ASTM D2868-07

Standard Test Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather

SIGNIFICANCE AND USE
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 %.4  
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.
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. The nitrogen content is used to calculate the hide substance (protein fiber) content of leather.
Note 1—This test method is essentially a composite of Method 6441 of Federal Test Method Standard No. 311 and Method B 5 of the American Leather Chemists Association.
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.

General Information

• Status: Historical
• Publication Date: 31-Mar-2007
• ICS: 59.140.30 - Leather and furs
• Technical Committee: D31 - Leather
• Drafting Committee: D31.06 - Chemical Analysis

Relations

• Replaces: ASTM D2868-96(2001) - Standard Test Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather
• Effective Date: 01-Apr-2007
• Replaced By: ASTM D2868-10 - Standard Test Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather
• Effective Date: 01-Nov-2010
• Referred By: ASTM D6016-17(2023) - Standard Test Method for Determination of Nitrogen, Water Extractable in Leather
• Effective Date: 01-Apr-2007
• Referred By: ASTM D6020-00(2020) - Standard Practice for Calculation of (Non-Mineral) Combined Tanning Agents and Degree of Tannage
• Effective Date: 01-Apr-2007
• Referred By: ASTM D2807-17a - Standard Test Method for Chromic Oxide in Leather (Perchloric Acid Oxidation)
• Effective Date: 01-Apr-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D2868–07
Standard Test Method for
Nitrogen Content (Kjeldahl) and Hide Substance Content of
1
Leather
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. A number 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 Department of Defense.
1. Scope catalyst to convert the nitrogen to ammonium ion. The ammo-
nium ion formed is nonvolatile under these highly acid
1.1 This test method covers the determination of the nitro-
conditions.
gen content of all types of leather. The nitrogen content is used
3.2 Theacidmixtureisthenmadealkalineandtheammonia
tocalculatethehidesubstance(proteinfiber)contentofleather.
liberated is distilled into a boric acid solution which absorbs
NOTE 1—ThistestmethodisessentiallyacompositeofMethod 6441of
the ammonia.
Federal Test Method Standard No. 311 and Method B5 of the American
3.3 The amount of ammonia in the boric acid is then
Leather Chemists Association.
determined by back titration with standardized acid using a
1.2 This standard does not purport to address all of the
sharp color change indicator (green to purple) to determine the
safety concerns, if any, associated with its use. It is the
end point.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 4. Significance and Use
bility of regulatory limitations prior to use.
4.1 The nitrogen content as determined by this test method
is normally considered to be related to the amount of hide
2. Referenced Documents
substance (protein fiber) present in the leather sample.Afactor
2
2.1 ASTM Standards:
of 5.62 is normally used to calculate the hide substance from
D2813 Practice for Sampling Leather for Physical and
the nitrogen content.
Chemical Tests
4.1.1 The 5.62 factor represents the average result of many
E180 Practice for Determining the Precision of ASTM
analyses of animal hides, but it cannot be considered to be
Methods for Analysis and Testing of Industrial and Spe-
accuratesinceitvariessomewhatfromhidetohideofthesame
3
cialty Chemicals
type, from type of hide to type of hide, and also with the
thickness of hide retained in the final leather (split thickness as
3. Summary of Test Method
compared to original hide thickness). As a result of these
3.1 The ground leather specimen prepared according to an
variations, the true factor for any given leather may be
4
accepted procedure is digested with acid in the presence of a 5
expected to vary from 5.44 to 5.80 or about 63%.
4.2 A given leather sample may contain nitrogenous sub-
stances other than hide substance (protein fiber) which will be
1
This test method is under the jurisdiction ofASTM Committee D31 on Leather
analyzed for by this test method, such as resins, dyestuffs, etc.,
and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysis.This
that contain nitrogen. Therefore, although this test method is
test method was developed in cooperation with the American Leather Chemists
Assn. (Standard Method B5 – 1954).
fairly accurate for determining the nitrogen content of leather,
Current edition approved April 1, 2007. Published April 2007. Originally
its use for determining hide substance may result in large
approved in 1970. Last previous edition approved in 2001 as D2868 – 96 (2001).
errors.
DOI: 10.1520/D2868-07.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 4.3 The hide substance value derived from this determina-
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
tion has a large bearing on other chemical determinations of a
Standards volume information, refer to the standard’s Document Summary page on
given leather. Any errors, such as those described in 4.1.1 and
the ASTM website.
3
4.2,willbecarriedoverintotheseotheranalyticalcalculations.
Withdrawn. The last approved version of this historical standard is referenced
on www.astm.org.
4
Acceptable procedures are published in Journal of the American Leather
5
Chemists Association, Vol 51, 1956 p. 497; or Offıcial Methods of Analysis, Am. Dahl, S., “Determination of Hide Substance in the Kjeldahl Method,” in
Leather Chemists Assn., available through the Office of the Secretary-Treasurer, Chemistry and Technology of Leather, Vol 4, Reinhold Publishing Co., New York,
Campus Station, Cincinnati, Ohio 45221; see Practice D2813. NY, 1965.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
D2868–07
5.
...