ASTM E1335-96(2000)e1
(Test Method)Standard Test Methods for Determination of Gold in Bullion by Cupellation
Standard Test Methods for Determination of Gold in Bullion by Cupellation
SCOPE
1.1 These test methods cover cupellation analysis of bullion having chemical compositions within the following limits:ElementConcentration Range, %Gold 0.5 to 4.0 and 20.0 to 99.0Silver 1.0 to 99.5Total gold plus silver75.0 to 100.0
1.2 These test methods appear in the following order: Sections10-1620.0-99.0 % gold0.5-4.0 % gold17-21
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. For specific safety hazards, see Section 9.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: E 1335 – 96 (Reapproved 2000)
Standard Test Methods for
Determination of Gold in Bullion by Cupellation
This standard is issued under the fixed designation E 1335; 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.
e NOTE—Editorial corrections were made throughout in November 2000.
1. Scope E 882 Guide for Accountability and Quality Control in the
Chemical Analysis Laboratory
1.1 These test methods cover cupellation analysis of bullion
having chemical compositions within the following limits:
3. Terminology
Element Concentration Range, %
3.1 Definitions:
Gold 0.5 to 4.0 and 20.0 to 99.0
3.1.1 annealing—a thermal treatment to change the proper-
Silver 1.0 to 99.5
ties or grain structure of the product.
Total gold plus silver 75.0 to 100.0
3.1.2 cupel—a small, shallow, porous cup, usually made of
1.2 These test methods appear in the following order:
bone ash or magnesite.
Sections
3.1.3 cupellation—an oxidizing fusion of lead, gold, and
silver in a cupel. The lead is oxidized to litharge (PbO); other
10-1620.0–99.0 %
gold base metals which may be present, such as copper and tin, are
0.5–4.0 % gold 17-21
oxidized as well. The oxidized metals are absorbed into the
cupel, leaving a gold and silver doré bead on the cupel surface.
1.3 This standard does not purport to address all of the
3.1.4 doré bead—a gold and silver alloy bead which results
safety concerns, if any, associated with its use. It is the
from cupellation.
responsibility of the user of this standard to establish appro-
3.1.5 inquartation—the addition of silver to an assay
priate safety and health practices and determine the applica-
sample to facilitate parting.
bility of regulatory limitations prior to use. For specific safety
3.1.6 parting—separating silver from gold by selectively
hazards, see Section 9.
dissolving the silver in acid, usually nitric acid.
2. Referenced Documents
3.1.7 proof—a synthetic standard having a composition
similar to the test sample.
2.1 ASTM Standards:
3.1.8 proof correction—analyzing the proof concurrently
B 562 Specification for Refined Gold
with the test sample and using the results to correct the final
E 29 Practice for Using Significant Digits in Test Data to
assay.
Determine Conformance with Specifications
3.1.9 For definitions of other terms, refer to Terminology
E 50 Practices for Apparatus, Reagents, and Safety Precau-
E 135.
tions for Chemical Analysis of Metals
E 135 Terminology Relating to Analytical Chemistry for
4. Significance and Use
Metals, Ores, and Related Materials
4.1 These test methods are intended for the determination of
E 173 Practice for Conducting Interlaboratory Studies of
the gold content of gold and silver bullion. It is assumed that all
Methods for Chemical Analysis of Metals
who use these test methods are trained assayers capable of
performing common fire assay procedures skillfully and safely.
These test methods are under the jurisdiction of ASTM Committee E-1 on
It is expected that work will be performed in a properly
Analytical Chemistry for Metals, Ores, and Related Materials and are the direct
equipped laboratory.
responsibility of Subcommittee E01.03 on Precious Metals.
Current edition approved April 10, 1996. Published August 1996. Originally
published as E 1335 – 90. Last previous edition E 1335 – 94.
Annual Book of ASTM Standards, Vol 02.04.
Annual Book of ASTM Standards, Vol 14.02.
4 6
Annual Book of ASTM Standards, Vol 03.05. Supporting data are available from ASTM Headquarters. Request RR:E01-
Annual Book of ASTM Standards, Vol 03.06. 1010.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1335
5. Interferences 9.4 Drillings are not usually representative of a melt. If bar
drillings are to be analyzed, obtain them as directed in
5.1 If the bullion contains any of the following elements in
Specification B 562.
excess of the concentrations shown, the accuracy and precision
requirements of these test methods may not be achieved.
TEST METHOD A
Element Maximum Level, %
Arsenic 2.0
10. Scope
Antimony 2.0
Bismuth 2.0 10.1 This test method covers cupellation analysis of gold in
Iron 2.0
bullion containing 20.0 to 99.0 % gold and 1.0 to 80.0 % silver.
Nickel 2.0
Platinum group, total (Ir, Os, Pd, Pt, Rh, Ru) 0.01
Selenium 2.0
11. Summary of Test Method
Tellurium 2.0
11.1 A preliminary assay is performed to estimate the
Thallium 2.0
Tungsten 0.5
approximate gold content and approximate gold plus silver
Zinc 5.0
content. The sample is weighed and silver or copper, or both,
added if necessary. The sample is wrapped in lead foil and
6. Apparatus
cupelled to remove base metals, then parted in nitric acid. The
6.1 Assay Furnace—Capable of temperatures up to 1100°C,
insoluble portion is weighed to determine the gold content.
accurate to 610°C, with draft controls.
Proof standards are used for correction of systematic gravimet-
6.2 Cupels—Magnesite (MgCO ) or bone ash.
3 ric errors.
6.3 Hammer.
6.4 Hammering Block.
12. Approximate Assay
6.5 Rolling Mill.
12.1 Perform a preliminary assay first on the test sample to
6.6 Analytical Balance—Capable of weighing to 0.01 mg.
establish a suitable composition for the proof correction
standard.
7. Reagents
12.2 Approximate Gold Plus Silver Content—Weigh one
7.1 Copper Metal, 99.9 % purity, minimum.
500 6 2-mg sample to the nearest 0.1 mg. Weigh a portion of
7.2 Gold Metal, 99.99 % purity, minimum.
lead foil in accordance with the following:
7.3 Lead Foil, 99.99 % purity, min (0.001 % silver, maxi-
Estimated Total Gold Plus Silver, % Weight of Lead Foil, g
mum).
95.0–100.0 5.0
7.4 Silver Metal, 99.9 % purity, min (0.001 % gold, maxi-
90.0–95.0 10.0
mum).
12.2.1 Wrap the sample in the lead foil.
12.2.2 Cupellation—After the lead foil packets are pre-
8. Hazards
pared, place them in the assay furnace on cupels which have
8.1 For precautions to be observed in the use of certain
been preheated to 900°C for 10 min with the draft slightly
reagents and equipment these test methods refer to Practices
open. For proof-corrected assays, alternate samples and the
E 50.
corresponding proofs. The furnace temperature is correct if the
8.2 Use care when handling hot crucibles and operating
dark crust which forms over the melted lead packet disappears
furnaces to avoid personal injury by either burn or electrical
within a few minutes. A typical temperature to produce such
shock.
reasonably rapid“ opening up” of the samples is 900°C.
8.3 Lead and litharge (PbO) are toxic materials and are
12.2.3 After the lead packets have opened up adjust the
volatile at low temperatures. Avoid inhalation, ingestion, or
airflow through the furnace. The temperature must be main-
skin contact.
tained high enough to prevent the button from freezing (the
solidification of molten litharge on the button surface).
9. Sampling
12.2.4 Keep the cupels in the furnace until all traces of lead
9.1 Use shot or pin tube samples. Brush the samples to
have disappeared. This time depends on the amount of lead
remove any adhering glass or flux.
used, the furnace temperature, and the airflow (Note 1).
9.2 Prepare shot samples from molten metal poured into
Remove the cupels and cool them to room temperature.
water. Use only whole single pieces between 1 and 3 mm in
NOTE 1—Occasionally at the end of the cupellation process, the beads
diameter.
will visibly brighten or “flash.” This is a result of the sudden release of the
9.3 Pin tube samples are prepared from molten metal drawn
latent heat of fusion as the lead-free bead solidifies.
into vacuum-evacuated glass tubes. Break the glass and inspect
12.2.5 Remove the test sample doré beads from the cupels
the samples to ensure that they are not hollow and that they are
and clean any adhering cupel material from them with a stiff
free from slag and inclusions.
brush.
9.3.1 Roll the samples lengthwise on a clean rolling mill to
12.2.6 Weigh the doré bead to the nearest 0.1 mg and
0.127 mm (0.005 in.), then clean them with alcohol.
calculate the approximate gold plus silver content as follows:
9.3.2 Cut the strip into horizontal slices to obtain the desired
sample weight. T 5 ~D/V! 3 100 (1)
a
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
E 1335
13. Proof Standard Preparation
where:
T = approximate total gold plus silver, %,
a 13.1 Prepare two proof standards, each containing gold,
D = weight of the doré bead, g, and
silver, and copper in the amounts listed as follows. Wrap each
V = weight of the sample, g.
proof in lead foil in accordance with 12.2 and proceed to
12.3 Approximate Gold Content—Weigh one 500 6 2-mg
12.2.2.
test sample to the nearest 0.1 mg. Add 1.25 6 0.05 g of
13.1.1 Gold—The weight of gold must be within 65mgof
inquarting silver and 0.05 6 0.010 g copper. Wrap the sample
the approximate gold content (12.3). Weigh the gold to the
with additions in lead foil as directed in 12.2.
nearest 0.01 mg and use this weight for calculating the proof
12.3.1 Cupel as directed in 12.2.2-12.2.4.
correction (15.3).
12.3.2 Remove the test samples and any proof beads from
13.1.2 Silver—The weight of inquarting silver is 2.5 times
the cupels, place them on edge and tap them lightly with a
the approximate gold content (12.3). Weigh the silver to the
hammer to loosen any adhering cupel material. Remove the
nearest 10 mg.
remaining traces of cupel material with a stiff brush.
13.1.3 Copper—If the approximate base metal content
12.3.3 Form Coronet—Flatten the beads for the gold deter-
(12.5) of the sample is less than 1 %, add 0.056 0.01 g of
mination on an anvil with a hammer and taper the edges to
copper metal to each proof. If the approximate base metal
facilitate rolling.
content is greater than 1 %, the amount of copper is equal to the
12.3.4 Anneal the flattened beads to a temperature of 650 to
approximate base metal content. Weigh the copper to the
700°C. Pass the beads through a rolling mill to form an
nearest 10 mg.
elongated strip about 10 cm long and 0.005 to 0.01 cm in
13.1.4 Cupel the proof standards together with the test
thickness, maintaining a uniform thickness throughout the
samples (14.2) as directed in 12.2.2.
batch of samples. Reanneal the strips and then roll each into a
loose spiral (or coronet) with the bottom side facing outward.
14. Procedure
12.3.5 Parting:
14.1 Proof Correcte
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.