ASTM E194-20

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of the standard as published by ASTM is to be considered the official document.
Designation: E194 − 10 (Reapproved 2015) E194 − 20
Standard Test Method for
Acid-Insoluble Content of Copper and Iron Powders
This standard is issued under the fixed designation E194; 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 Scope*
1.1 This test method covers the determination of the mineral-acid-insoluble matter content of copper and iron powders in amounts
under 1.0 %.
1.2 Units—With the exception of the values for density and the mass used to determine density, for which the use of the gram per
cubic centimetre (g/cm ) and gram (g) units is the longstanding industry practice, the values stated in SI units are to be regarded
as standard.
1.3 This standard does not purport to address all of the safety problems,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.
1.4 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:
B215 Practices for Sampling Metal Powders
E50 Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Summary of Test Method
3.1 The sample is dissolved in the appropriate acid: nitric acid (HNO ) for copper, hydrochloric acid (HCl) for iron. The insoluble
matter is filtered out and ignited in a furnace at 980 °C for 1 h.
4. Significance and Use
4.1 The purpose of this test method is to determine the amount of gangue, refractory, inert, etc.,etc. materials, that may adversely
affect compacting tools and sintered properties of components formed from copper and iron powders.
This test method is under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee B09.02
on Base Metal Powders.
Current edition approved Oct. 1, 2015Oct. 1, 2020. Published June 2010October 2020. Originally approved in 1962. Last previous edition approved in 20102015 as
E194 – 10.E194 – 10(2015). DOI: 10.1520/E0194-10R15.10.1520/E0194-20.
Based on the method developed by the Metal Powder Association (now the Metal Powder Producers Association of the Metal Powder Industries Federation) and described
in MPIF Standard 06, “Determination of Acid Insoluble Matter in Iron and Copper Powders,” which is a standard of the MPIF.
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.
*A Summary of Changes section appears at the end of this standard
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E194 − 20
4.2 The insoluble matter consists of those nonmetallic substances that do not dissolve in the mineral acid used to dissolve the
metal. In copper powder, which is treated with nitric acid, the acid-insoluble matter includes silica, insoluble silicates, alumina,
clays, and other refractory materials that may be introduced either as impurities in the raw material or from the furnace lining, fuel,
etc.; lead sulfate may also be present. In iron powder, which is treated with hydrochloric acid, the insoluble matter may include
carbides in addition to the substances listed above. The test method excludes insoluble material that is volatile at the ignition
temperature specified.
5. Interferences
5.1 Any metallic tin present in the copper powder will be converted into the insoluble tin oxide by the nitric acid treatment; in
such cases, provision shall be made for the determination of tin oxide and the appropriate correction applied.
6. Apparatus
6.1 Apparatus and reagents shall conform to the requirements prescribed in Practices E50.
6.2 Hot Plate.
6.3 Muffle Furnace, capable of operating at 980 °C.
6.4 Casseroles (non-metallic), 250 mL and 750 mL.
6.5 Glass Funnel.
6.6 Quart or Porcelain Crucible.
6.7 Desiccator.
6.8 Analytical Balance, having a sensitivity of 0.1 mg.readable to 0.0001 g, with a minimum capacity of 100 g.
6.9 Filter Paper, Whatman No. 541 or one of equivalent pore size and ash content.
6.10 Vapor Collection System, suitable to provide adequate operator protection from chemical vapors resulting from the acid
digestion steps and muffle furnace ignition steps.
7. Reagents
7.1 Hydrochloric Acid HCl (1:1).
7.2 Hydrochloric Acid HCl (1:25).
7.3 Nitric Acid (HNO ).
7.4 Nitric Acid HNO (1:1).
7.5 Ammonium Iodide (NH I).
7.6 Potassium Thiocyanate (5%).(5 %).
8. Sampling
8.1 The metal powder shall be sampled in accordance with Practices B215.
E194 − 20
8.2 Store the test sample in a tightly stoppered bottle to protect it from moisture which promotes oxidation of copper and iron.
COPPER POWDER
8.3 The test portion shall be approximately 5 g of metal powder.
COPPER POWDER
9. Procedure
9.1 Transfer 5 gDetermine the mass of the sample, weighed to the nearest 0.0001 g, to a 250 mL test portion to 0.0001 g and
transfer to a 250 mL covered casserole.
NOTE 1—Some operators report better reproducibility when increasing the metal powder sample size to 10 g. Nevertheless, the precision statement listed
in Section 14 was based on 5 g samples.
9.2 Add 100 mL of HNO (1:1) and let stand at room temperature until the reaction is complete.
9.3 Place the casserole on a hot plate and boil until the volume is reduced to 50 mL.
9.4 Cool, dilute with distilled water to about 100 mL, and bring to a boil. Maintain boiling for about 1 min.
9.5 Filter the hot solution, and wash with hot distilled water until all traces of blue color (copper salts) disappear.
9.6 Prepare a quartz or porcelain crucible by pre-heating for 40 min in air at 980 °C and then cool it in a desiccator.
9.7 Weigh the crucible to the nearest 0.0001 g.and determine the mass to 0.0001 g.
9.8 Transfer the filter paper and residue to the crucible.
9.9 Dry, Dry in an oven at 105 °C for
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