1、Designation: D 3897 91 (Reapproved 2006)Standard Practice forCalculation of Basicity of Chrome Tanning Liquors1This standard is issued under the fixed designation D 3897; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is intended to show how the results of thechromium analysis (Test Method D 3898) and the aciditydetermi
3、nation (Test Method D 3913) can be combined topermit calculation of the basicity of a chrome tanning liquor.1.2 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
4、and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 3898 Test Method for Chromic Oxide in Basic Chro-mium Tanning LiquorsD 3913 Test Method for Acidity in Basic Chromium Tan-ning Liquors3. Significance and Use3.1 B
5、asicity 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
6、 closely related to the tanning behavior of the solution.4. Procedure4.1 Determine the chromic oxide as described in TestMethod D 3898. Determine the acid as described in TestMethod D 3913.5. Results5.1 The basicity of the liquor shall be expressed accordingto the Schorlemmer system. In this system,
7、 the basicity is theper cent of the total chromic oxide that is combined withhydroxyl and is calculated as follows:Basicity, % 5A 2 BA3 100 (1)where:A = the amount of thiosulfate, as mL of 0.1 N solutionrequired to titrate the 25 mL aliquot as the specimen inTest Method D 3898,B = the amount of sodi
8、um hydroxide, as mL of 0.1 Nsolution required to titrate the 25 mL aliquot of thespecimen in Test Method D 3913.6. 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 determin
9、ation 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=PCR21 PA2(2)where:PA= precision of acidity in basic chromium tanningliquors,PCR= precision of chromic oxide in basic chr
10、omiumtanning liquors,PB= precision of basicity in basic chromium tanningliquors.6.2 For the reported reproducibility figures for the chromicoxide from Test Method D 3898 (d = 0.90 %) and for acidityfrom Test Method D 3913 (Procedure I, s = 1.84 %), dBisgiven as 2.05 %. This number has the units of b
11、asicity.Similarly, repeatability has d = 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; Schorlemmer1This practice is und
12、er the jurisdiction ofASTM Committee D31 on Leather andis the direct responsibility of Subcommittee D31.06 on Chemical Analysis.Current edition approved Oct. 1, 2006. Published November 2006. Originallyapproved in 1991. Last previous edition approved in 2001 as D 3897 - 91(2001).2For referenced ASTM
13、 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.3Hartford, W. H., The Journal of the Leather Chemists Assoc., Vol 56, 1961, p.568
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17、 If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 3897 91 (2006)2
