreement between manufacturer and purchaser.
10. Apparatus
12.2 Decomposition of the Sample—Moisten the sample
10.1 Hydrogen Sulfide Generator—Hydrogen sulfide shall
withafewmillilitresofwaterandadd25mLofHCl.Coverthe
be obtained from a cylinder of the compressed gas or from a
beaker and heat, maintaining a temperature below boiling until
Kipp generator. A consistent flow of 1 L/min shall be main-
mostofthedarkparticlesaredissolvedandnofurtherattackis
tained and the gas passed through a water trap to remove any
apparent. Add 5 mL of HNO and digest for another 15 min.
salts.
Remove from the source of heat, wash the sides and cover of
10.1.1 Warning—Hydrogen sulfide is extremely toxic. All
the beaker, and dilute to 50 mL with warm water. Filter the
procedures involving its use must be performed in an efficient
insolubleresidueonafine-texturepaper.Washtheresiduewith
fume hood. Refer to Hazards section in Practices E50.
warm HCl (1 + 50) until the yellow color of ferric chloride is
10.2 Crucibles, platinum, 25-mL capacity.
no longer observed and then with warm water six to eight
times.Collectthefiltrateandwashingsina600-mLbeakerand
11. Reagents and Materials
reserve as the main solution (Note 2). Place the paper and
11.1 Ferrous Ammonium Sulfate Solution (approximately
residue in a platinum crucible. Char the paper at a low
0.10 N)—Dissolve 40 g of ferrous ammonium sulfate
temperature, then ignite at 950°C. Allow the crucible to cool,
(FeSO ·(NH ) SO ·6H O) in sulfuric acid (1 +19). Transfer to
moistentheresiduewithH SO (1+1),addabout5mLofHF,
4 4 2 4 2 2 4
a 1-Lflask and dilute to volume with the same acid. When the
and heat gently to remove silica and H SO (Note 3). Cool the
2 4
sample solution is ready for titration, standardize the
crucible, add3gofNa S O , and heat until a clear melt is
2 2 7
FeSO ·(NH ) SO ·6H O solution against the standard potas-
obtained. Cool, place the crucible in a 250-mL beaker, add
4 4 2 4 2
siumdichromate(0.1000 N),asdescribedin12.5.Calculatethe
about 25 mLof water and 5 mLof HCl, and warm to dissolve
millilitres of standard potassium dichromate equivalent to 1
the melt. Rinse and remove the crucible.Add the solution and
mL of the FeSO ·(NH ) SO ·6H O solution.
washings to the main solution.
4 4 2 4 2
11.2 Potassium Dichromate, Standard Solution (0.1000
NOTE 2—If the residue is small in amount and perfectly white, the
N)—Transfer 4.9031 g of primary standard grade potassium
filtration, and treatment of the residue may be omitted without causing
dichromate (K Cr O ); previously ground in an agate mortar,
2 2 7
significant error.
and dried at 105 to 110°C, to a 1-L volumetric flask. Dissolve
NOTE 3—The treatment of the residue depends upon the nature of the
in water and dilute to 1 L. If preferred, this solution may be
minerals present. Many ores require only an H SO −HF treatment to
2 4
prepared from reagent grade K Cr O , by purifying the salt decompose the residue.
2 2 7
E246–01 (2005)
TABLE 1 Precision Data
Repeatability Reproducibility
Number of Iron Found
Sample
R R
I 2
Laboratories %
s s
r R
(2.8 s ) (2.8 s )
r R
Seine River Ore 9 57.52 0.125 0.35 0.126 0.35
Knob Lake Ore 9 58.45 0.097 0.27 0.136 0.38
NBS 27d (64.96 % Fe) 6 65.01 0.057 0.16 0.085 0.24
Chilean Iron Ore 9 66.11 0.102 0.29 0.172 0.48
A
Pooled standard deviations 0.101 0.137
A
Weighted by degrees of freedom, n for s and (n −1)for s where n = number of laboratories.
r R
equivalent in millilitres of K Cr O solution.
12.3 Reduction—To the combined solution add 10 mL of
2 2 7
HSO (1+1)andevaporatetocopiousfumesofSO (Note4).
4 3
13. Calculation
Cool, dilute to approximately 100 mL with water, and heat to
13.1 Calculate the percentage of iron as follows:
boiling.AdddropwiseKMnO solutionuntilthepermanganate
color persists. Dilute the solution to 250 mL and again heat to
iron,% 5[~A 2 B! 3 C/D] 3100 (1)
boiling for several minutes. Remove from the source of heat
where:
andpassarapidstreamofH Sthroughthesolutionfor15min.
A = millilitres of K Cr O required for titration of the
2 2 7
(Warning—Hydrogen sulfide is extremely toxic. All proce-
sample,
dures involving its use must be performed in an efficient fume
B = millilitres of K Cr O required for titration of the
2 2 7
hood. Refer to Hazards section in Practices E50.) Digest at
blank,
60°C for 15 min and filter through a medium-texture paper,
C = iron equivalent of the K Cr O , g/mL, and
2 2 7
collecting the filtrate in a 500-mL Erlenmeyer flask. Wash the
D = grams of sample used.
precipitated sulfides thoroughly with the H SO −H S wash
2 4 2
solution. Add 10 mL of H SO (1 + 1) to the solution in the
2 4 14. Precision and Bias
flask and add glass beads to prevent bumping. Boil for 10 min
14.1 Precision—Fromsixtoninelaboratoriesanalyzedfour
to expel H S (lead acetate test paper) and continue boiling for
ironoresamplestodetermineiron.Thereplicationmadebythe
anadditional10min(Note5).Removefromthesourceofheat,
different laboratories ranged from 2 to 4, averaging 3 repli-
cover the flask with a small watch glass, and cool in running
cates. The data was studied by the interlaboratory test proce-
water to 20°C.
dure of Practice E691-87 modified by weighting certain sums
NOTE 4—If the sample contains much calcium, prolonged fuming with to accommodate the unequal replication. Table 1 shows a
H SO may lead to the formation of salts that are difficult to dissolve.
summaryoftheseresults.Frompooledstandarddeviations,the
2 4
Therefore,inthepresenceofconsiderablecalcium,fumejustlongenough
overall between-laboratory reproducibility coefficient, R, was
toexpelthechloridesandnitrates.Cool,washthesidesofthebeakerwith
calculated as being 0.38.
water, and again evaporate to light fumes.
14.2 TheagreementofthedeterminationofironintheNBS
NOTE 5—If the sample contains an appreciable amount of molybde-
Standard Reference Material with the certified value shows no
num, further precipitation may occur in the filtrate when boiling out the
evidence of bias, well within a 95% confidence level
H S. The effect of residual molybdenum is not significant and may be
neglected. (R = 0.24).
12.4 Titration—Add to the cooled solution 5 mL of H PO
3 4
TEST METHOD B—IRON BY THE STANNOUS
and 5 drops of the sodium diphenylamine sulfonate indicator
CHLORIDE REDUCTION DICHROMATE
solution. Dilute to 350 mL and titrate with the standard
TITRATION METHOD
K Cr O solution to a distinct purple end point.
2 2 7
12.5 Determination of Blank—Determinetheblankvalueof 15. Scope
thereagentsconcurrentlywiththetestdetermination,usingthe
15.1 This test method covers the determination of total iron
same amount of all reagents and following all the steps of the
in iron ores, concentrates, and agglomerates in the concentra-
procedure. Immediately before titrating with the K Cr O
2 2 7
tion range from 35 to 95%.
solution add 1.0 mL, accurately measured, of the
16. Summary of Test Method
FeSO ·(NH ) SO ·6H O solution. In another beaker place 350
4 4 2 4 2
mL of cold H SO (1 + 9) and add an accurately measured 1
16.1 This test method provides two alternative dissolution
2 4
mL of the FeSO ·(NH ) SO ·6H O solution. Add 5 mL of
procedures.
4 4 2
...