ASTM D2868-17
(Test Method)Standard Test Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather, Wet Blue and Wet White
Standard Test Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather, Wet Blue and Wet White
SIGNIFICANCE AND USE
4.1 The nitrogen content as determined by this test method is normally considered to be related to the amount of hide substance (protein fiber) present in the leather sample. A factor of 5.62 is normally used to calculate the hide substance from the nitrogen content.
4.1.1 The 5.62 factor represents the average result of many analyses of animal hides, but it cannot be considered to be accurate since it varies somewhat from hide to hide of the same type, from type of hide to type of hide, and also with the thickness of hide retained in the final leather (split thickness as compared to original hide thickness). As a result of these variations, the true factor for any given leather may be expected to vary from 5.44 to 5.80 or about ±3 %.3
4.2 A given leather sample may contain nitrogenous substances other than hide substance (protein fiber) which will be analyzed for by this test method, such as resins, dyestuffs, etc., that contain nitrogen. Therefore, although this test method is fairly accurate for determining the nitrogen content of leather, its use for determining hide substance may result in large errors.
4.3 The hide substance value derived from this determination has a large bearing on other chemical determinations of a given leather. Any errors, such as those described in 4.1.1 and 4.2, will be carried over into these other analytical calculations.
SCOPE
1.1 This test method covers the determination of the nitrogen content of all types of leather, wet blue and wet white. The nitrogen content is used to calculate the hide substance (protein fiber) content of leather, wet blue and wet white.
Note 1: The original test method for leather was essentially a composite of Method 6441 of Federal Test Method Standard No. 311 and Method B5 of the American Leather Chemists Association.
Note 2: Melamine, if present in bonded leather, could give an artificially high value for the calculation of protein fiber.
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 and health 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.
General Information
Relations
Standards Content (Sample)
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.
Designation: D2868 − 17
Standard Test Method for
Nitrogen Content (Kjeldahl) and Hide Substance Content of
1
Leather, Wet Blue and Wet White
This standard is issued under the fixed designation D2868; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope and Wet White for Physical and Chemical Tests
E177Practice for Use of the Terms Precision and Bias in
1.1 This test method covers the determination of the nitro-
ASTM Test Methods
gencontentofalltypesofleather,wetblueandwetwhite.The
E691Practice for Conducting an Interlaboratory Study to
nitrogencontentisusedtocalculatethehidesubstance(protein
Determine the Precision of a Test Method
fiber) content of leather, wet blue and wet white.
NOTE 1—The original test method for leather was essentially a
3. Summary of Test Method
composite of Method6441 of Federal Test Method Standard No. 311 and
Method B5 of the American Leather Chemists Association.
3.1 The specimen prepared according to an accepted proce-
NOTE 2—Melamine, if present in bonded leather, could give an
dure (see Note 3) is digested with acid in the presence of a
artificially high value for the calculation of protein fiber.
catalyst to convert the nitrogen to ammonium ion. The ammo-
1.2 The values stated in SI units are to be regarded as
nium ion formed is nonvolatile under these highly acid
standard. No other units of measurement are included in this
conditions.
standard.
NOTE 3—For leather use specimen prepared per Practice D2813. For
1.3 This standard does not purport to address all of the
wet blue and wet white, use specimen prepared per Practice D6659.
safety concerns, if any, associated with its use. It is the
3.2 Theacidmixtureisthenmadealkalineandtheammonia
responsibility of the user of this standard to establish appro-
liberated is distilled into either a boric acid solution which
priate safety and health practices and determine the applica-
absorbstheammonia,orasulfuricacidsolutionwhichabsorbs
bility of regulatory limitations prior to use.
the ammonia.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.3 When the boric acid solution is used, the amount of
ization established in the Decision on Principles for the
ammonia in the boric acid is then determined by back titration
Development of International Standards, Guides and Recom-
with standardized acid using a sharp color change indicator
mendations issued by the World Trade Organization Technical
(greentopurple)todeterminetheendpoint.Whenthesulfuric
Barriers to Trade (TBT) Committee.
acid solution is used, the amount of ammonia in the sulfuric
acid solution is then determined by back titration with stan-
2. Referenced Documents
dardized base using a sharp color change indicator (purple to
2
green-blue) to determine the end point.
2.1 ASTM Standards:
D2813Practice for Sampling Leather for Physical and
Chemical Tests 4. Significance and Use
D6659Practice for Sampling and Preparation of Wet Blue
4.1 The nitrogen content as determined by this test method
is normally considered to be related to the amount of hide
substance(proteinfiber)presentintheleathersample.Afactor
1
ThistestmethodisunderthejurisdictionofASTMCommitteeD31onLeather
of 5.62 is normally used to calculate the hide substance from
andisthedirectresponsibilityofSubcommitteeD31.06onChemicalAnalysis.This
test method was developed in cooperation with the American Leather Chemists
the nitrogen content.
Assn. (Standard Method B5–1954).
4.1.1 The 5.62 factor represents the average result of many
Current edition approved April 1, 2017. Published May 2017. Originally
analyses of animal hides, but it cannot be considered to be
approved in 1970. Last previous edition approved in 2015 as D2868–10 (2015).
DOI: 10.1520/D2868-17.
accuratesinceitvariessomewhatfromhidetohideofthesame
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
type, from type of hide to type of hide, and also with the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
thicknessofhideretainedinthefinalleather(splitthicknessas
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. compared to original hide thickness). As a result of these
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