1、Designation: D2448 85 (Reapproved 2012)Standard Test Method forWater-Soluble Salts in Pigments by Measuring the SpecificResistance of the Leachate of the Pigment1This standard is issued under the fixed designation D2448; the number immediately following the designation indicates the year oforiginal
2、adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the specificresistance
3、of the aqueous leachate from a pigment as an indexof water-soluble salt content. This test method is applicable towhite pigments and colored pigments (organic and inorganic).The water-soluble salts content is a function of the specificresistance of the solution formed by extracting the pigmentwith w
4、ater.1.2 This test method is based on a water to pigment ratio of9+1. The leachate yield (minimum 160 mL) sufficient forrinsing the cylinder dip cell and thermometer plus the mini-mum 80 mL required for the measurement to determine thequantity of pigment to be used.1.3 The values stated in SI units
5、are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practic
6、es and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent Water3. Summary of Test Method3.1 A weighed quantity of pigment is added to water andboiled. For hydrophobic pigments methyl alcohol is used tofacilit
7、ate wetting. After filtration, the specific resistance of thefiltrate is determined using a conductivity bridge.4. Significance and Use4.1 This test method provides a reliable means for thedetermination of the relative amounts of these salts whencomparing different lots of the same pigment grade. Wa
8、ter-soluble salts also affect the water resistance and blister resis-tance of coatings, especially primers for steel. Conductivitymeasurements, however, cannot be used as the only method todetermine and compare the amount of water soluble salts ofpigments with the same chemical composition but produ
9、ced bydifferent manufacturing processes.5. Apparatus5.1 Centrifuge (optional), having a 500-mL capacity percup.5.2 Filter Paper (Note 1)For high reliability avoid use offilter paper containing soluble material. Each filter should bewashed with reagent water in the funnel until resistance of thefiltr
10、ate is greater than 200 000 cm.NOTE 1The size of the filter paper will be determined by howvoluminous the pigment is. Some organic pigments require at least a185-mm paper for proper filtering.5.3 Filter Aid (optional)The use of a filter aid may bedesirable with some pigments to improve filtration. H
11、owever,the filter aid must be treated to meet the same specifications forfilter paper as given in 5.2.5.4 Ungraduated Cylinders, approximately 35 mm wide by125 mm deep.5.5 Thermometer, graduated in 0.2C intervals.5.6 Conductivity Bridge.35.7 Conductivity Cell,3having a cell constant, K,of1.Thecell c
12、onstant recommended for various ranges of electrolytes isas follows:5.7.1 For specific resistances of less than 250 cm, use acell with a constant of 10 or more.5.7.2 For specific resistances from 250 to 200 000 cm,use a cell with a constant of 1. This covers the range for mostpigments.1This test met
13、hod is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.31 on Pigment Specifications.Current edition approved Nov. 1, 2012. Published November 2012. Originallyapproved in 1966. Last previous edi
14、tion approved in 2007 as D2448 85 (2007).DOI: 10.1520/D2448-85R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM web
15、site.3Any commercially produced conductivity bridge and conductivity cell issatisfactory.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.7.3 For specific resistances of reagent water or of over200 000 cm, use a cell with a constant
16、of 0.1.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available
17、.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent grade water asdefined
18、by Type II of Specification D1193.6.3 Methanol.6.4 Potassium Chloride, Standard Solution (0.02 N) Pre-pare a 0.02 N potassium chloride (KCl) solution with water bydissolving 1.491 g of KCl (heated before weighing for1hat105C) in water, followed by dilution to 1 L.7. Determination of Cell Constant7.1
19、 Prepare a 0.002 N solution of KCl by diluting the 0.02N KCl solution described in 6.4 with water. Cool and measurethe specific resistance, Rm,at2560.5C as described in 8.2.2.7.2 Calculate the cell constant, K, as follows:K255 Rm/Rs!where:Rm= specific resistance at 25C (see 8.2.2), andRs= specific r
20、esistance in ohm centimetres of an 0.002 NKCl solution at 25C (Table 1) = 3427 cm.NOTE 2In general the “cell constant” is not greatly affected byvariations in the strength of the KCl solution, but for greatest accuracy,measurements should be made at or near the specific resistance of thesolution to
21、be measured and at values that utilize the medium range of thescale of the conductivity bridge, using the same multiplier tap.7.3 The specific resistances of KCl solutions are shown forconcentrations from 0.001 N to 0.073 N at 25 C in Fig. 1. Thiscurve, almost a straight line, was made from publishe
22、d valuesof specific conductances and equivalent conductances of KClsolutions at 25 C. Table 1 gives values of the specificresistances of KCl solutions for those concentrations useful forpigment testing.8. Procedure8.1 Hydrophobicity TestTest a small amount of pigmentwith boiling water to see if it i
23、s water-wettable. Pigments thatdo not wet well with water are probably hydrophobic andshould be treated as described in 8.3. If the pigment wetseasily, proceed as described in 8.2.8.2 Hydrophilic Pigments:8.2.1 A 20.0-g specimen weight is usually sufficient forpigments easily wet with water. Add 20.
24、0 g of the pigment to180 g of boiling water in a tared, 400-mL beaker with stirringrod. (Usually a 250-mL beaker is sufficient for white pigments.Some white pigment, because of tendency to foam and crawl,4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washingt
25、on, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Specif
26、ic Resistance of Potassium Chloride at 25CD2448 85 (2012)2can be handled better in a larger beaker. Usually 20-g speci-mens of organic pigments require a 600-mL beaker to allowadequate room for foaming. Boil slowly for 5 min withoccasional stirring. Cool to about 60C and add water to bringthe net we
27、ight back to 200 g. Stir thoroughly. Filter directlythrough fine-texture paper (Note 1) or separate the solids bycentrifuge using clean, dry cups, or cups washed with some ofthe slurry, followed by decanting the supernatant liquidthrough a filter. In either case discard the first 10 mL throughthe fi
28、lter.8.2.2 Cool the filtrate to about 20C. Rinse the footedcylinder and the conductivity cell, previously rinsed withwater, with the leachate. Fill the footed cylinder with theleachate to be measured and place the conductivity cell into theleachate. Move the dip cell up and down to remove all airbub
29、bles. Adjust the temperature slowly to 25C and, with thecell submerged so that the vent is12 in. (12.7 mm) below thesurface of the liquid and centered upright in the cylinder, makeat least five measurements of the specific resistance at 25 60.5C, using the conductivity bridge with the multiplier set
30、 togive a reading near the center of the scale, following theinstructions supplied with the instrument to obtain a balance.8.3 Hydrophobic PigmentsA modification of the proce-dure given in 8.2 is necessary for organic pigments that are noteasily wet with water. Wet 30.0 g of pigment with 5 to 20 g o
31、falcohol, as required, to produce a smooth wet paste. Completethe addition of water to bring the net weight to 300 g bydiluting with boiling water in a tared beaker (1000 mL has beenfound satisfactory), with a stirring rod. Boil, cool, filter, anddetermine the reading as outlined in 8.2.2.9. Calcula
32、tion9.1 Calculate the specific resistance, R25,inohmcentimetres, of the pigment at 25C by taking the mean Ra,ofthe five or more readings made and divide by the cell constant,K, determined in accordance with Section 7.10. Precision and Bias10.1 On the basis of a laboratory study of this test method,t
33、he following criteria should be used for judging the accept-ability of results at the 95 % confidence level:10.1.1 RepeatabilityTwo results obtained by the sameoperator should be considered suspect if they differ by morethan 5 % for white pigments and 7 % for colored organicpigments.10.1.2 Reproduci
34、bilityTwo results obtained by operatorsin different laboratories should be considered suspect if theydiffer by more than 10 % for white pigments and 15 % forcolored organic pigments.10.2 BiasBias has not been determined for this testmethod.11. Keywords11.1 inorganic pigments; leachate; organic pigme
35、nts; watersoluble salts; white pigmentsASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the
36、riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of
37、this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldma
38、ke your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained
39、by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).TABLE 1 Specific Resistances of Solutions of PotassiumChloride at 25CNormality cm0.001 6802 (1)0.002 3427 (1)0.005 1393 (1)0.01 707.3 (1,2)0.02 361.5 (3)D2448 85 (2012)3
