ASTM_D_6714_-_16.pdf

Designation:D671416Standard Test Method forChromic Oxide in Ashed Wet Blue(Perchloric AcidOxidation)1This standard is issued under the fixed designation D6714;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.Scope1.1 This test method covers the determination of chromicoxide in Wet Blue that has been partly or completely tannedwith chromium compounds.In general the samples will con-tain chromium content between 1 and 5%,calculated aschromic oxide expressed upon a dry basis otherwise referred toas moisture-free basis(mfb).1.2 This test method is specific in that it applies to a sampleor samples that are the resultant ash following the execution ofTest Method D6716.1.3 This test method does not apply to Wet White.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 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.Specific hazards aregiven in Section 8.2.Referenced Documents2.1 ASTM Standards:2D6658 Test Method for Volatile Matter(Moisture)of WetBlue by Oven DryingD6659 Practice for Sampling and Preparation of Wet Blueand Wet White for Physical and Chemical TestsD6716 Test Method for Total Ash in Wet Blue or Wet WhiteE180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial and Spe-cialty Chemicals(Withdrawn 2009)33.Terminology3.1 DefinitionsThe terms and definitions employed withinthis test method are commonly used in normal laboratorypractice and require no special comment.4.Summary of Test Method4.1 The perchloric acid method may be applied to the ashobtained in Test Method D6716.The resultant ash is dissolvedinto acidic solution in a blend of nitric acid and a preparedoxidation mixture consisting of sulfuric and perchloric acids.Once completed,oxidation of all trivalent to hexavalentchromium is executed by controlled heating.Upon dilution,thechromium is indirectly(back)titrated volumetrically withstandardized thiosulfate using released iodine as the titrate.Theperchloric acid method requires less manipulation than proce-dures based on fusion of the ash.However care must be takenbecause of potential hazards in the use of perchloric acid.Theperchloric acid method also tends to give low results.5.Significance and Use5.1 The procedure described is specific for chromium in WetBlue.Vanadium is the only common interfering element andthis is rarely present in quantity.The precision and accuracy ofthe methods are usually at least as good as the sampling of theWet Blue itself,and the accuracy of previously performed testmethods.5.2 The chromium content of Wet Blue is related to thedegree of tannage obtained,and hence may be a matter forspecification in the purchase of Wet Blue.The proceduredescribed provides adequate accuracy for this purpose.6.Apparatus6.1 Analytical Balance,accurate and calibrated to 0.001 g.6.2 Erlenmeyer Flasks,250 mL capacity or equivalent.6.3 Burette,50 mL capacity of suitable calibration grade,minimum calibration of 0.1 mL.6.4 Glass Anti-bumping Beads,or equivalent.6.5 Measuring Cylinders,50 mL capacity or equivalent.6.6 Small Glass Filter Funnel.1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.02 on Wet Blue.Current edition approved Sept.1,2016.Published October 2016.Originallyapproved in 2001.Last previous edition approved in 2015 as D6714-01(2015).DOI:10.1520/D6714-16.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.7 Dessicator,of suitable size and design and charged withfresh dessicant.6.8 Weighing Vessels,of suitable size and design.6.9 Drying Oven,with accurate variable temperature con-trols.6.10 Hot Plate,with accurate variable temperature controls.6.11 Perchloric Acid Hood.7.Reagents7.1 Purity of ReagentsAnalytical Reagent(AR)gradechemicals shall be used in all tests.Unless otherwise indicated,it is intended that all reagents shall conform to specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society,4where such specifications are available.Othergrades may be used,provided it is first ascertained that thereagent is of sufficient