ASTM D6410-99
(Test Method)Standard Test Method for Determining Acidity of Vegetable Tanning Liquors
Standard Test Method for Determining Acidity of Vegetable Tanning Liquors
SCOPE
1.1 This test method covers determining the acidity of tannery liquors made up from vegetable tanning materials.
1.2 The values stated in SI units are to be regarded as the 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: D 6410 – 99
Standard Test Method for
Determining Acidity of Vegetable Tanning Liquors
This standard is issued under the fixed designation D 6410; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope test method provides a standard procedure for determining the
total acidity for any sample of vegetable tanning liquor.
1.1 This test method covers determining the acidity of
5.2 The specimens are aliquots from the analytical solution
tannery liquors made up from vegetable tanning materials.
prepared from the sample of tannery liquor collected for this
1.2 The values stated in SI units are to be regarded as the
purpose.
standard.
5.3 The total acidity of the liquor sample is determined by
1.3 This standard does not purport to address all of the
one of two titrametric procedures described in this test method.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
6. Apparatus and Reagents
priate safety and health practices and determine the applica-
6.1 Analytical Solution:
bility of regulatory limitations prior to use.
6.1.1 Flask, 1 L volumetric. Class A flasks with a bulb in the
2. Referenced Documents neck (M.C.A. type) are especially suitable for this work.
6.1.2 Hydrometer, preferably with a Barkometer scale (that
2.1 ASTM Standards:
is, a scale calibrated in °Bk). The three digits to the right of the
D 6404 Practice for Sampling Vegetable Materials Contain-
decimal point on a standard specific gravity reading are equal
ing Tannin
to the Barkometer scale reading. That is, a sp.gr. of 1.200
2.2 ALCA Methods:
equals 200°Bk and a sp.gr. of 1.020 equals 20°Bk.
A25 Analysis of Tannery Liquors
6.2 Acidity Determination—Method I:
3. Terminology 6.2.1 Graduated Cylinder, glass-stoppered, graduated to
contain 250 mL.
3.1 Definitions:
6.2.2 Gelatin Solution, 1 %, neutral to bromocresol purple.
3.1.1 tannery liquor—water solutions containing vegetable
The addition of 25 mL of 95 % ethyl alcohol per litre is
tannin that are made up and used in a vegetable tannery.
recommended to prevent frothing. The solution shall be ad-
4. Summary of Test Method
justed to neutrality to bromocresol purple with 0.1 N acetic
acid or 0.1 N sodium hydroxide.
4.1 An analytical solution is prepared from the sample of
6.2.3 Kaolin , acid-washed kaolin clay which conforms to
tannery liquor (Practice D 6404). Specimen aliquots from this
the following specifications:
analytical solution are then analyzed for total acidity by one of
6.2.3.1 Suspend 1.0 g kaolin in 100 mL distilled water. The
two titrametric methods.
pH value should be between 4.5 and 6.0 after 5 min.
5. Significance and Use
6.2.3.2 A mixture of 2.0 g kaolin and 200 mL distilled water
are shaken for 10 min and the mixture filtered through the
5.1 This test method is used to determine one of the
standard filter paper (see 6.5). A 100 mL aliquot of the clear
chemical properties of tannery liquors which are relevant for
filtrate should have less than 0.001 g of residue after evapora-
the vegetable tanning process and influence the astringency of
tion and oven-drying in a platinum dish.
vegetable tanning liquors. The astringency of liquors is depen-
6.2.4 Alkaline Titrant, 0.1 N sodium hydroxide solution.
dent upon the solids and tannin content and the acidity. This
6.3 Acidity Determination—Method II:
6.3.1 Pipet, transfer pipette with 6 mL capacity.
This test method is under the jurisdiction of ASTM Committee D-31 on Leather
6.3.2 pH Meter, with glass/calomel electrodes.
and is the direct responsibility of Subcommittee D31.01 on Vegetable Leather. This
6.3.3 Alkaline Titrant, 0.1 N sodium hydroxide solution.
test method has been adapted from and is a replacement for the acidity determina-
tion portion of Method A25 of the Official Methods of the American Leather
Chemists Association.
Current edition approved May 10, 1999. Published August 1999. The sole source of supply of Kaolin known to the committee at this time is L.
Annual Book of ASTM Standards, Vol 15.04. H. Lincoln & Son, Inc., 203 Cherry Street, Coudersport, PA 16915. If you are aware
Official Methods of the American Leather Chemists Association. Available of alternative suppliers, please provide this information to ASTM Headquarters.
from the American Leather Chemists Association, University of Cincinnati, P.O. Your comments will receive careful consideration at a meeting of the responsible
Box 210014, Cincinnati, OH 45221-0014. technical committee, which you may attend.
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