ASTM_D_4901_-_99_2009.pdf

Designation:D490199(Reapproved 2009)Standard Practice forPreparation of Solution of Liquid Vegetable Tannin Extracts1This standard is issued under the fixed designation D4901;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 practice covers the preparation of a solution ofliquid extract that is to be used in the tannin analysis of thatextract.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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D4904 Practice for Cooling of Analytical SolutionsD6404 Practice for Sampling Vegetable Materials Contain-ing Tannin2.2 ALCA Methods:A10 Preparation of Solution of Liquid Extracts33.Summary of Practice3.1 The practice describes a technique found useful in thepreparation of analytical strength solutions from samples ofliquid vegetable tannin extracts.4.Significance and Use4.1 The concentration of tannin in extracts must be reducedto analytical strength(4 g tannin per L)for analyses.4.2 Vegetable tannin extracts are heterogeneous mixtures ofcomponents with varying solubility.4.3 The solubility of such extracts is influenced by tempera-ture and concentration,which affect the degree of dispersionand size of the component particles.4.4 While the solubility is better in hot water than in coldwater,it is appropriate to dissolve and disperse an extract in hotwater and then let the solution cool slowly to standard roomtemperature.5.Apparatus and Reagents5.1 Formaldehyde40%solution.5.2 Tolueneassay$99.5%.5.3 Flask,1 Lvolumetric.The ClassAtype,with upper bulbin neck,is especially suitable for this work.6.Test Specimen6.1 The specimen shall consist of an aliquot of the sample,prepared as described in Practice D6404,sufficient to give asolution containing as nearly as possible,4 g of tannin per L(not less than 3.75 g,nor more than 4.25 g,per L).7.Procedure7.1 Prepare samples of liquid extracts,as described inPractice D6404,and allow to come to room temperature.Thoroughly mix at room temperature and transfer specimen toa tared container and stoppered to prevent loss of moisture.Return no material which has been removed from the samplefor any other purpose(for example,for determination ofspecific gravity,etc.)to the sample.Care must be taken thatdried material around the neck of the stopper of the samplebottle does not contaminate the sample or specimen.Weigh thecontainer and specimen to the nearest 0.1 mg.NOTE1Shaking by hand is rarely sufficient;mechanical shaking,especially with a clinical-type shaker for 10 min,is preferred.In the caseof very viscous extracts,a stirrer has to be used,in which case care mustbe taken to avoid the loss of moisture.7.2 Pour approximately 200 mL of distilled water at 95Cinto a 1 Lvolumetric flask and immediately transfer specimens,quantitatively,into the flask with distilled water at 95C.Assoon as the specimen has been transferred,mix the contents ofthe flask by swirling.Add sufficient distilled water at 95C to1This practice is under the jurisdiction ofASTM Committee D31 on Leather andis the direct responsibility of Subcommittee D31.01 on Vegetable Leather.Thispractice has been adapted from and is a replacement for Method A10 of the OfficialMethods of the American Leather Chemists Association.Current edition approved April 1,2009.Published July 2009.Originallyapproved in 1989.Last previous edition approved in 2004 as D4901 99(2004).DOI:10.1520/D4901-99R09.2For 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 452210014.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 bring the volume to approximately 900 mL,and mix thesolution again by swirling.The temperature of the solutionimmediately after this mixing shall not be less than 80C.Ifnecessary,apply heat to keep the solution above 80C.7.3 If the solution is likely to ferment(myrabolans ordivi-divi),add 1 mL of 40%formaldehyde and mix thesolution again.In any event,the addition of from 3 to 4 dropsof toluene is recommended to ensure against mold growthduring the overnight cooling.7.4 Prepare duplicate solu