ASTM D2807-93(2009)
(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
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.
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.
General Information
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:D2807–93 (Reapproved 2009)
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 Department of Defense.
1. Scope perchloric acid method requires less manipulation than proce-
dures based on fusion of the ash, but care must be taken
1.1 This test method covers the determination of chromic
because of potential hazards in the use of this reagent. The
oxide in leathers that have been partly or completely tanned
perchloric acid method also tends to give low results.
with chromium compounds. In general the samples will con-
tain between 1 and 5% chromium, calculated as chromic
4. Significance and Use
oxide.
4.1 The procedure described is specific for chromium in
1.2 The values stated in SI units are to be regarded as
leather. Vanadium is the only common interfering element and
standard. No other units of measurement are included in this
thisisrarelypresentinquantity.Theprecisionandaccuracyof
standard.
the methods are usually at least as good as the sampling of the
1.3 This standard does not purport to address all of the
leather itself.
safety concerns, if any, associated with its use. It is the
4.2 Thechromiumcontentofleatherrelatestothedegreeof
responsibility of the user of this standard to establish appro-
tannage obtained, and hence may be a matter for specification
priate safety and health practices and determine the applica-
in the purchase of leather. The procedure described provides
bility of regulatory limitations prior to use. See Section 7 for
adequate accuracy for this purpose.
specific safety hazards.
5. Apparatus
2. Referenced Documents
2 5.1 Potentiometric Titration Equipment—Thisisrequiredin
2.1 ASTM Standards:
6+
an alternative method for titrating chromium (Cr ) with
D2617 Test Method for Total Ash in Leather
ferrousammoniumsulfatesolution.Theequipmentconsistsof:
D2813 Practice for Sampling Leather for Physical and
5.1.1 Stirrer.
Chemical Tests
5.1.2 Calomel and Platinum Electrodes.
E180 Practice for Determining the Precision of ASTM
5.1.3 Potentiometer—A variety of instruments is satisfac-
Methods for Analysis and Testing of Industrial and Spe-
tory. The most convenient common feature of these instru-
cialty Chemicals
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
in the potential when the end point is reached.
3.1 The perchloric acid method is applied to the ash
5.2 Incarryingoutthetitration,theelectrodesareimmersed
obtained in Test Method D2617. In the acid digestion, any
in the sample, the solution agitated by the stirrer, and the
remaining organic matter is destroyed and the chromium
potential balanced with the galvanometer or cathode-ray tube.
oxidized to the hexavalent state. On dilution, the chromium is
Titrant is added dropwise until a sharp permanent change in
titrated volumetrically with thiosulfate or ferrous salt. The
potential occurs.
6. Reagents
ThistestmethodisunderthejurisdictionofASTMCommitteeD31onLeather
and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysisThis
6.1 Purity of Reagents—Reagent grade chemicals shall be
test method was developed in cooperation with the American Leather Chemists
used in all tests. Unless otherwise indicated, it is intended that
Assn.
Current edition approved April 1, 2009. Published July 2009. Originally
all reagents shall conform to specifications of the Committee
approved in 1969. Last previous edition approved in 2003 as D2807–93 (2003).
DOI: 10.1520/D2807-93R09.
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 Satisfactory equipment include, among others the following: the Kelley,
Standards volume information, refer to the standard’s Document Summary page on Serfass,andFishertritrimeters,Leeds&Northruppotentiometers,andBeckmanpH
the ASTM website. meters.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2807–93 (2009)
on Analytical Reagents of the American Chemical Society, 6.9 Sodium Thiosulfate, Standard Solution (0.1 N)—
where such specifications are available. Other grades may be Dissolve 24.85 g of sodium thiosulfate (Na S O ·5H O) in
2 2 3 2
used, provided it is first ascertained that the reagent is of previously boiled water, add 1 g of sodium carbonate
sufficiently high purity to permit its use without lessening the (Na CO ), and dilute to 1 L.
2 3
accuracy of the determination. 6.9.1 Standardization—Dry potassium dichromate
6.2 Purity of Water—Unless otherwise indicated, reference (K Cr O )inanovenat130°Cfor2handcoolinadesiccator.
2 2 7
towatershallbeunderstoodtomeandistilledwaterorwaterof Weigh into a 250-mL glass-stoppered Erlenmeyer flask about
equal purity. 0.200 g of K Cr O to an accuracy of 0.0001 g. Dissolve in 50
2 2 7
6.3 Ferrous Ammonium Sulfate, Standard Solution (0.1 mLofwater;add4mLofhydrochloricacid(HCl,1+1)20mL
N)—Dissolve 39.21 g of ferrous ammonium sulfate ofKIsolution,stoppertheflask,andallowtostand5mininthe
(Fe(NH ) (SO ) ·6H O) in water, add 25 mL of H SO , dark. Titrate with the thiosulfate solution to be standardized.
4 2 4 2 2 2 4
anddilute to 1 L. When the color of the solution has faded to a brownish-green,
6.3.1 Standardization—Dry potassium dichromate add2mLof2%starchsolutionandcontinuetitratinguntilthe
(K Cr O )inanovenat130°Cfor2handcoolinadesiccator. deep blue color changes to a clear green. Record the titration.
2 2 7
Weigh into a 250-mL glass-stoppered Erlenmeyer flask about Calculate the normality of the thiosulfate solution as follows:
0.200 g of K Cr O to an accuracy of 0.0001 g. A beaker is
2 2 7
Normality 5 A/~0.04903 3 B! (2)
preferred if potentiometric titration is used. Dissolve in 75 to
100mLofwater,add20mLofsulfuricacid(H SO ,1+1)and
2 4
where:
titrate with the ferrous ammonium sulfate solution to be
A = grams of K Cr O used, and
standardized. Determine the end point either potentiometri- 2 2 7
B = millilitres required for titration.
cally, or with 1,10-phenanthroline ferrous sulfate solution,
5 6.9.2 The thiosulfate solution is quite stable but should be
0.025 M, as indicator.The potentiometric end point is marked
restandardized at least once a month.
by a sharp decrease in oxidation potential. The indicator end
6.10 Starch Indicator Solution, prepared according to ac-
point is from blue-green to a red-brown. It is preferable not to
cepted procedures available in analytical handbooks.
add the indicator until the end point is approaching, as
6.11 Sulfuric Acid (sp gr 1.84)—Concentrated sulfuric acid
evidencedbythedisappearanceofayellowish-greencolorand
(H SO ).
2 4
a gradual change to blue-green.
6.3.2 The titer of the ferrous ammonium sulfate solution
7. Hazards
decreases slowly because of oxidation of ferrous iron. This
7.1 The improper use of HClO can lead to violent and
change may be retarded by storing the solution in a dark bottle
serious explosions. In general, these can be traced to situations
and by adding a few pieces of mossy tin to the solution.
whereconcentratedHClO hascomeincontactwithorganicor
However, the solution should be standardized daily whenever
easily oxidized materials.
samples are being analyzed. Calculate the normality of the
7.2 The exact procedures given must be followed and the
ferrous ammonium sulfate solutions as follows:
digestions, once started, should be kept from possible contact
Normality 5 A/~0.04903 3 B! (1)
with other organic matter. The digestions should never
...
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