ASTM_D_1331_-_89_2001.pdf

Designation:D 1331 89(Reapproved 2001)Standard Test Methods forSurface and Interfacial Tension of Solutions of Surface-Active Agents1This standard is issued under the fixed designation D 1331;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 These test methods cover the determination of surfacetension and interfacial tension of solutions of surface-activeagents,as defined in Terminology D 459.Two methods arecovered as follows:Method ASurface Tension.Method BInterfacial Tension.1.2 Method A is written primarily to cover aqueous solu-tions of surface-active agents,but is also applicable to non-aqueous solutions and mixed solvent solutions.1.3 Method B is applicable to two-phase solutions.Morethan one solute component may be present,including solutecomponents that are not in themselves surface-active.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 practices and determine the applica-bility of regulatory limitations prior to use.Material SafetyData Sheets are available for reagents and materials.Reviewthem for hazards prior to usage.2.Referenced Documents2.1 ASTM Standards:D 459 Terminology Relating to Soaps and Other Deter-gents23.Apparatus3.1 TensiometerEither the du Nouy precision tensiometeror the du Nouy interfacial tensiometer,equipped with either the4 or the 6-cm circumference platinum ring,as furnished by themanufacturer,may be used.The tensiometer shall be placed ona sturdy support that is free from vibrations and other distur-bances such as wind,sunlight,and heat.The wire of the ringshall be in one plane,free of bends or irregularities,andcircular.When set in the instrument,the plane of the ring shallbe horizontal,that is,parallel to the surface plane of the liquidbeing tested.3.2 Sample ContainerThe vessel for holding the liquidshall be not less than 6 cm in diameter,and sufficiently large toensure that the contact angle between the ring and the interfaceis zero.4.Preparation of Apparatus4.1 Clean all glassware thoroughly.The use of freshchromic-sulfuric acid cleaning mixture,followed by a thor-ough rinsing in distilled water,is recommended.4.2 Clean the platinum ring by rinsing thoroughly in asuitable solvent and in distilled water,before taking a set ofmeasurements.Allow the ring to dry,and then heat to whiteheat in the oxidizing portion of a gas flame.5.Calibration of Apparatus5.1 The tensiometer is,in fact,a torsion balance,and theabsolute accuracy depends on the length of the torsion arm,which is adjustable.Torsion may be applied to the wire bymeans of either the dial-adjusting screw(which controls thedial reading)or a rear adjusting screw.Calibration consistsessentially in adjusting the length of the torsion arm so that thedial scale will read directly in dynes per centimetre.Theprecision tensiometer shall be calibrated in accordance with thefollowing:5.1.1-5.1.3;the interfacial tensiometer shall becalibrated in accordance with 5.1.1-5.1.4.5.1.1 Level the tensiometer.A liquid level of the typeemployed on analytical balances may be used.Place the levelon the table that holds the sample for testing,and adjust the legscrews of the tensiometer until the table is horizontal.Pull thetorsion wire taut by means of the tension screw,and adjust thedial reading and the vernier to zero.Insert the platinum ring inthe holder,and place a small piece of paper across the ring.This will serve as a platform to hold the calibrating weight.Turn the rear adjusting screw of the torsion wire until the indexlevel of the arm is opposite the reference line of the mirror;thisautomatically compensates for the weight of the paper plat-form.Next,place an accurately standardized weight of be-tween 500 and 800 mg on the paper platform and turn thedial-adjusting screw until the index level of the arm is oppositethe reference line of the mirror.Record the dial reading to 0.10divison.Call this“gamma-c.”5.1.2 Calculate what the reading“gamma-c”obtained in5.1.1 should be when the tensiometer is properly adjusted,asfollows(Note 1):gc5M 3 g!/2L(1)1These test methods are under the jurisdiction of ASTM Committee D12 onSoaps and Other Detergents and are the direct responsibility of SubcommitteeD12.15 on Physical Testing.Current edition approved May 26,1989.Published July 1989.Originallypublished as D 1331 54 T.Last previous editions D 1331 56(1986).2Annual Book of ASTM Standards,Vol 15.04.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.where:M=weight placed on the paper platform,g,g=gravity constant(Note 2),cgs units,andL=mean circumference of the ring(furnished by themanufacturer with each ring).If th