ASTM D3897-91(2006)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D3897–91(Reapproved 2006)
Standard Practice for
Calculation of Basicity of Chrome Tanning Liquors
This standard is issued under the fixed designation D3897; 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 per cent of the total chromic oxide that is combined with
hydroxyl and is calculated as follows:
1.1 This practice is intended to show how the results of the
chromium analysis (Test Method D3898) and the acidity A 2 B
Basicity, % 5 3 100 (1)
determination(TestMethodD3913)canbecombinedtopermit A
calculation of the basicity of a chrome tanning liquor.
where:
1.2 This standard does not purport to address all of the
A = the amount of thiosulfate, as mL of 0.1 N solution
safety concerns, if any, associated with its use. It is the
required to titrate the 25 mLaliquot as the specimen in
responsibility of the user of this standard to establish appro-
Test Method D3898,
priate safety and health practices and determine the applica-
B = the amount of sodium hydroxide, as mL of 0.1 N
bility of regulatory limitations prior to use.
solution required to titrate the 25 mL aliquot of the
specimen in Test Method D3913.
2. Referenced Documents
2.1 ASTM Standards:
6. Precision and Bias
D3898 Test Method for Chromic Oxide in Basic Chromium
6.1 Because basicity is in effect a ratio, the precision
Tanning Liquors
indexes are transmitted by the laws governing ratios. If the
D3913 Test Method for Acidity in Basic Chromium Tan-
precision of accuracy of the chromic oxide determination or of
ning Liquors
the titratable acidity is expressed in the same relative units; for
example, percent of value being determined, the precision with
3. Significance and Use
which the basicity is known will be:
3.1 Basicity is a ratio. In any chromic salt solution, the
2 2
electrovalence of the chromium (+3) is satisfied by the hy- P 5 P 1 P (2)
B = C A
R
droxyl ions and by acid ions. The extent to which this
where:
electravalence is satisfied by the hydroxyl ions, expressed as a
P = precision of acidity in basic chromium tanning
A
percentage, is the basicity. The basicity of a chrome tanning
liquors,
liquid is closely related to the tanning behavior of the solution.
P = precision of chromic oxide in basic chromium
C
R
4. Procedure tanning liquors,
P = precision of basicity in basic chromium tanning
B
4.1 Determine the chromic oxide as described in Test
liquors.
Method D3898. Determine the acid as described in Test
6.2 For the re
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