ASTM D2868-10
(Test Method)Standard Test Method for Nitrogen Content (Kjeldahl) and Hide Substance Content of Leather
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.
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 %.
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, 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.
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Designation: D2868 − 10
StandardTest 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. 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 U.S. Department of Defense.
1. Scope 3. Summary of Test Method
3.1 The specimen prepared according to an accepted proce-
1.1 This test method covers the determination of the nitro-
dure (see Note 3) is digested with acid in the presence of a
gen content of all types of leather, wet blue and wet white.The
catalyst to convert the nitrogen to ammonium ion. The ammo-
nitrogencontentisusedtocalculatethehidesubstance(protein
nium ion formed is nonvolatile under these highly acid
fiber) content of leather, wet blue and wet white.
conditions.
NOTE 1—The original test method for leather was essentially a
NOTE 3—For leather use specimen prepared per Practice D2813. For
composite of Method 6441 of Federal Test Method Standard No. 311 and
wet blue and wet white, use specimen prepared per Practice D6659.
Method B5 of the American Leather Chemists Association.
3.2 Theacidmixtureisthenmadealkalineandtheammonia
NOTE 2—Melamine, if present in bonded leather, could give an
artificially high value for the calculation of protein fiber. liberated is distilled into either a boric acid solution which
absorbs the ammonia, or a sulfuric acid solution which absorbs
1.2 The values stated in SI units are to be regarded as
the ammonia.
standard. No other units of measurement are included in this
standard.
3.3 When the boric acid solution is used, the amount of
ammonia in the boric acid is then determined by back titration
1.3 This standard does not purport to address all of the
with standardized acid using a sharp color change indicator
safety concerns, if any, associated with its use. It is the
(green to purple) to determine the end point. When the sulfuric
responsibility of the user of this standard to establish appro-
acid solution is used, the amount of ammonia in the sulfuric
priate safety and health practices and determine the applica-
acid solution is then determined by back titration with stan-
bility of regulatory limitations prior to use.
dardized base using a sharp color change indicator (purple to
green-blue) to determine the end point.
2. Referenced Documents
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4. Significance and Use
2.1 ASTM Standards:
D2813 Practice for Sampling Leather for Physical and
4.1 The nitrogen content as determined by this test method
Chemical Tests
is normally considered to be related to the amount of hide
D6659 Practice for Sampling and Preparation of Wet Blue
substance (protein fiber) present in the leather sample.Afactor
for Physical and Chemical Tests
of 5.62 is normally used to calculate the hide substance from
E177 Practice for Use of the Terms Precision and Bias in
the nitrogen content.
ASTM Test Methods
4.1.1 The 5.62 factor represents the average result of many
E691 Practice for Conducting an Interlaboratory Study to
analyses of animal hides, but it cannot be considered to be
Determine the Precision of a Test Method
accuratesinceitvariessomewhatfromhidetohideofthesame
type, from type of hide to type of hide, and also with the
thickness of hide retained in the final leather (split thickness as
1 compared to original hide thickness). As a result of these
This test method is under the jurisdiction ofASTM Committee D31 on Leather
and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysis.This
variations, the true factor for any given leather may be
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test method was developed in cooperation with the American Leather Chemists
expected to vary from 5.44 to 5.80 or about 63%.
Assn. (Standard Method B5 – 1954).
Current edition approved Nov. 1, 2010. Published December 2010. Originally
4.2 A given leather sample may contain nitrogenous sub-
approved in 1970. Last previous edition approved in 2007 as D2868 – 07. DOI:
stances other than hide substance (protein fiber) which will be
10.1520/D2868-10.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Dahl, S., “Determination of Hide Substance in the Kjeldahl Method,” in
Standards volume information, refer to the standard’s Document Summary page on Chemistry and Technology of Leather, Vol 4, Reinhold Publishing Co., New York,
the ASTM website. NY, 1965.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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This document is not anASTM standard and is intended only to provide the user of anASTM 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:D2868–07 Designation:D2868–10
Standard Test Method for
Nitrogen Content (Kjeldahl) and Hide Substance Content of
LeatherNitrogen Content (Kjeldahl) and Hide Substance
1
Content of 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. 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
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.
NOTE1—This test method is essentially a composite of Method6441 of FederalTest Method Standard No. 311 and Method B5 of theAmerican Leather
Chemists Association.
1.2 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D2813 Practice for Sampling Leather for Physical and Chemical Tests
D6659 Practice for Sampling and Preparation of Wet Blue for Physical and Chemical Tests
E180Practice for Determining the Precision ofASTM Methods forAnalysis and Testing of Industrial and Specialty Chemicals
177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Summary of Test Method
3.1The ground leather specimen prepared according to an accepted procedure is digested with acid in the presence of a catalyst
to convert the nitrogen to ammonium ion. The ammonium ion formed is nonvolatile under these highly acid conditions.
3.2The acid mixture is then made alkaline and the ammonia liberated is distilled into a boric acid solution which absorbs the
ammonia.
3.3The amount of ammonia in the boric acid is then determined by back titration with standardized acid using a sharp color
change indicator (green to purple) to determine the end point.
3.1 The specimen prepared according to an accepted procedure (see Note 3) is digested with acid in the presence of a catalyst
to convert the nitrogen to ammonium ion. The ammonium ion formed is nonvolatile under these highly acid conditions.
NOTE 3—For leather use specimen prepared per Practice D2813. For wet blue and wet white, use specimen prepared per Practice D6659.
3.2 The acid mixture is then made alkaline and the ammonia liberated is distilled into either a boric acid solution which absorbs
the ammonia, or a sulfuric acid solution which absorbs the ammonia.
3.3 When the boric acid solution is used, the amount of ammonia in the boric acid is then determined by back titration with
1
This test method is under the jurisdiction ofASTM Committee D31 on Leather and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysis. This test
method was developed in cooperation with the American Leather Chemists Assn. (Standard Method B5 – 1954).
Current edition approved AprilNov. 1, 2007.2010. Published April 2007.December 2010. Originally approved in 1970. Last previous edition approved in 20012007 as
D2868–96(2001).D2868 – 07. DOI: 10.1520/D2868-107.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM 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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D2868–10
standardizedacidusingasharpcolorchangeindicator(greentopurple)todeterminet
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