ASTM_D_1172_-_15.pdf

Designation:D117215Standard Guide forpH of Aqueous Solutions of Soaps and Detergents1This standard is issued under the fixed designation D1172;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()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This guide covers the preparation of aqueous solutionsof soaps and detergents and the determination of their pH.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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:2D460 Test Methods for Sampling and Chemical Analysis ofSoaps and Soap ProductsD501 Test Methods of Sampling and Chemical Analysis ofAlkaline DetergentsE70 Test Method for pH of Aqueous Solutions With theGlass Electrode3.Sampling3.1 The material shall be sampled in accordance with TestMethods D460 or D501,whichever is applicable.4.Reagent4.1 Distilled Water or EquivalentDistilled water orequivalent shall be boiled thoroughly,or purged with CO2-freeair,to remove CO2and shall be protected with soda-lime whilecooling and in storage.The pH of this water shall be between6.2 and 7.2 at 25C.The residue on evaporation,when heatedat 105C for 1 h,shall not be more than 0.5 mg/L.5.Procedure for Synthetic Detergents5.1 Preparation of SolutionsWeigh 1 6 0.001 g of thesample(see Note 1 and Note 2)and transfer to a 1-Lvolumetric flask.Partially fill the flask with distilled water orequivalent and agitate until the sample is completely dissolved.Make certain the solute is completely dissolved and allow timefor the evolution of dissolved gases.Fill to the calibration markwith distilled water or equivalent.Stopper the flask;mixthoroughly.The desirable condition requires the solution tocome to equilibrium.Allow the solution to equilibrate at 25 62.0C.The use of a temperature compensation probe mayallow alternate temperatures.Records should show the timeinterval between solution preparation and pH measurement.NOTE1The procedure for detergents other than soaps is applicable tosome compositions that contain minor proportions of soap,provided thatthe solutions do not show evidence of gelling prior to carrying out the pHmeasurement.NOTE2Measurements of pH of gelled solutions lack constancy andreproducibility.The procedure for soaps(Section 6)is designed to producesolutions that will not gel before the pH measurement is carried out.Thisprocedure should be used for all detergent solutions,soap or nonsoap,thatgive evidence of gelling or incomplete solution when prepared inaccordance with 5.1.The procedure for soaps is not applicable to detergentcompositions that are known to be chemically altered by the boiling waterused in dissolving the sample,or that are intended exclusively for use incold water.5.2 Determination of pHCalibrate the pH meter andsuitable electrodes.The recommended electrodes are FisherScientific accupHast Variable Temperature pH CombinationElectrodes or Orion Ross Sure Flow electrode or equivalentelectrodes.Measure the pH of the solution while stirring.6.Procedure for Soaps(use for soaps and detergents thattend to gel when added to water at room temperature)6.1 Preparation of ApparatusUse a pH meter and elec-trodes as defined in Test Method E70.Set the temperaturecontrol knob at 40C and standardize the assembly with asuitable buffer solution in the pH 9 to 11 range at 40C.Leavethe electrode in the buffer to maintain temperature equilibrium.Have the apparatus ready for immediate use.1This guide is under the jurisdiction of ASTM Committee D12 on Soaps andOther Detergents and is the direct responsibility of Subcommittee D12.15 onPhysical Testing.Current edition approved May 1,2015.Published July 2015.Originally approvedin 1951.Last previous edition approved in 2007 as D1172 95(2007).DOI:10.1520/D1172-15.2For 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 website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2 Preparation of SolutionWeigh 0.30 6 0.01 g of thesample(see Note 2)and transfer to a 250-mLErlenmeyer flask.Add 100 mL of boiling distilled water or equivalent that hasbeen boiled vigorously for 15 min jus