ASTM_D_516_-_11.pdf

Designation:D51611Standard Test Method forSulfate Ion in Water1This standard is issued under the fixed designation D516;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 Department of Defense.1.Scope*1.1 This turbidimetric test method covers the determinationof sulfate in water in the range from 5 to 40 mg/L of sulfate ion(SO4).1.2 This test method was used successfully with drinking,ground,and surface waters.It is the users responsibility toensure the validity of this test method for waters of untestedmatrices.1.3 Former gravimetric and volumetric test methods havebeen discontinued.Refer to Appendix X1 for historical infor-mation.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 This standard does not purport to address the safetyconcerns,if any,associated with its use.It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1066 Practice for Sampling SteamD1129 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 AnalysisE60 Practice for Analysis of Metals,Ores,and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3.Terminology3.1 Definitions For definitions of terms used in this testmethod,refer to Terminology D1129.4.Summary of Test Method4.1 Sulfate ion is converted to a barium sulfate suspensionunder controlled conditions.Asolution containing glycerin andsodium chloride is added to stabilize the suspension andminimize interferences.The resulting turbidity is determinedby a nephelometer,spectrophotometer,or photoelectric colo-rimeter and compared to a curve prepared from standard sulfatesolutions.5.Significance and Use5.1 The determination of sulfate is important because it hasbeen reported that when this ion is present in excess of about250 mg/L in drinking water,it causes a cathartic action(especially in children)in the presence of sodium and magne-sium,and gives a bad taste to the water.6.Interferences6.1 Insoluble suspended matter in the sample must beremoved.Dark colors that cannot be compensated for in theprocedure interfere with the measurement of suspended bariumsulfate(BaSO4).6.2 Polyphosphates as low as 1 mg/L will inhibit bariumsulfate precipitation causing a negative interference.Phospho-nates present in low concentrations,depending on the type ofphosphonate,will also cause a negative interference.Silica inexcess of 500 mg/L may precipitate along with the bariumsulfate causing a positive interference.Chloride in excess of5000 mg/L will cause a negative interference.Aluminum,polymers,and large quantities of organic material present inthe test sample may cause the barium sulfate to precipitatenonuniformly.In the presence of organic matter certain bacte-ria may reduce sulfate to sulfide.To minimize the action ofsulfate reducing bacteria,samples should be refrigerated at 4Cwhen the presence of such bacteria is suspected.1This 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 Sept.1,2011.Published September 2011.Originallyapproved in 1938.Last previous edition approved in 2007 as D516 07.DOI:10.1520/D0516-11.2For 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.*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 6.3 Although other ions normally found in water do notappear to interfere,the formation of the barium sulfate suspen-sion is very critical.Determinations that are in doubt may bechecked by a gravimetric method in some cases,or by theprocedure suggested in Note 2.7.Apparatus7.1 PhotometerOne of the following which are given inorder of preference.7.1.1 Nephelometer or turbidimeter;7.1.2 Spectrophotometer for use at 420 nm with light path of4 to 5 cm;7.1.3 Filter photometer with a violet filter having a maxi-mum near 420 nm and a light path of 4 to 5 cm.7.2 Stopwatch,if the magnetic stir