ASTM D3897-91(2001)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D3897–91(Reapproved 2001)
Standard Practice for
Calculation of Basicity of Chrome Tanning Liquors
This standard is issued under the fixed designation D 3897; 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 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 D 3898) and the acidity A 2 B
Basicity, % 5 3 100 (1)
determination (Test Method D 3913) can be combined to A
permit 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 D 3898,
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 D 3913.
2. Referenced Documents
2.1 ASTM Standards:
6. Precision and Bias
D 3898 Test Method for Chromic Oxide in Basic Chro-
6.1 Because basicity is in effect a ratio, the precision
mium Tanning Liquors
indexes are transmitted by the laws governing ratios. If the
D 3913 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
E 180 Practice for Determining the Precision of ASTM
example, percent of value being determined, the precision with
Methods for theAnalysis and Testing of Industrial Chemi-
which the basicity is known will be:
cals
2 2
P 5 P 1 P (2)
B = C A
R
3. Significance and Use
where:
3.1 Basicity is a ratio. In any chromic salt solution, the
P = precision of acidity in basic chromium tanning
A
electrovalence of the chromium (+3) is satisfied by the hy-
liquors,
droxyl ions and by acid ions. The extent to which this
P = precision of chromic oxide in basic chromium
C
electravalence is satisfied by the hydroxyl ions, expressed as a R
tanning liquors,
percentage, is the basicity. The basicity of a chrome tanning
P = precision of basicity in basic chromium tanni
...