ASTM D3913-03(2015)
(Test Method)Standard Test Method for Acidity in Basic Chromium Tanning Liquors
Standard Test Method for Acidity in Basic Chromium Tanning Liquors
SIGNIFICANCE AND USE
4.1 The acidity of a chrome tanning liquor, as determined by this test method, is rarely employed as such. This result is normally combined with the results of a chromium analysis (see Test Method D3898) to determine a property of the liquor called basicity. This property, equal to the percentage by which anions in a normal chromic salt have been replaced by hydroxyl in the solution being analyzed, is closely related to the tanning behavior of the solution.
SCOPE
1.1 This test method covers the determination of the titratable acidity of chromium tanning liquors. By titratable acidity is meant not only free acidity, which is rarely present, but also anions combined with weakly basic cations such as Chromium (III), which can be titrated with base at the phenolphthalein end point.
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: D3913 − 03 (Reapproved 2015)
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.
1. Scope (seeTest Method D3898) to determine a property of the liquor
calledbasicity.Thisproperty,equaltothepercentagebywhich
1.1 This test method covers the determination of the titrat-
anions in a normal chromic salt have been replaced by
able acidity of chromium tanning liquors. By titratable acidity
hydroxyl in the solution being analyzed, is closely related to
is meant not only free acidity, which is rarely present, but also
the tanning behavior of the solution.
anions combined with weakly basic cations such as Chromium
(III),whichcanbetitratedwithbaseatthephenolphthaleinend
5. Interferences
point.
5.1 Although for most purposes, the results of this analysis
1.2 The values stated in SI units are to be regarded as
are intended to give a measure of the acid anions associated
standard. No other units of measurement are included in this
with chromium, it should be mentioned that any weak basic
standard.
cation will behave similarly. Hence, aluminum, zirconium,
1.3 This standard does not purport to address all of the
ferric iron, and weak organic bases will all yield salts with
safety concerns, if any, associated with its use. It is the
acidity titratable by this test method.Adiscussion of the effect
responsibility of the user of this standard to establish appro- 3
of these interferences has been published.
priate safety and health practices and determine the applica-
5.2 If there are anions which form very stable complexes
bility of regulatory limitations prior to use.
with chromium present in the solution, the titration:
2. Referenced Documents
~x1y23!2 2
~CrOH X ~H O! ! 1~3 2 x!OH (1)
x y 2 62x2y
2.1 ASTM Standards:
→ 2
Cr OH 1yX 1 6 2 x 2 y H O
~ ! ~ !
D3898Test Method for Chromic Oxide in Basic Chromium ← 3 2
Tanning Liquors
where:
X = stable complexes,
3. Summary of Test Method
will not go to completion at the phenolphthalein endpoint
3.1 A sample of suitable size is taken by diluting and
andtheacidityreportedwillbelow.Largeexcessofoxalateor
aliquoting, if necessary. The sample is then heated to boiling
complexing anions of lesser affinity used for masking effect
and titrated hot to the first appearance of a pink color, stable to
will introduce this error. To obviate this, an entirely different
boiling in the supernatant solution, as determined by viewing
method has been developed in which the hydroxyl groups are
the settled solution against the rim of a porcelain dish, or
titratedandthechromiumiscompletelycomplexedbyoxalate.
against the light in a tall beaker or Erlenmeyer flask.
This is generally referred to as the Lehigh method and may be
5,6
used if complex ions are present in interfering amount.
4. Significance and Use
4.1 Theacidityofachrometanningliquor,asdeterminedby
6. Reagents and Materials
this test method, is rarely employed as such. This result is
normally combined with the results of a chromium analysis 6.1 Purity of Reagents—Reagent grade chemicals shall be
used in all tests. Unless otherwise specified, it is intended that
all reagents shall conform to the specifications of the Commit-
ThistestmethodisunderthejurisdictionofASTMCommitteeD31onLeather
tee onAnalytical Reagents of theAmerican Chemical Society,
and is the direct responsibility of Subcommittee D31.06 on ChemicalAnalysisThis
test method was developed in cooperation with the American Leather Chemists
Assoc.
Current edition approved Sept. 1, 2015. Published October 2015. Originally
approved in 1991. Last previous edition approved in 2009 as D3913–03 (2009). Hartford, W. H., JALCA, Vol 56, 1961, p. 568.
DOI: 10.1520/D3913-03R15. Thorstensen, T. C., and Theis, E. R., JALCA, Vol 47, 1952, p. 583.
2 5
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Theis, E. R., and Thorstensen , T. C., Journal International Society Leather
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Trade Chemists, Vol 31, 1947, p. 124.
Standards volume information, refer to the standard’s Document Summary page on Serfass, E. J., Theis, E. R., and Clark, A., Jr., The Journal of the Leather
the ASTM website. Chemists Association, Vol 42, 1947, p. 360.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3913 − 03 (2015)
where such specifications are available. Other grades may be heat, add 10 drops 5% phenolphthalein and titrate until a pink
used, provided it is first ascertained that the reagent is of color is barely noted. Boil again for ten minutes and retitrate
sufficient high purity to permit its use without lessening the until a faint pink color is barely noted on settling. Boil a third
accuracy of the determination. timeandcompletethetitration.(Theprocessmaybeexpedited
byusingtwo,preferablythree,aliquotsofthesample,inwhich
6.2 Purity of Water—Unless otherwise specified, reference
oneistitratedaccordingtotheaboveprocedur
...
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.
Designation: D3913 − 03 (Reapproved 2009) D3913 − 03 (Reapproved 2015)
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of the titratable acidity of chromium tanning liquors. By titratable acidity is
meant not only free acidity, which is rarely present, but also anions combined with weakly basic cations such as Chromium (III),
which can be titrated with base at the phenolphthalein end point.
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
2.1 ASTM Standards:
D3898 Test Method for Chromic Oxide in Basic Chromium Tanning Liquors
3. Summary of Test Method
3.1 A sample of suitable size is taken by diluting and aliquoting, if necessary. The sample is then heated to boiling and titrated
hot to the first appearance of a pink color, stable to boiling in the supernatant solution, as determined by viewing the settled solution
against the rim of a porcelain dish, or against the light in a tall beaker or Erlenmeyer flask.
4. Significance and Use
4.1 The acidity of a chrome tanning liquor, as determined by this test method, is rarely employed as such. This result is normally
combined with the results of a chromium analysis (see Test Method D3898) to determine a property of the liquor called basicity.
This property, equal to the percentage by which anions in a normal chromic salt have been replaced by hydroxyl in the solution
being analyzed, is closely related to the tanning behavior of the solution.
5. Interferences
5.1 Although for most purposes, the results of this analysis are intended to give a measure of the acid anions associated with
chromium, it should be mentioned that any weak basic cation will behave similarly. Hence, aluminum, zirconium, ferric iron, and
weak organic bases will all yield salts with acidity titratable by this test method. A discussion of the effect of these interferences
has been published.
5.2 If there are anions which form very stable complexes with chromium present in the solution, the titration:
~x1y23!2 2
CrOH X H O 1 32 x OH (1)
~ ~ ! ! ~ !
x y 2
62x2y
→ 2
Cr~OH! 1yX 1~62 x 2 y!H O
← 2
where:
X = stable complexes,
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 Assoc.
Current edition approved April 1, 2009Sept. 1, 2015. Published July 2009October 2015. Originally approved in 1991. Last previous edition approved in 20032009 as
D3913 – 03.D3913 – 03 (2009). DOI: 10.1520/D3913-03R09.10.1520/D3913-03R15.
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.
Hartford, W. H., JALCA, Vol 56, 1961, p. 568.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3913 − 03 (2015)
will not go to completion at the phenolphthalein endpoint and the acidity reported will be low. Large excess of oxalate or
complexing anions of lesser affinity used for masking effect will introduce this error. To obviate this, an entirely different method
has been developed in which the hydroxyl groups are titrated and the chromium is completely complexed by oxalate. This is
5,6
generally referred to as the Lehigh method and may be used if complex ions are present in interfering amount.
6. Reagents and Materials
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise specified, it is intended that all
reagents shall conform to the 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 sufficient high
purity to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water—Unless otherwise specified, reference to water shall be understood to mean distilled water or water of equal
purity.
6.3 Sodium Hydroxide, 0.1 N—Dissolve 42 g NaOH in about 60 mL water. Cool and transfer to a 100-mL volumetric flask;
dilute to the mark, stopper, mix, and allow any turbidity to settle. Pipet 10 mL of the clear solution to a 1-L volumetric flask; dilute
to mark and mix well. Keep stoppered and protected from atmospheric carbon dioxide.
6.3.1 Standardization—Dry potassium hydrogen phthalate, KHC H O , in an oven for 2 h at 120°C and cool in desiccator
...
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