1、Designation: D 2810 07Standard Test Method forpH of Leather1This standard is issued under the fixed designation D 2810; 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 th
2、e year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method covers the determination of the pH ofall types of leather. This method
3、 does not apply to wet blue.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 and health practices and determine the applica-bility of regulatory limitations
4、prior to use.2. Terminology2.1 Definition of Term Specific to this Standard:2.1.1 The pH of a solution has been defined as the negativelogarithm of the hydrogen ion activity. A solution of pH 7 isneutral at 24C. Lower numbers indicate increasing acidity;higher numbers, increasing alkalinity.3. Signi
5、ficance and Use3.1 This test method is designed to measure the pH of adistilled-water extract of leather. This is considered to be ameasure of the acidity or alkalinity of the leather. Excessiveacidity or alkalinity may have a deleterious effect on the agingcharacteristics of leather.3.2 This test m
6、ethod is suitable for development, control,and service evaluation of leather.4. Interferences4.1 If the leather contains an excessive amount of fats orgreases or has been treated with a material to obtain waterrepellency, the wettability and consequently the extractabilitymay be affected.4.2 If the
7、specimen is difficult or impossible to wet, it maybe treated by any of the following procedures:4.2.1 A vacuum may be used to effect wetting.4.2.2 Mix with the required amount of water for 1 min in adisintegrator.24.2.3 Extract the weighed specimen with a fat solvent in aSoxhlet apparatus for 5 h. A
8、llow the specimen to air until allsolvent has evaporated; then proceed as outlined in Section 9.5. Apparatus5.1 pH Meter, either battery or line-operated, with a glasselectrode and reference electrode or suitable combinationelectrode. The meter shall have a resolution of 0.1/0.01 pHunit, and shall h
9、ave a relative accuracy of 60.1/0.01 pH unit.5.2 Analytical Balance, sensitive to 0.01 g.6. Reagents6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical
10、 Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise indica
11、ted, referencesto water shall be understood to mean distilled water or water ofequal purity. Distilled water shall have a pH value of not lessthan 5.5 nor more than 7.0 and shall give a residue of not morethan 0.5 mg, when 100 mL is evaporated and dried in aplatinum dish.6.3 Standard pH Solutions:46
12、.3.1 Alkaline Phosphate Buffer Solution (0.01 M trisodiumphosphate, pH = 11.72 at 25C)Dissolve 1.42 g of anhy-drous disodium hydrogen phosphate (Na2HPO4) in 100 mL ofa 0.1 N carbonate-free solution of sodium hydroxide (NaOH)and dilute to 1 L with water.1This test method is under the jurisdiction of
13、ASTM Committee D31 on Leatherand is the direct responsibility of Subcommittee D31.06 on Chemical Analysis. Thistest method was developed in cooperation with the American Leather ChemistsAssn. (Standard Method B 20 1969).Current edition approved April 1, 2007. Published May 2007. Originallyapproved i
14、n 1969. Last previous edition approved in 2001 as D 2810 01.2A Waring Blender has been found satisfactory.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, se
15、e Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Buffer salts and solutions prepared in accordance with National Bureau ofStandards recommendations are sold b
16、y reputable laboratory supply houses and maybe used.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3.2 Borax Buffer Solution (0.01 M, pH = 9.18 at 25C)Dissolve 3.81 g of sodium tetraborate decahydrate (Na2B4O710 H2O) in water and
17、dilute to 1 L.6.3.3 Hydrochloric Acid (pH = 1.10 at 25C)Add2gofconcentrated hydrochloric acid (HCl, sp gr 1.19) to 450 g ofwater. Standardize and dilute to 0.1 N.6.3.4 Phosphate Buffer Solution (0.025 M with respect toeach phosphate, salt pH = 6.86 at 25C)Dissolve 3.40 g ofmonobasic potassium phosph
18、ate (KH2PO4) and 3.55 g ofanhydrous dibasic sodium phosphate (Na2HPO4) in water anddilute to 1 L.6.3.5 Potassium Hydrogen Phthalate Buffer Solution (0.05M, pH = 4.01 at 25C)Dissolve 10.21 g of potassiumhydrogen phthalate (KHC8H4O4) in water and dilute to 1 L.7. Test Specimen7.1 The specimen shall co
19、nsist of from 2 to 5 g of leatherfrom a composite sample prepared according to an acceptedprocedure.58. Standardization8.1 Before the pH of the solution is measured, turn theinstrument on, allow it to warm up thoroughly, and bring toelectrical balance in accordance with the manufacturers in-structio
20、ns. Wash the glass and calomel electrodes and thebeaker three times with water and dry gently with clean,absorbent tissue. If a sleeve-type calomel reference electrode isused, form a fresh liquid junction by moving the sleeve.8.2 Set temperature dial to the temperature of the solution.Use manufactur
21、ers directions for establishing two point stan-dardization with standard pH solutions that read on either sideof the anticipated pH of the solution to be tested. Washelectrodes by immersing in three changes of water and estab-lish a fresh liquid junction after blotting electrodes if usingsleeve type
22、 electrode prior to testing each solution.8.3 Check for electrode drift with either of the buffers andrestandardize if necessary.9. Procedure9.1 Weigh the specimen in duplicate to the nearest 0.1 g andtransfer to 250-mL Erlenmeyer flasks.Add water in the amountof twenty times the mass of the specime
23、n. Stopper the flasksand agitate thoroughly. Let stand at the Standard LaboratoryTemperature, 23.0 6 1C (73.46 1.8F), with occasionalagitation for not less than 4 nor more than 18 h. Agitatethoroughly and transfer to a clean beaker or decant if possible.9.2 Determine the pH of the leather-water mixt
24、ure orsolution. First wash and blot the electrodes and establish afresh liquid junction if using a sleeve-type electrode. Immersethe electrodes in the test solution and read the meter to thenearest 0.01 unit. Clean the electrodes again and repeat withthe second test specimen.10. Report10.1 Report th
25、e following information:10.1.1 The pH of the sample shall be reported to the nearest0.05 pH unit as determined by the average of the resultsobtained from the specimens tested except when establishingrepeatability or reproducibility then report each determinationseparately to 0.01 pH units.11. Precis
26、ion and Bias11.1 RepeatabilityThe average difference between tworesults (each the average of duplicate determinations), obtainedby the same analysis on different days, will approximate 0.01pH units. Two such values should be considered suspect (95 %confidence level) if they differ by more than 0.03
27、pH units.11.2 ReproducibilityThe average difference between tworesults (each the average of duplicate determinations) obtainedby analysis in different laboratories will approximate 0.02 pHunits. Two such values should be considered suspect (95 %confidence level) if they differ by more than 0.06 unit
28、s.NOTE 1Variance analysis of the pH data is on file at ASTMHeadquarters as RR: D-31-1002. It was developed from a round-robin testinvolving five laboratories and four leathers.12. Keywords12.1 acidity; alkalinity; pHASTM International takes no position respecting the validity of any patent rights as
29、serted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time
30、by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will rec
31、eive careful consideration at a meeting of theresponsible technical committee, which you may attend. 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 Int
32、ernational, 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 thro
33、ugh the ASTM website(www.astm.org).5Acceptable procedures are published in the Journal of the Americal LeatherChemists Assn., JALCA, Vol 5, 1956, p. 497; or Offcial Methods of Analysis, Am.Leather Chemists Assn., available through the Office of Secretary-Treasurer,Campus Station, Cincinnati, Ohio 45221; or see ASTM Method D 2813, SamplingLeather for Physical and Chemical Tests, Annual Book of ASTM Standards,Vol15.04.D2810072
