ASTM D2807-93(2015)
(Test Method)Standard Test Method for Chromic Oxide in Leather (Perchloric Acid Oxidation)
Standard Test Method for Chromic Oxide in Leather (Perchloric Acid Oxidation)
SIGNIFICANCE AND USE
4.1 The procedure described is specific for chromium in leather. Vanadium is the only common interfering element and this is rarely present in quantity. The precision and accuracy of the methods are usually at least as good as the sampling of the leather itself.
4.2 The chromium content of leather relates to the degree of tannage obtained, and hence may be a matter for specification in the purchase of leather. The procedure described provides adequate accuracy for this purpose.
SCOPE
1.1 This test method covers the determination of chromic oxide in leathers that have been partly or completely tanned with chromium compounds. In general the samples will contain between 1 and 5 % chromium, calculated as chromic oxide.
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. See Section 7 for specific safety hazards.
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Designation: D2807 − 93 (Reapproved 2015)
Standard Test Method for
Chromic Oxide in Leather (Perchloric Acid Oxidation)
This standard is issued under the fixed designation D2807; 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 titrated volumetrically with thiosulfate or ferrous salt. The
perchloric acid method requires less manipulation than proce-
1.1 This test method covers the determination of chromic
dures based on fusion of the ash, but care must be taken
oxide in leathers that have been partly or completely tanned
because of potential hazards in the use of this reagent. The
with chromium compounds. In general the samples will con-
perchloric acid method also tends to give low results.
tain between 1 and 5% chromium, calculated as chromic
oxide.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as
4.1 The procedure described is specific for chromium in
standard. No other units of measurement are included in this
leather. Vanadium is the only common interfering element and
standard.
thisisrarelypresentinquantity.Theprecisionandaccuracyof
1.3 This standard does not purport to address all of the
the methods are usually at least as good as the sampling of the
safety concerns, if any, associated with its use. It is the
leather itself.
responsibility of the user of this standard to establish appro-
4.2 Thechromiumcontentofleatherrelatestothedegreeof
priate safety and health practices and determine the applica-
tannage obtained, and hence may be a matter for specification
bility of regulatory limitations prior to use. See Section 7 for
in the purchase of leather. The procedure described provides
specific safety hazards.
adequate accuracy for this purpose.
2. Referenced Documents
5. Apparatus
2.1 ASTM Standards:
5.1 Potentiometric Titration Equipment—Thisisrequiredin
D2617Test Method for Total Ash in Leather
6+
an alternative method for titrating chromium (Cr ) with
D2813Practice for Sampling Leather for Physical and
ferrousammoniumsulfatesolution.Theequipmentconsistsof:
Chemical Tests
5.1.1 Stirrer.
E180Practice for Determining the Precision of ASTM
5.1.2 Calomel and Platinum Electrodes.
Methods for Analysis and Testing of Industrial and Spe-
5.1.3 Potentiometer—A variety of instruments is satisfac-
cialty Chemicals (Withdrawn 2009)
tory. The most convenient common feature of these instru-
ments is a null-point device (either a cathode-ray electron tube
3. Summary of Test Method
or galvanometer) that will signal the abrupt change occurring
3.1 The perchloric acid method is applied to the ash
in the potential when the end point is reached.
obtained in Test Method D2617. In the acid digestion, any
5.2 Incarryingoutthetitration,theelectrodesareimmersed
remaining organic matter is destroyed and the chromium
in the sample, the solution agitated by the stirrer, and the
oxidized to the hexavalent state. On dilution, the chromium is
potential balanced with the galvanometer or cathode-ray tube.
Titrant is added dropwise until a sharp permanent change in
ThistestmethodisunderthejurisdictionofASTMCommitteeD31onLeather
potential occurs.
and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysisThis
test method was developed in cooperation with the American Leather Chemists
6. Reagents
Assn.
Current edition approved Sept. 1, 2015. Published October 2015. Originally
6.1 Purity of Reagents—Reagent grade chemicals shall be
ɛ1
approved in 1969. Last previous edition approved in 2009 as D2807–93 (2009) .
used in all tests. Unless otherwise indicated, it is intended that
DOI: 10.1520/D2807-93R15.
all reagents shall conform to specifications of the Committee
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. Satisfactory equipment include, among others the following: the Kelley,
The last approved version of this historical standard is referenced on Serfass,andFishertritrimeters,Leeds&Northruppotentiometers,andBeckmanpH
www.astm.org. meters.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2807 − 93 (2015)
on Analytical Reagents of the American Chemical Society, 6.8 Potassium Iodide Solution (10 %)—Dissolve 10 g of
where such specifications are available. Other grades may be potassium iodide (KI) in 100 mL of water.
used, provided it is first ascertained that the reagent is of
6.9 Sodium Thiosulfate, Standard Solution (0.1 N)—
sufficiently high purity to permit its use without lessening the
Dissolve 24.85 g of sodium thiosulfate (Na S O ·5H O) in
2 2 3 2
accuracy of the determination.
previously boiled water, add 1 g of sodium carbonate
6.2 Purity of Water—Unless otherwise indicated, reference (Na CO ), and dilute to 1 L.
2 3
towatershallbeunderstoodtomeandistilledwaterorwaterof
6.9.1 Standardization—Dry potassium dichromate
equal purity. (K Cr O )inanovenat130°Cfor2handcoolinadesiccator.
2 2 7
Weigh into a 250-mL glass-stoppered Erlenmeyer flask about
6.3 Ferrous Ammonium Sulfate, Standard Solution (0.1
0.200 g of K Cr O to an accuracy of 0.0001 g. Dissolve in 50
2 2 7
N)—Dissolve 39.21 g of ferrous ammonium sulfate
mLofwater;add4mLofhydrochloricacid(HCl,1+1)20mL
(Fe(NH ) (SO ) ·6H O) in water, add 25 mL of H SO ,
4 2 4 2 2 2 4
ofKIsolution,stoppertheflask,andallowtostand5mininthe
anddilute to 1 L.
dark. Titrate with the thiosulfate solution to be standardized.
6.3.1 Standardization—Dry potassium dichromate
When the color of the solution has faded to a brownish-green,
(K Cr O )inanovenat130°Cfor2handcoolinadesiccator.
2 2 7
add2mLof2%starchsolutionandcontinuetitratinguntilthe
Weigh into a 250-mL glass-stoppered Erlenmeyer flask about
deep blue color changes to a clear green. Record the titration.
0.200 g of K Cr O to an accuracy of 0.0001 g. A beaker is
2 2 7
Calculate the normality of the thiosulfate solution as follows:
preferred if potentiometric titration is used. Dissolve in 75 to
100mLofwater,add20mLofsulfuricacid(H SO ,1+1)and
Normality 5 A/~0.04903 3 B! (2)
2 4
titrate with the ferrous ammonium sulfate solution to be
where:
standardized. Determine the end point either
A = grams of K Cr O used, and
2 2 7
potentiometrically, or with 1,10-phenanthroline ferrous sulfate
6 B = millilitres required for titration.
solution, 0.025 M, as indicator. The potentiometric end point
is marked by a sharp decrease in oxidation potential. The 6.9.2 The thiosulfate solution is quite stable but should be
indicator end point is from blue-green to a red-brown. It is restandardized at least once a month.
preferable not to add the indicator until the end point is
6.10 Starch Indicator Solution, prepared according to ac-
approaching, as evidenced by the disappearance of a
cepted procedures available in analytical handbooks.
yellowish-green color and a gradual change to blue-green.
6.11 Sulfuric Acid (sp gr 1.84)—Concentrated sulfuric acid
6.3.2 The titer of the ferrous ammonium sulfate solution
(H SO ).
2 4
decreases slowly because of oxidation of ferrous iron. This
change may be retarded by storing the solution in a dark bottle
7. Hazards
and by adding a few pieces of mossy tin to the solution.
However, the solution should be standardized daily whenever
7.1 The improper use of HClO can lead to violent and
samples are being analyzed. Calculate the normality of the
serious explosions. In general, these can be traced to situations
ferrous ammonium sulfate solutions as follows:
whereconcentratedHClO hascomeincontactwithorganicor
easily oxidized materials.
Normality 5 A/ 0.04903 3 B (1)
~ !
7.2 The exact procedures given must be followed and the
where:
digestions, once started, should be kept from possible contact
A = grams of K Cr O used, and
2 2 7
wit
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM 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.
´1
Designation: D2807 − 93 (Reapproved 2009) D2807 − 93 (Reapproved 2015)
Standard Test Method for
Chromic Oxide in Leather (Perchloric Acid Oxidation)
This standard is issued under the fixed designation D2807; 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.
ε NOTE—Added research report information to Section 12 editorially in September 2010.
1. Scope
1.1 This test method covers the determination of chromic oxide in leathers that have been partly or completely tanned with
chromium compounds. In general the samples will contain between 1 and 5 % chromium, calculated as chromic oxide.
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. See Section 7 for specific safety hazards.
2. Referenced Documents
2.1 ASTM Standards:
D2617 Test Method for Total Ash in Leather
D2813 Practice for Sampling Leather for Physical and Chemical Tests
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
(Withdrawn 2009)
3. Summary of Test Method
3.1 The perchloric acid method is applied to the ash obtained in Test Method D2617. In the acid digestion, any remaining
organic matter is destroyed and the chromium oxidized to the hexavalent state. On dilution, the chromium is titrated volumetrically
with thiosulfate or ferrous salt. The perchloric acid method requires less manipulation than procedures based on fusion of the ash,
but care must be taken because of potential hazards in the use of this reagent. The perchloric acid method also tends to give low
results.
4. Significance and Use
4.1 The procedure described is specific for chromium in leather. Vanadium is the only common interfering element and this is
rarely present in quantity. The precision and accuracy of the methods are usually at least as good as the sampling of the leather
itself.
4.2 The chromium content of leather relates to the degree of tannage obtained, and hence may be a matter for specification in
the purchase of leather. The procedure described provides adequate accuracy for this purpose.
5. Apparatus
6+
5.1 Potentiometric Titration Equipment—This is required in an alternative method for titrating chromium (Cr ) with ferrous
ammonium sulfate solution. The equipment consists of:
5.1.1 Stirrer.
5.1.2 Calomel and Platinum Electrodes.
This test method is under the jurisdiction of ASTM Committee D31 on Leather and is the direct responsibility of Subcommittee D31.06 on Chemical Analysis This test
method was developed in cooperation with the American Leather Chemists Assn.
Current edition approved April 1, 2009Sept. 1, 2015. Published July 2009October 2015. Originally approved in 1969. Last previous edition approved in 20032009 as
ɛ1
D2807 – 93 (2003).(2009) . DOI: 10.1520/D2807-93R09E01.10.1520/D2807-93R15.
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.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2807 − 93 (2015)
5.1.3 Potentiometer—A variety of instruments is satisfactory. The most convenient common feature of these instruments is a
null-point device (either a cathode-ray electron tube or galvanometer) that will signal the abrupt change occurring in the potential
when the end point is reached.
5.2 In carrying out the titration, the electrodes are immersed in the sample, the solution agitated by the stirrer, and the potential
balanced with the galvanometer or cathode-ray tube. Titrant is added dropwise until a sharp permanent change in potential occurs.
6. Reagents
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to specifications of the Committee on Analytical Reagents of the American Chemical Society, where such
specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean distilled water or water of equal
purity.
6.3 Ferrous Ammonium Sulfate, Standard Solution (0.1 N)—Dissolve 39.21 g of ferrous ammonium sulfate
(Fe(NH ) (SO ) ·6H O) in water, add 25 mL of H SO , anddilute to 1 L.
4 2 4 2 2 2 4
6.3.1 Standardization—Dry potassium dichromate (K Cr O ) in an oven at 130°C for 2 h and cool in a desiccator. Weigh into
2 2 7
a 250-mL glass-stoppered Erlenmeyer flask about 0.200 g of K Cr O to an accuracy of 0.0001 g. A beaker is preferred if
2 2 7
potentiometric titration is used. Dissolve in 75 to 100 mL of water, add 20 mL of sulfuric acid (H SO , 1+1) and titrate with the
2 4
ferrous ammonium sulfate solution to be standardized. Determine the end point either potentiometrically, or with 1,10-
phenanthroline ferrous sulfate solution, 0.025 M, as indicator. The potentiometric end point is marked by a sharp decrease in
oxidation potential. The indicator end point is from blue-green to a red-brown. It is preferable not to add the indicator until the
end point is approaching, as evidenced by the disappearance of a yellowish-green color and a gradual change to blue-green.
6.3.2 The titer of the ferrous ammonium sulfate solution decreases slowly because of oxidation of ferrous iron. This change may
be retarded by storing the solution in a dark bottle and by adding a few pieces of mossy tin to the solution. However, the solution
should be standardized daily whenever samples are being analyzed. Calculate the normality of the ferrous ammonium sulfate
solutions as follows:
Normality 5 A/ 0.04903 3B (1)
~ !
where:
A = grams of K Cr O used, and
2 2 7
B = millilitres required for titration.
6.4 Nitric Acid (sp gr 1.42)—Concentrated nitric acid (HNO ).
6.5 Perchloric Acid (60 percent )—70 or 72 % perchloric acid (HClO ) may be substituted but storage is somewhat more
hazardous.
6.6 1,10-Phenanthroline-Ferrous Sulfate Solution (0.025 M).
6.7 Phosphoric Acid (40 % )—Dilute 45 mL of 85 % phosphoric acid (H PO ) with water to 100 mL.
3 4
6.8 Potassium Iodide Solution (10 %)—Dissolve 10 g of potassium iodide (KI) in 100 mL of water.
6.9 Sodium Thiosulfate, Standard Solution (0.1 N)—Dissolve 24.85 g of sodium thiosulfate (Na S O ·5H O) in previously
2 2 3 2
boiled water, add 1 g of sodium carbonate (Na CO ), and dilute to 1 L.
2 3
6.9.1 Standardization—Dry potassium dichromate (K Cr O ) in an oven at 130°C for 2 h and cool in a desiccator. Weigh into
2 2 7
a 250-mL glass-stoppered Erlenmeyer flask about 0.200 g of K Cr O to an accuracy of 0.0001 g. Dissolve in 50 mL of water;
2 2 7
add 4 mL of hydrochloric acid (HCl, 1+1) 20 mL of KI solution, stopper the flask, and allow to stand 5 min in the dark. Titrate
with the thiosulfate solution to be standardized. When the color of the solution has faded to a brownish-green, add 2 mL of 2 %
starch solution and continue titrating until the deep blue color changes to a clear green. Record the titration. Calculate the normality
of the thiosulfate solution as follows:
Normality 5 A/~0.04903 3B! (2)
where:
A = grams of K Cr O used, and
2 2 7
Satisfactory equipment include, among others the following: the Kelley, Serfass, and Fisher tritrimeters, Leeds & Northrup potentiometers, and Beckman pH meters.
Reagent Chemicals, American Chemical Society Spe
...
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