ASTM D3913-03(2020)e1

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.
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Designation: D3913 − 03 (Reapproved 2020)
Standard Test Method for
Acidity in Basic Chromium Tanning Liquors
This standard is issued under the fixed designation D3913; 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.
ε NOTE—Editorial changes, including standardizing the use of Arabic versus Roman numerals to refer to Procedures 1
and 2, were made in April 2020.
1. Scope and titrated hot to the first appearance of a pink color, stable to
boiling in the supernatant solution, as determined by viewing
1.1 This test method covers the determination of the titrat-
the settled solution against the rim of a porcelain dish, or
able acidity of chromium tanning liquors. By titratable acidity
against the light in a tall beaker or Erlenmeyer flask.
is meant not only free acidity, which is rarely present, but also
anions combined with weakly basic cations such as Chromium
4. Significance and Use
(III),whichcanbetitratedwithbaseatthephenolphthaleinend
4.1 Theacidityofachrometanningliquor,asdeterminedby
point.
this test method, is rarely employed as such. This result is
1.2 The values stated in SI units are to be regarded as
normally combined with the results of a chromium analysis
standard. No other units of measurement are included in this
(seeTest Method D3898) to determine a property of the liquor
standard.
calledbasicity.Thisproperty,equaltothepercentagebywhich
1.3 This standard does not purport to address all of the
anions in a normal chromic salt have been replaced by
safety concerns, if any, associated with its use. It is the
hydroxyl in the solution being analyzed, is closely related to
responsibility of the user of this standard to establish appro-
the tanning behavior of the solution.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5. Interferences
1.4 This international standard was developed in accor-
5.1 Although for most purposes, the results of this analysis
dance with internationally recognized principles on standard-
are intended to give a measure of the acid anions associated
ization established in the Decision on Principles for the
with chromium, it should be mentioned that any weak basic
Development of International Standards, Guides and Recom-
cation will behave similarly. Hence, aluminum, zirconium,
mendations issued by the World Trade Organization Technical
ferric iron, and weak organic bases will all yield salts with
Barriers to Trade (TBT) Committee.
acidity titratable by this test method.Adiscussion of the effect
of these interferences has been published.
2. Referenced Documents
5.2 If there are anions which form very stable complexes
2.1 ASTM Standards:
with chromium present in the solution, the titration:
D3898Test Method for Chromic Oxide in Basic Chromium
x1y23 2 2
~ !
Tanning Liquors
CrOH X H O 1 3 2 x OH (1)
~ ~ ! ! ~ !
x y 2 62x2y
→ 2
3. Summary of Test Method
Cr OH 1yX 1 6 2 x 2 y H O
~ ! ~ !
← 2
3.1 A sample of suitable size is taken by diluting and
where:
aliquoting, if necessary. The sample is then heated to boiling
X = stable complexes,
will not go to completion at the phenolphthalein endpoint
ThistestmethodisunderthejurisdictionofASTMCommitteeD31onLeather andtheacidityreportedwillbelow.Largeexcessofoxalateor
and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysisThis
complexing anions of lesser affinity used for masking effect
test method was developed in cooperation with the American Leather Chemists 4
will introduce this error. To obviate this, an entirely different
Assoc.
method has been developed in which the hydroxyl groups are
Current edition approved April 1, 2020. Published April 2020. Originally
approved in 1991. Last previous edition approved in 2015 as D3913–03 (2015).
titratedandthechromiumiscompletelycomplexedbyoxalate.
DOI: 10.1520/D3913-03R20E01.
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 Hartford, W. H., JALCA, Vol 56, 1961, p. 568.
the ASTM website. Thorstensen, T. C., and Theis, E. R., JALCA, Vol 47, 1952, p. 583.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D3913 − 03 (2020)
This is generally referred to as the Lehigh method and may be phenolphthalein. Boil and titrate while boiling with standard-
5,6
used if complex ions are present in interfering amount. ized0.1Nsodiumhydroxideuntilafaintpinkcolor,asseenat
the side of the casserole after settling, persists for one minute.
6. Reagents and Materials
7.4 Procedure 2—Transferthe25-mLaliquotintoa400-mL
6.1 Purity of Reagents—Reagent grade chemicals shall be
tallbeaker.Diluteto250mL.Heattoboiling,removefromthe
used in all tests. Unless otherwise specified, it is intended that
heat, add 10 drops 5% phenolphthalein and titrate until a pink
all reagents shall conform to the specifications of the Commit-
color is barely noted. Boil again for ten minutes and retitrate
tee onAnalytical Reagents of theAmerican Chemical Society,
until a faint pink color is barely noted on settling. Boil a third
where such specifications are available. Othe
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