ASTM_D_3897_-_18.pdf

Designation:D389718Standard Test Method forCalculation of Basicity of Chrome Tanning Liquors1This standard is issued under the fixed designation D3897;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 is intended to show how the results ofthe chromium analysis(Test Methods D3898 or D6019)andthe acidity determination(Test Method D3913)can be com-bined to permit calculation of the basicity of a chrome tanningliquor.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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D3898 Test Method for Chromic Oxide in Basic ChromiumTanning LiquorsD3913 Test Method for Acidity in Basic Chromium TanningLiquorsD6019 Test Method for Determination of Chromic Oxide inBasic Chromium Tanning Liquors(Ammonium PersulfateOxidation)3.Significance and Use3.1 Basicity is a ratio.In any chromic salt solution,theelectrovalence of the chromium(+3)is satisfied by the hy-droxyl ions and by acid ions.The extent to which thiselectravalence is satisfied by the hydroxyl ions,expressed as apercentage,is the basicity.The basicity of a chrome tanningliquid is closely related to the tanning behavior of the solution.4.Procedure4.1 Determine the chromic oxide as described in TestMethod D3898 or D6019.Determine the acid as described inTest Method D3913.5.Results5.1 The basicity of the liquor shall be expressed accordingto the Schorlemmer system.In this system,the basicity is theper cent of the total chromic oxide that is combined withhydroxyl and is calculated as follows:Basicity,%5A 2 BA3100(1)where:A=the amount of thiosulfate,as mL of 0.1 N solutionrequired to titrate the 25 mL aliquot as the specimen inTest Methods D3898 or D6019,B=the amount of sodium hydroxide,as mL of 0.1 Nsolution required to titrate the 25 mL aliquot of thespecimen in Test Method D3913.6.Precision and Bias6.1 Because basicity is in effect a ratio,the precisionindexes are transmitted by the laws governing ratios.If theprecision of accuracy of the chromic oxide determination or ofthe titratable acidity is expressed in the same relative units;forexample,percent of value being determined,the precision withwhich the basicity is known will be:PB5=PCR21PA2(2)where:PA=precision of acidity in basic chromium tanning liquors,PCR=precision of chromic oxide in basic chromium tanningliquors,PB=precision of basicity in basic chromium tanning li-quors.6.2 For the reported reproducibility figures for the chromicoxide from Test Method D3898(=0.90%)and for acidity1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.06 on Chemical Analysis.Current edition approved Sept.1,2018.Published October 2018.Originallyapproved in 1991.Last previous edition approved in 2017 as D3897-17.DOI:10.1520/D3897-18.2For 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 from Test Method D3913(Procedure I,=1.84%),Bis givenas 2.05%,and for the reported reproducibility figures for thechromic oxide from Test Method D6019(=0.27%)and foracidity from Test Method D3913(Procedure 1,=1.84%),Bis given as 1.86%.This number has the units of basicity.Similarly,repeatability has =0.52%basicity.Caution shouldbe employed in insisting on extremely close agreementsbetween laboratories or replicates unless a background of highprecision has been established.37.Keywords7.1 basicity;chrome tanning liquor;SchorlemmerASTM International takes no position respecting the validity of any patent right