1、Designation: D 1331 11Standard 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 ye
2、ar 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 These test methods cover the determination of surfacetension and interfacial tension of solutions of surface-act
3、iveagents, as defined in Terminology D 459D459. Two methodsare covered 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.
4、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
5、 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:2
6、D459 Terminology Relating to Soaps and Other Detergents3. 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
7、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 sur
8、face 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 o
9、f 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 th
10、e 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 thedi
11、al 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 s
12、hall 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 thetorsi
13、on 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
14、 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 the1These test methods are under the jurisdiction of A
15、STM Committee D01 onPaint and Related Coatings, Materials, and Applications and are the directresponsibility of Subcommittee D01.24 on Physical Properties of Liquid Paints andPaint Materials.Current edition approved June 1, 2011. Published June 2011. Originallyapproved in 1954. Last previous edition
16、 approved in 2001 as D1331 - 89 (2001)which was withdrawn January 2010 and reinstated in June 2011.2For 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 Doc
17、ument Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.dial-adjusting screw until the index level of the arm is oppositethe reference line of the mirror. Record the dial reading to 0.10division. Call th
18、is “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):gc5 M 3 g!/2L (1)where:M = weight placed on the paper platform, g,g = gravity constant (Note 2), cgs units, andL = mean circumference of the ring (furnishe
19、d by themanufacturer with each ring).If the recorded dial reading “gamma-c” is greater than thecalculated value, the torsion arm should be shortened. If“gamma-c” is less than the calculated value, the torsion armshould be lengthened. Repeat the calibration procedure, read-justing the zero position a
20、fter each change in the length of thetorsion arm, until the dial reading agrees with the calculatedvalue. Each unit of the scale now represents a pull on the ringof 1 dyne/cm. Note that a conversion factor, F (see 5.1.3), mustbe multiplied by the scale reading to give corrected surfacetension in dyn
21、es per centimetre.NOTE 1ExampleIf M is exactly 0.600 g and L is 4.00 cm:gc= (0.600 3 980.3)/(2 3 4.00) = 73.52 dynes/cmNOTE 2The gravity constant is 980.3 at Chicago; in other localities itwill differ very slightly from this value.5.1.3 After the tensiometer has been calibrated, it is conve-nient to
22、 calculate the number of grams total pull on the ring thatis represented by each scale division. This is done simply bydividing the scale reading into the weight used for calibration(Note 3). This value is used in the calculation of the conversionfactor, F, mentioned in 5.1.2.NOTE 3In the example gi
23、ven in Note 1, each scale unit aftercalibration represents:0.600/73.52 5 0.008161 g (2)5.1.4 Interfacial TensiometerWith the interfacial tensiom-eter, the same principle of calibrating by adjusting the length ofthe torsion arm also applies. This instrument has, however, inaddition to the torsion arm
24、, a torsion-arm counterbalance.Adjust the length of this counterbalance to coincide with that ofthe torsion arm itself, in order that the vertical members of theassembly may remain in line.METHOD ASURFACE TENSION6. Procedure6.1 After the tensiometer has been calibrated, check thelevel and insert the
25、 cleaned platinum ring (Note 4) that will beused in the measurement. Check the plane of the ring, and setthe dial and vernier at zero. Adjust the rear adjusting screw sothat the index level of the arm is opposite the reference markon the mirror, that is, the ring system is at the zero position.NOTE
26、4Extreme care must be taken to have the sample vessel andplatinum ring clean. Contamination of the liquid surface by dust or otheratmospheric impurities during measurement should be avoided.6.2 Place the solution to be tested (Note 5), contained in thethoroughly cleaned vessel (Note 4), on the sampl
27、e platform.Raise the sample platform by means of its adjusting screw untilthe ring is just submerged.NOTE 5Since the surface tension of a solution is a function of theconcentration, care must be taken that the concentration is adjusted andrecorded within known limits. The presence of solutes other t
28、han thesurface-active agent should be ascertained and reported qualitatively andquantitatively, insofar as possible. This includes hardness components inthe water. Care should be taken that the solution is physically homoge-neous. Measurements made near or above the cloud point or other criticalsolu
29、bility points can be in serious error. This is particularly true when thesolute is a surface-active material.6.3 Lower the platform slowly, at the same time applyingtorsion to the wire by means of the dial-adjusting screw. Thesesimultaneous adjustments must be carefully proportioned sothat the ring
30、system remains constantly in its zero position. Asthe breaking point is approached, the adjustments must bemade more carefully and more slowly. Record the dial readingwhen the ring detaches from the surface.6.4 Make at least two measurements. Additional measure-ments shall be made if indicated by th
31、e over-all variationobtained, the total number of readings to be determined by themagnitude of that variation.6.5 Record the temperature of the solution and the age of thesurface at the time of testing. Since the submerging of the ring(6.2) may constitute a significant disturbance of the surface,tak
32、e the age as the elapsed time between submersion andbreakaway of the ring. The accuracy of this time observationmay be indicated in the usual manner. In most cases anaccuracy of 65 s is reasonable, and sufficient for this testmethod.7. Calculation and Report7.1 The dial reading, obtained from a meas
33、urement carriedout in the foregoing manner with a calibrated instrument, isactually the pull per linear centimetre on the ring (both innerand outer circumference being considered) at the break-point,expressed in dynes. This value, called the uncorrected surfacetension, must be multiplied by a correc
34、ting factor, F, to give thecorrected surface tension. F is a function of the contours of theliquid surface in the neighborhood of the ring at the instant ofbreakaway. It can be numerically specified in terms of R, themean radius, in centimetres, of the ring; r, the radius, incentimetres, of the wire
35、 from which the ring is made; and V, themaximum volume of liquid elevated above the free surface ofthe liquid. For liquids of low surface tension, such as surface-active agents, F is, in general, appreciably less than unity. Itmust, therefore, be ascertained and applied. Values of F interms of two c
36、ompounded parameters, R3/V and R/r have beencompiled and tabulated by Harkins and Jordan.3In order tolook up F in the tables, the values of these two parameters mustbe calculated. Values for R and r are furnished by themanufacturer with each ring. The value of V is calculated fromthe following equat
37、ion:3Harkins, W. D., and Jordan, H. F., “A Method for Determination of Surface andInterfacial Tension from the Maximum Pull on a Ring,” Journal Am. ChemicalSoc., Vol 52, 1930, p. 1751. These tables are also published in Physical Methodsof Organic Chemistry , Interscience Publishers, Inc., NewYork, N
38、Y, Vol 1, 1945, pp.182184.D1331112V 5 M/D 2 d! (3)where:M = weight of liquid raised above the free surface of theliquid,D = density of liquid, andd = density of air saturated with vapor of the liquid.To calculate M, multiply the tensiometer dial reading by thefactor which converts this reading into
39、grams pull on the ring,as calculated in 5.1.3. The factor D can be measured by theusual procedures, and the value d can be obtained frompublished data. The corrected surface tension in dynes percentimetre is obtained by multiplying the uncorrected surfacetension value by F.7.2 Unless specified, the
40、surface tension values reportedshall be corrected values. Report also the temperature at whichthe measurement was made. If it is desired to report the surfacetension value of an aqueous solution at some standard tem-perature, for example, 25C, and the measurement was actuallymade at a temperature wi
41、thin about 3C of this value (that is,22 to 28C), a correction factor of 0.14 dynes/cmC may beused. Subtract this correction factor from the surface tensionwhen the temperature of the test is lower than the reportedtemperature, and add it to the surface tension when thetemperature of the test is high
42、er than the reported temperature.This value for the correction factor is not valid for nonaqueousliquids, and should be used only where the solvent is prepon-derantly water.METHOD BINTERFACIAL TENSION8. Procedure8.1 Determine interfacial tension as described in Section 6for surface tension, with the
43、 following modifications:8.1.1 Always move the ring from the aqueous side of theinterface through to the nonaqueous side. With liquids lighterthan water, it is accordingly possible to use the precisiontensiometer as well as the interfacial tensiometer. With liquidsheavier than water, where the ring
44、must be pushed downward,the interfacial tensiometer should be used.8.1.2 Use fresh solutions and a freshly cleaned ring for eachdetermination.8.1.3 When operating with a liquid heavier than the aqueoussolution, place the two-layer system in the sample vessel andplace the ring in the upper (aqueous)
45、layer. Make the measure-ment by turning the torsion wire counter-clockwise and simul-taneously keeping the ring system in the zero position, as in themeasurement of surface tension, until the ring breaks throughthe interface.8.1.4 When operating with a liquid (oil) lighter than theaqueous solution,
46、first place the aqueous solution in the samplevessel and immerse the ring therein. Carefully pour the oil ontop of the aqueous solution to form the two-layer system.Contact between the oil and the ring should be avoided duringthis operation. After allowing sufficient time for the interfacialtension
47、to come to its equilibrium value (Note 6), make themeasurement in the same manner as that used for measuringsurface tension.NOTE 6Since the interfacial energy of a newly formed liquid-liquidinterface generally requires some time to reach its equilibrium value, it isadvisable to wait at least 5 min a
48、fter the interface is formed before takinga measurement.9. Calculation and Report9.1 As in the case of surface tension, a correction factor, F,must be multiplied by the dial reading (pull on the ring indynes) in order to obtain the corrected value for interfacialtension. Values for F have been publi
49、shed by Zuidema andWaters.4The factor F is, in this case, a function of the densitiesof the two liquids as well as of R and r, the radius of the ringand that of the wire, respectively.9.2 Unless specified, interfacial tension values reportedshall be corrected values. Report and adequately specify thenature of the nonaqueous liquid (oil) used in the determination.Also report the temperature at which the determination wasmade. In contrast to surface tension values, interfacial tensionvalues cannot adequately be corrected for small temperaturedeviations by means of a
