ASTM E1805-21

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: E1805 − 13 E1805 − 21
Standard Test Method for
Determination of Gold in Copper Concentrates by Fire
Assay Gravimetry
This standard is issued under the fixed designation E1805; 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 is for the determination of gold in copper concentrates in the content range from 0.2 μg/g to 17 17 μg μg/g.⁄g.
NOTE 1—The lower scope limit is set in accordance with Practice E1601.
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. For specific warning statements, see 11.3.1, 11.5.4, and 11.6.5.
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
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E882 Guide for Accountability and Quality Control in the Chemical Analysis Laboratory
E1601 Practice for Conducting an Interlaboratory Study to Evaluate the Performance of an Analytical Method
3. Terminology
3.1 For definitions of terms used in this test method, refer to Terminology E135.
4. Summary of Test Method
4.1 A test sample of copper concentrate is fluxed and fused in a clay crucible. The precious metals are reduced, collected in a lead
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 April 1, 2013Oct. 1, 2021. Published June 2013October 2021. Originally approved in 1996. Last previous edition approved in 20072013 as
E1805 - 07.E1805 – 13. DOI: 10.1520/E1805-13.10.1520/E1805-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. 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
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button, and then cupelled to remove the lead. The remaining doré bead is parted with nitric acid to remove the silver and other
impurities from the gold. The gold is then annealed, cleaned, and weighed on a microbalance.
5. Significance and Use
5.1 In the metallurgical process used in the mining industries, gold is often carried along with copper during the flotation
concentration process. Metallurgical accounting, process control, and concentrate evaluation procedures for this type of material
depend on an accurate, precise measurement of the gold in the copper concentrate. This test method is intended to be a reference
method for metallurgical laboratories and a referee method to settle disputes in commercial transactions. It is also a definitive
method intended to test materials for compliance with compliance with compositional specifications and to provide data for
certification of reference materials. It is essential that each performance of the method be validated by applying it to appropriate
reference materials at the same time and in the same manner as it is applied to the unknowns.
5.2 It is assumed that all who use this test method will be trained analysts capable of performing skillfully and safely. It is expected
that the work will be performed in a properly equipped laboratory under appropriate quality control practices such as those
described in Guide E882.
6. Interferences
6.1 Elements normally found in copper concentrates within the limits of 1.1 do not interfere. High concentrations of arsenic,
antimony, tellurium, bismuth, nickel, and platinum group metals (and, in some instances, copper), however, may interfere with the
fusion and cupellation steps.
7. Apparatus
7.1 Analytical Balance, capable of weighing to 0.1 g.
7.2 Assay Mold, 100-mL100 mL capacity.
7.3 Cube or Cone Mixer, 1000-g1000 g capacity.
7.4 Cupel, magnesite or bone ash, 40-g40 g lead capacity.
7.5 Drying Oven, forced air circulation with temperature control, 104 °C.
7.6 Fire Assay Bead Brush.
7.7 Fire Assay Bead Pliers.
7.8 Fire Assay Clay Crucible, 20-g20 g to 30-g30 g sample capacity.
7.9 Fire Assay Muffle Furnace, gas-fired or electric, equipped with air circulation systems and with draft controls, capable of
temperatures to 1100 °C 6 10 °C, and with ventilation controls for acid and lead fumes.
7.10 Fire Assay Tongs, crucible and cupel.
7.11 Fire Assay Tumble Mixer—an industrial mixer-crucible tumbler.
7.12 Hot Plate, with variable temperature control and ventilation controls for acid fumes.
7.13 Jaw Crusher, capable of reducing cupels and slag to pass a 4-mm4 mm sieve.
7.14 Ring Pulverizer, capable of 250-g250 g minimal capacity.
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7.15 Semi-Microbalance, capable of weighing to 0.001 mg.
7.16 Steel Hammer.
8. Reagents and Materials
8.1 Borax Glass (Na B O ).
2 4 7
8.2 Cupel Correction Flux—Blend the following ingredients in the listed proportions:
Borax Glass 15 g
Flour 2 g
Lead Oxide 30 g
Potassium Carbonate 45 g
Silica 12 g
8.3 Fire Assay Flux Mixture—Blend the following ingredients in the listed proportions:
Borax Glass 15 g
Lead Oxide 55 g
Potassium Carbonate 6 g
Potassium Nitrate 13 g
Silica 6 g
Sodium Carbonate 20 g
NOTE 2—Perform a preliminary fusion to determine lead button weight. If a 30-g30 g to 40-g40 g lead button is not obtained, adjust the amount of KNO
and try again. Increasing the KNO produces a smaller lead button, and decreasing the KNO produces a larger one.
3 3
8.4 Flour, ground wheat.
8.5 Lead Oxide, Litharge, (PbO)—Containing less than 0.02 μg/g gold and less than 0.40 μg/g silver.
8.6 Potassium Carbonate, Potash (K CO ).
2 3
8.7 Potassium Nitrate, Niter (KNO ).
8.8 Silica (SiO ), 95 % minimum purity, particle size less than 180 μm.
8.9 Silver Foil, 99.9 % purity with less than 0.10 μg/g gold content.
8.10 Silver Solution (1 g/L)—Add 1.557 g silver nitrate to 1000 mL of water containing 5 mL of HNO , mix. Store in a dark bottle.
8.11 Sodium Carbonate, Soda Ash (Na CO ), anhydrous technical grade.
2 3
8.12 Sodium Chloride, salt (NaCl).
8.13 Purity of Reagents—Use reagent grade chemicals in all tests. Unless otherwise indicated, 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 reagents are of sufficiently high purity to permit their use without
lessening the accuracy of the determination.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Reagent Chemicals and Standards, by Joseph Rosin, D. Nostrand Co., Inc., New York, NY, and the United States Pharmacopeia and
National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
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8.14 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
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.
9. Hazards
9.1 For precautions to be observed in the use of certain reagents in this test method, refer to Practice E50.
9.2 See specific warnings in 11.3.1, 11.5.4, 11.6.5.
10. Sampling and Sample Preparation
10.1 Collect, store, and handle gross samples in accordance with the safety and materials guidelines in Practice E50. Gross
samples must be free of all extraneous materials.
10.2 Dry the laboratory sample to constant weight at 104 °C.
NOTE 3—If the gross sample was dried at a low temperature (e.g. (for example, 60 °C for mercury) take the low temperature portion(s) and a separate
moisture sample, prior to drying at 104 °C.
10.3 Grind the laboratory sample in a ring mill so that 100 % passes through a 150-μm150 μm sieve and blend the prepared sample
in a cube or cone blender, if necessary to further reduce the heterogeneity of the laboratory sample. Obtain the test samples by
incremental division by mixing the prepared sample and spreading it on a flat non moisture-absorbing surface so that the prepared
sample forms a rectangle of uniform thickness. Divide into at least 20 segments of equal area. With a flat bottom, square-nose tool,
take scoopfuls of approximately equal size from each segment from the full depth of the bed. Combine the scoopfuls to form the
test sample.
NOTE 4—Verify the adequacy of the grind on a separate sub-sample,sub-sample; do not pass the laboratory sample through the 150-μm150 μm sieve.
11. Procedure
11.1 Crucible Preparation:
11.1.1 Add 106 g of fire assay flux mixture to each clay fire assay crucible.
11.1.2 Weigh duplicate test samples: 14.583 g 6 0.001 g. Record the test sample weights.mass. Transfer the test samples to the
fire-assay crucibles.
11.1.3 Mix the contents of the crucible for 2 min in a crucible tumble mixer or perform equivalent flux mixing manually.
11.1.4 Inquartation—Based on the preliminary assay or an estimate, dispense the silver solution over the top portion of the mixed
fire assay clay crucible to achie
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