ASTM_D_6410_-_99_2020.pdf

Designation:D641099(Reapproved 2020)Standard Test Method forDetermining Acidity of Vegetable Tanning Liquors1This standard is issued under the fixed designation D6410;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 determining the acidity oftannery liquors made up from vegetable tanning materials.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:2D4904 Practice for Cooling of Analytical SolutionsD6404 Practice for Sampling Vegetable Materials Contain-ing Tannin2.2 ALCA Methods:A25 Analysis of Tannery Liquors33.Terminology3.1 Definitions:3.1.1 tannery liquorwater solutions containing vegetabletannin that are made up and used in a vegetable tannery.4.Summary of Test Method4.1 An analytical solution is prepared from the sample oftannery liquor(Practice D6404).Specimen aliquots from thisanalytical solution are then analyzed for total acidity by one oftwo titrametric methods.5.Significance and Use5.1 This test method is used to determine one of thechemical properties of tannery liquors which are relevant forthe vegetable tanning process and influence the astringency ofvegetable tanning liquors.The astringency of liquors is depen-dent upon the solids and tannin content and the acidity.Thistest method provides a standard procedure for determining thetotal acidity for any sample of vegetable tanning liquor.5.2 The specimens are aliquots from the analytical solutionprepared from the sample of tannery liquor collected for thispurpose.5.3 The total acidity of the liquor sample is determined byone of two titrametric procedures described in this test method.6.Apparatus and Reagents6.1 Analytical Solution:6.1.1 Flask,1 Lvolumetric.ClassAflasks with a bulb in theneck(M.C.A.type)are especially suitable for this work.6.1.2 Hydrometer,preferably with a Barkometer scale(thatis,a scale calibrated in Bk).The three digits to the right of thedecimal point on a standard specific gravity reading are equalto the Barkometer scale reading.That is,a sp.gr.of 1.200equals 200Bk and a sp.gr.of 1.020 equals 20Bk.6.2 Acidity DeterminationMethod I:6.2.1 Graduated Cylinder,glass-stoppered,graduated tocontain 250 mL.6.2.2 Gelatin Solution,1%,neutral to bromocresol purple.The addition of 25 mL of 95%ethyl alcohol per litre isrecommended to prevent frothing.The solution shall be ad-justed to neutrality to bromocresol purple with 0.1 N aceticacid or 0.1 N sodium hydroxide.1This test method is under the jurisdiction of ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.01 on Vegetable Leather.Thistest method has been adapted from and is a replacement for the acidity determina-tion portion of Method A25 of the Official Methods of the American LeatherChemists Association.Current edition approved Dec.1,2020.Published December 2020.Originallyapproved in 1999.Last previous edition approved in 2014 as D6410 99(2014).DOI:10.1520/D6410-99R20.2For 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.3Official Methods of the American Leather Chemists Association.Availablefrom the American Leather Chemists Association,University of Cincinnati,P.O.Box 210014,Cincinnati,OH 45221-0014.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.16.2.3 Kaolin4,acid-washed kaolin clay which conforms tothe following specifications:6.2.3.1 Suspend 1.0 g kaolin in 100 mL distilled water.ThepH value should be between 4.5 and 6.0 after 5 min.6.2.3.2 Amixture of 2.0 g kaolin and 200 mL distilled waterare shaken for 10 min