Standard Test Method for Determination of Water …

1 Designation: D 6304 07An American National StandardStandard Test Method forDetermination of Water in Petroleum Products, LubricatingOils, and Additives by Coulometric Karl Fischer Titration1 This Standard is issued under the fixed designation D 6304; 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 Scope* This test Method covers the direct Determination ofwater in the range of 10 to 25 000 mg/kg entrained Water inpetroleum products and hydrocarbons using automated instru-mentation.

2 This test Method also covers the indirect analysis ofwater thermally removed from samples and swept with dryinert gas into the Karl Fischer titration cell. Mercaptan, sulfide(S or H2S), sulfur, and other compounds are known tointerfere with this test Method (see Section5). This test Method is intended for use with commerciallyavailable coulometric Karl Fischer reagents and for the deter-mination of Water in additives, lube oils, base oils, automatictransmission fluids, hydrocarbon solvents, and other petroleumproducts. By proper choice of the sample size, this test methodmay be used for the Determination of Water from mg/kg topercent level The values stated in SI units are to be regarded asstandard.

3 No other units of measurement are included in 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 Referenced standards :2D 1193 Specification for Reagent WaterD 1298 Test Method for Density, Relative Density (SpecificGravity), or API Gravity of Crude Petroleum and LiquidPetroleum Products by Hydrometer MethodD 4052 Test Method for Density and Relative Density ofLiquids by Digital Density MeterD 4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD 4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD 5854 Practice for Mixing and Handling of LiquidSamples of Petroleum and Petroleum ProductsE 203 Test Method for Water Using Volumetric Karl FischerTitration3.

4 Summary of Test An aliquot is injected into the titration vessel of acoulometric Karl Fischer apparatus in which iodine for the KarlFisher reaction is generated coulometrically at the all of the Water has been titrated, excess iodine isdetected by an electrometric end point detector and the titrationis terminated. Based on the stoichiometry of the reaction, 1 molof iodine reacts with 1 mol of Water ; thus, the quantity of wateris proportional to the total integrated current according toFaraday s The sample injection can be done either by mass The viscous samples can be analyzed by using a watervaporizer accessory that heats the sample in the evaporationchamber, and the vaporized Water is carried into the KarlFischer titration cell by a dry inert carrier Significance and A knowledge of the Water content of lubricating oils,additives, and similar products is important in the manufactur-ing, purchase, sale.

5 Or transfer of such petroleum products tohelp in predicting their quality and performance For lubricating oils, the presence of moisture could leadto premature corrosion and wear, an increase in the debris loadresulting in diminished lubrication and premature plugging offilters, an impedance in the effect of additives, and undesirablesupport of deleterious bacterial A number of substances and classes of compoundsassociated with condensation or oxidation-reduction reactionsinterferes in the Determination of Water by Karl Fischer1 This test Method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of on Sampling, Sediment, edition approved July 15, 2007.

6 Published August 2007. Originallyapproved in 1998. Last previous edition approved in 2004 as D 6304 referenced ASTM standards , visit the ASTM website, , orcontact ASTM Customer Service at ForAnnual Book of ASTMS tandardsvolume information, refer to the Standard s Document Summary page onthe ASTM *A Summary of Changes section appears at the end of this ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United In petroleum products, the most common interfer-ences are mercaptans and sulfides. At levels of less than500 mg/kg as sulfur, the interference from these compounds isinsignificant for Water concentrations greater than %.

7 For more information on substances that interfere inthe Determination of Water by the Karl Fischer titration Method ,see Test MethodE 203. Some interferences, such as ketones,may be overcome if the appropriate reagents are The significance of the mercaptan and sulfide interfer-ence on the Karl Fischer titration for Water in the 10 to 200mg/kg range has not been determined experimentally. At theselow Water concentrations, however, the interference may beexpected to be significant for mercaptan and sulfide concen-trations of greater than 500 mg/kg as Helpful hints in obtaining reliable results are given inAppendix Karl Fischer Apparatus (using electromet-ric end point) A number of automatic coulometric KarlFischer titration assemblies consisting of titration cell, plati-num electrodes, magnetic stirrer, and a control unit are avail-able on the market.

8 Instructions for operation of these devicesare provided by the manufacturers and are not Vaporizer Accessory A number of automaticwater vaporizer accessories are available on the for the operation of these devices are provided bythe manufacturers and are not described Samples are most easily added to the titrationvessel by means of accurate glass or disposable plastic syringeswith luer fittings and hypodermic needles of suitable length todip below the surface of the anode solution in the cell wheninserted through the inlet port septum. The bores of the needlesused shall be kept as small as possible, but large enough toavoid problems arising from back pressure or blocking whilesampling.

9 Suggested syringe sizes are as Ten microlitres, with a needle long enough to dipbelow the surface of the anode solution in the cell wheninserted through the inlet port septum and graduated forreadings to the nearest L or better. This syringe can beused to accurately inject a small quantity of Water to checkreagent performance as described in As identified inTable 1, syringes of the followingcapacities: 250 L accurate to the nearest 10 L; 500 Laccurate to the nearest 10 L; 1 mL accurate to the mL; 2 mL accurate to the nearest mL; and 3 mLaccurate to the nearest mL.

10 A quality gas-tight glasssyringe with a TFE-fluorocarbon plunger and luer fitting Reagents and of Reagents Reagent grade chemicals shall beused in all tests . Unless otherwise indicated, all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society3, where suchspecifications are available. Use other grades, provided thereagent is of sufficiently high purity to permit its use withoutlessening the accuracy of the of Water Unless otherwise indicated, referencesto Water shall be understood to mean reagent Water as definedby Type II of SpecificationD , Reagent Grade, less than 100 to 200 mg/kgwater, dried over a molecular sieve (Warning harmful).