ASTM D2448-85(2019)

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.
Designation: D2448 −85 (Reapproved 2019)
Standard Test Method for
Water-Soluble Salts in Pigments by Measuring the Specific
Resistance of the Leachate of the Pigment
This standard is issued under the fixed designation D2448; 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 3. Summary of Test Method
1.1 Thistestmethodcoversthedeterminationofthespecific
3.1 A weighed quantity of pigment is added to water and
resistance of the aqueous leachate from a pigment as an index
boiled. For hydrophobic pigments methyl alcohol is used to
of water-soluble salt content. This test method is applicable to
facilitate wetting. After filtration, the specific resistance of the
white pigments and colored pigments (organic and inorganic).
filtrate is determined using a conductivity bridge.
The water-soluble salts content is a function of the specific
resistance of the solution formed by extracting the pigment
4. Significance and Use
with water.
4.1 This test method provides a reliable means for the
1.2 This test method is based on a water to pigment ratio of
determination of the relative amounts of these salts when
9+1. The leachate yield (minimum 160 mL) sufficient for
comparing different lots of the same pigment grade. Water-
rinsing the cylinder dip cell and thermometer plus the mini-
soluble salts also affect the water resistance and blister resis-
mum 80 mL required for the measurement to determine the
tance of coatings, especially primers for steel. Conductivity
quantity of pigment to be used.
measurements, however, cannot be used as the only method to
determine and compare the amount of water soluble salts of
1.3 The values stated in SI units are to be regarded as
pigments with the same chemical composition but produced by
standard. No other units of measurement are included in this
different manufacturing processes.
standard.
1.4 This standard does not purport to address all of the
5. Apparatus
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5.1 Centrifuge (optional), having a 500-mL capacity per
priate safety, health, and environmental practices and deter-
cup.
mine the applicability of regulatory limitations prior to use.
5.2 Filter Paper (Note 1)—For high reliability avoid use of
1.5 This international standard was developed in accor-
filter paper containing soluble material. Each filter should be
dance with internationally recognized principles on standard-
washed with reagent water in the funnel until resistance of the
ization established in the Decision on Principles for the
filtrate is greater than 200 000Ω · cm.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical NOTE 1—The size of the filter paper will be determined by how
voluminous the pigment is. Some organic pigments require at least a
Barriers to Trade (TBT) Committee.
185-mm paper for proper filtering.
2. Referenced Documents
5.3 Filter Aid (optional)—The use of a filter aid may be
desirable with some pigments to improve filtration. However,
2.1 ASTM Standards:
the filter aid must be treated to meet the same specifications for
D1193 Specification for Reagent Water
filter paper as given in 5.2.
5.4 Ungraduated Cylinders, approximately 35 mm wide by
This test method is under the jurisdiction of ASTM Committee D01 on Paint 125 mm deep.
and Related Coatings, Materials, andApplications and is the direct responsibility of
5.5 Thermometer, graduated in 0.2°C intervals.
Subcommittee D01.31 on Pigment Specifications.
Current edition approved Oct. 1, 2019. Published October 2019. Originally
5.6 Conductivity Bridge.
approved in 1966. Last previous edition approved in 2012 as D2448 – 85 (2012).
DOI: 10.1520/D2448-85R19.
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 Any commercially produced conductivity bridge and conductivity cell is
the ASTM website. satisfactory.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2448 − 85 (2019)
5.7 Conductivity Cell, having a cell constant, K,of1.The 6.4 Potassium Chloride, Standard Solution (0.02 N)—
cell constant recommended for various ranges of electrolytes is Prepare a 0.02 N potassium chloride (KCl) solution with water
as follows: by dissolving 1.491 g of KCl (heated before weighing for 1 h
5.7.1 For specific resistances of less than 250Ω · cm, use a at 105°C) in water, followed by dilution to 1 L.
cell with a constant of 10 or more.
7. Determination of Cell Constant
5.7.2 For specific resistances from 250 to 200 000Ω · cm,
7.1 Prepare a 0.002 N solution of KCl by diluting the 0.02
use a cell with a constant of 1. This covers the range for most
N KCl solution described in 6.4 with water. Cool and measure
pigments.
the specific resistance, R ,at25 60.5°C as described in 8.2.2.
5.7.3 For specific resistances of reagent water or of over m
200 000Ω · cm, use a cell with a constant of 0.1.
7.2 Calculate the cell constant, K, as follows:
K 5 R /R
~ !
25 m s
6. Reagents
where:
6.1 Purity of Reagents—Reagent grade chemicals shall be
R = specific resistance at 25°C (see 8.2.2), and
used in all tests. Unless otherwise indicated, it is intended that
m
R = specific resistance in ohm centimetres of an 0.002 N
all reagents shall conform to the specifications of the Commit-
s
KCl solution at 25°C (Table 1) = 3427Ω · cm.
tee onAnalytical Reagents of theAmerican Chemical Society,
where such specifications are available. Other grades may be
NOTE 2—In general the “cell constant” is not greatly affected by
used, provided it is first ascertained that the reagent is of variations in the strength of the KCl solution, but for
...