ASTM E945-96
(Test Method)Standard Test Method for Determination of Zinc in Zinc Ores and Concentrates by Complexometric Tritrimetry
Standard Test Method for Determination of Zinc in Zinc Ores and Concentrates by Complexometric Tritrimetry
SCOPE
1.1 This test method covers the determination of zinc in ores, concentrates, and related materials having chemical composition within the following limits: Element Concentration Range, %Zinc 5.0 to 70.0Lead 0.5 to 50.0Copper 0.1 to 3.0Iron 0.5 to 16.0Sulfur 4.0 to 30.0Calcium 0.1 to 20.0Magnesium0.1 to 10.0Cadmium 0.1 to 8.0Arsenic 0.01 to 1.0Antimony0.01 to 0.005Bismuth 0.001 to 0.1Cobalt 0.1 to 0.5Nickel 0.3 to 3.0Silver 0.00 to 150 oz/tonGold 0.00 to 1.0 oz/ton
1.2 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.
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Designation: E 945 – 96
Standard Test Method for
Determination of Zinc in Zinc Ores and Concentrates by
Complexometric Titration
This standard is issued under the fixed designation E 945; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 882 Guide for Accountability and Quality Control in the
Chemical Analysis Laboratory
1.1 This test method covers the determination of zinc in
E 1024 Guide for Chemical Analysis of Metals and Metal
ores, concentrates, and related materials having chemical
Bearing Ores by Flame Atomic Absorption Spectropho-
composition within the following limits:
tometry
Element Concentration Range, %
3. Summary of Test Method
Zinc 5.0 to 70.0
Lead 0.5 to 50.0
3.1 The sample, after appropriate acid decomposition,
Copper 0.1 to 3.0
evaporated to near dryness. The salts are dissolved in acid,
Iron 0.5 to 16.0
Sulfur 4.0 to 30.0
interfering elements are removed, and the zinc is extracted a
Calcium 0.1 to 20.0
thiocyanate complex into MIBK. Zinc is determined in the
Magnesium 0.1 to 10.0
extract by titrating with EDTA, using an internal indicator.
Cadmium 0.1 to 8.0
Arsenic 0.01 to 1.0
Antimony 0.01 to 0.005
4. Significance and Use
Bismuth 0.001 to 0.1
4.1 This test method is primarily intended to test materials
Cobalt 0.1 to 0.5
Nickel 0.3 to 3.0
for compliance with compositional specifications. It is assumed
Silver 0.00 to 150 oz/ton
that all who use this test method will be trained analysts
Gold 0.00 to 1.0 oz/ton
working in properly equipped laboratories.
1.2 This standard does not purport to address all of the
4.2 Appropriate quality control practices shall be followed
safety concerns, if any, associated with its use. It is the
such as those described in Guide E 882.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 5. Interferences
bility of regulatory limitations prior to use.
5.1 With the exception of cadmium and cobalt, elements do
not interfere if their concentrations are under the maximum
2. Referenced Documents
limits shown in 1.1.
2.1 ASTM Standards:
5.2 When the cadmium content is above 5.0 % in the
D 1193 Specification for Reagent Water
material to be analyzed, some of the cadmium is extracted and
E 29 Practice for Using Significant Digits in Test Data to
will titrate as zinc. The addition of potassium iodide before the
Determine Conformance with Specifications
titration serves to prevent the interference of cadmium. The
E 50 Practices for Apparatus, Reagents, and Safety Precau-
amount of potassium iodide solution to add in order to prevent
tions for Chemical Analysis of Metals
the interference of cadmium is listed in 12.10.3.
E 173 Practice for Conducting Interlaboratory Studies of
5.3 Cobalt is extracted and titrated with the zinc. If the
Methods for Chemical Analysis of Metals
cobalt content of the material to be analyzed is less than
E 663 Practice for Flame Atomic Absorption Analysis
0.05 %, the interference is negligible. For cobalt contents
greater than 0.05 %, the cobalt must be extracted as outlined in
12.9.5.
This test method is under the jurisdiction of ASTM Committee E-1 on
Analytical Chemistry for Metals, Ores, and Related Materials and is the direct
responsibility of Subcommittee E01.02 on Ores, Concentrates, Refractories, Ce-
6. Apparatus
ment, and Related Metallurgical Materials.
6.1 Atomic absorption spectrophotometers shall conform to
Current edition approved April 10, 1996. Published June 1996. Originally
published as E 945 – 83. Last previous edition E 945 – 95. Practice E 663 or Guide E 1024.
Annual Book of ASTM Standards, Vol 11.01.
6.2 Magnetic Stirrer, with TFE-fluorocarbon covered mag-
Annual Book of ASTM Standards, Vol 14.02.
netic stirring bar. A magnetic stirrer provided with illumination
Annual Book of ASTM Standards, Vol 03.05.
is preferred.
Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 945
7. Reagents ethanol is recommended for this reason.
7.10 Ferric Chloride Solution (140 g/L)—Dissolve 14 g of
7.1 Purity of Reagents—Reagent grade chemicals shall be
ferric chloride (FeCl ·6H O) in water and dilute to 100 mL.
used in all tests. Unless otherwise indicated, it is intended that 3 2
7.11 4-Methyl-2-Pentanone (MIBK)—CH COCH CH
3 2
all reagents conform to the specifications of the Committee on
(CH ) .
Analytical Reagents of the American Chemical Society where 3 2
7.12 2-Nitroso-1-Naphthol Solution (10 g/L)—Dissolve 0.5
such specifications are available. Other grades may be used,
g of 2-nitroso-1-naphthol (NOC H OH) in 50 mL of acetic
provided it is first ascertained that the reagent is of sufficient 10 6
acid. Prepare fresh as needed.
high purity to permit its use without lessening the accuracy of
7.13 Potassium Iodide (1000 g/L)—Dissolve 100 g of
the determination.
potassium iodide (KI) in distilled water and dilute to 100 mL.
7.2 Purity of Water—Unless otherwise indicated, references
7.14 Sodium Fluoride Solution (20 g/L)—Dissolve 10 g of
to water shall be understood to mean reagent water as defined
sodium fluoride (NaF) in water and dilute to 500 mL. Store in
by Type I of Specification D 1193.
a polyethylene bottle.
7.3 Ammonium Fluoride Solution (250 g/L)—Dissolve 250
7.15 Thiourea Solution (100 g/L)—Dissolve 50 g of thio-
g of ammonium fluoride (NH F) in water and dilute to 1 L.
urea (NH CSNH ) in water and dilute to 500 mL.
2 2
Store in a polyethylene bottle.
7.16 Xylenol Orange Tetrasodium Salt Indicator Solution (2
7.4 Ammonium Chloride Solution (250 g/L)—Dissolve 250
g/L)—Dissolve 100 mg of xylenol orange tetrasodium salt in
g of ammonium chloride (NH Cl) in water and dilute to 1 L.
water and dilute to 50 mL.
7.5 Ammonium Thiocyanate (500 g/L)—Dissolve 500 g of
7.17 Zinc, Standard Solution (1 mL–3.50 mg)—Dissolve
ammonium thiocyanate (NH SCN) in distilled water and dilute
3.50 g of zinc (minimum purity 99.99 %) in 10 mL of HNO
to1L. 3
and 25 mL of water. Heat gently; when dissolution is complete,
7.6 Buffer Solution (pH 5.5)—Dissolve 250 g of hexameth-
boil. Cool. Transfer to a 1-L flask. Dilute to the mark and mix
ylenetetramine (C H N ) in 750 mL of water. Add 57 mL of
6 12 4
thoroughly.
acetic acid, dilute to 1 L, and mix.
7.7 Chloroform (CHCl ).
3 8. Hazards
7.8 Disodium Ethylenedinitrilo Tetraacetate Dihydrate
8.1 For precautions to be observed in the use of certain
(EDTA) Standard Solution—Prepare a solution as directed for
reagents in this test method, refer to Practices E 50.
Reagent No. 22, use the following table as a guide for the
specific weight of salt to use.
9. Sampling and Sample Preparation
9.1 The gross sample shall be collected and prepared so as
NOTE 1—The use of varying concentrations of EDTA solution allows
the volume of the titrant to be between 30 and 50 mL. to be representative of the material to be analyzed.
9.2 Pulverize the laboratory sample to pass a No. 100
Amount of
EDTA Standard Zinc
(150-μm) sieve.
If the expected zinc is: Concentration Solution to Use
5 to 20 % 6 g/L 10 mL
10. Rounding Calculated Values
20 to 40 % 12 g/L 30 mL
10.1 Calculated values shall be rounded to the desired
40 to 56 % 16 g/L 40 mL
56 to 70 % 20 g/L 50 mL
number of places as directed in the Rounding-Off Procedure
7.8.1 Standardize the EDTA solution by pipetting the sug- section of Practice E 29.
gested amount of standard zinc solution into a 250-mL sepa-
11. Interlaboratory Studies
ratory funnel. Add 10 drops of ferric chloride solution, add
11.1 This test method has been evaluated in accordance with
distilled water to adjust volume to 50 mL, mix, and proceed as
Practice E 173.
directed in 12.9.2. It is recommended that replicate standard-
izations be made to ensure better accuracy.
12. Procedure
7.8.2 Calculate the zinc equivalent of the EDTA solution as
12.1 Weigh approximately 2.5 g of sample into a weighing
follows:
bottle. Dry the bottle and contents at least1hat 105°C,
...
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