ASTM_D_3875_-_15.pdf

Designation:D387515Standard Test Method forAlkalinity in Brackish Water,Seawater,and Brines1This standard is issued under the fixed designation D3875;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.1.Scope*1.1 This test method covers the determination of alkalinityin brackish water,seawater,and brines.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.2.Referenced Documents2.1 ASTM Standards:D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE200 Practice for Preparation,Standardization,and Storageof Standard and Reagent Solutions for Chemical Analysis3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,refer to Terminology D1129.4.Summary of Test Method4.1 An electrotitrator or pH meter is used to determine theamount of acid necessary to reach pH 8.1 and 4.5,respectively.The pH values approximate the points where the hydroxide andbicarbonate ions are neutralized.5.Significance and Use5.1 Alkalinity as carbonate and bicarbonate of saline wateris very important in chemical waterflooding or tertiary recov-ery processes for recovering petroleum.Alkaline waters offerbetter wetting to the formation rock and improve oil release.Asan additional benefit,ions that provide alkalinity adsorb onrock surfaces occupying adsorption sites and decrease the lossof recovery chemical by adsorption.Determination of alkalin-ity in waters used in tertiary recovery processes is thereforevery important.5.2 An alkalinity value is necessary in the calculation ofcarbonate scaling tendencies of saline waters.It is also neces-sary to determine the alkalinity if the ionic balance of a wateranalysis is to be used as a check of the reliability of theanalysis.6.Interferences6.1 Anions other than bicarbonate,carbonate,or hydroxideions that form weakly dissociated acids that participate inhydrolysis reactions may also contribute to the alkalinity asmay some organic materials.The user of this test method ondetermining the alkalinity is cautioned that all the effects of theanions entering into hydrolysis reactions are combined andreported as an equivalent amount of a single substance or twopostulated ions.Included in the reported value is the alkalinityresulting from the presence of borate,silicate,sulfide,andphosphate.The effect of borate on the alkalinity value isconsidered negligible for waters with pH values of 7 or less.7.Apparatus7.1 Electrotitrator or Standard pH Meter with suitableelectrodes.Maintenance and standardization of electrodes andpH meter should follow manufacturers instructions becauseperformance can be affected by improper treatment.NOTE1Automatic titrators with combined pH electrode are found1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Feb.1,2015.Published April 2015.Originallyapproved in 1980.Last previous edition approved in 2008 as D3875 08.DOI:10.1520/D3875-15.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 useful to increase reliability and save time.The use of an automatic titratoris recommended in the procedure.7.2 Buret,10-mL micro.8.Reagents8.1 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 onAnalytical Reagents of theAmerican Chemical Society,2where such specifications are available.Other 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.8.2 Purity of WaterUnless otherwise indicated,referenceto water shall be understood to mean reagent water conformingto Specification D1193,Type I.Other reagent water types maybe used provided it is first ascertained that the water is ofsufficiently high purity to permit its use without adverselyaffecting the bias and precision of this test method.Type IIwater was specified at the