1、Designation: D 4471 00 (Reapproved 2004)Standard Test Method forPyridine Bases in Cresylic Acid by Direct Titration1This standard is issued under the fixed designation D 4471; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of 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 test method covers the determination of pyridineand other basic nitrogen impurities in crude and refinedcre
3、sylic acids streams, including mixtures.1.2 This test method is applicable for pyridine base levels of0.001 % to 0.5 %.1.3 The following applies to all specified limits in thisstandard: For purposes of determining conformance with thisstandard, an observed value or a calculated value shall berounded
4、 off “to the nearest unit” in the last right-hand digitused in expressing the specification limit, in accordance withthe rounding-off method of Practice E 29.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user
5、of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specific hazardstatements, see Section 8.2. Referenced Documents2.1 ASTM Standards:2D 3852 Practice for Sampling and Handling Phenol,Cresols, and Cresyl
6、ic AcidD 4790 Terminology of Aromatic Hydrocarbons and Re-lated ChemicalsE 29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications2.2 Other Document:OSHA Regulations, 29 CFR, paragraphs 1910.1000 and1910.120033. Terminology3.1 For definitions of terms used i
7、n this test method seeTerminology D 4790.4. Summary of Test Method4.1 This test method is a direct, nonaqueous titration tech-nique utilizing perchloric acid in acetic acid as titrant and thecresylic acid itself as titration solvent. Endpoints may beestablished potentiometrically as well as by indic
8、ator so thatthe method is applicable to highly colored as well as lightercolored materials. This test method will detect basic compo-nents other than pyridine bases should they be present. Allbasic compounds detected by this procedure are calculated andexpressed as percent pyridine.5. Significance a
9、nd Use5.1 The pyridine base content of cresylic acids is importantin certain applications. This test method may be used as a toolfor quality control and specification purposes by producers andusers.6. Apparatus6.1 Titrimeter or pH meter, equipped with glass and calomelelectrodes. The pair of electro
10、des shall be mounted to extendwell below the liquid level. Storage in water between titrationsis essential because prolonged immersion in nonaqueous me-dium significantly deadens response.6.2 Buret, 50-mL capacity.6.3 Magnetic Stirrer, with TFE-fluorocarbon or glass cov-ered stirring bar.6.4 Autotit
11、ration Equipment may be used if available.7. Reagents7.1 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 Reagents of the American Chemical Society,1Thi
12、s test method is under the jurisdiction of ASTM Committee D16 onAromatic Hydrocarbons and Related Chemicals and is the direct responsibility ofSubcommittee D16.02 on Oxygenated Aromatics.Current edition approved June 1, 2004. Published June 2004. Originallyapproved in 1985. Last previous edition app
13、roved in 2000 as D 4471 00.2For 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.3Available from U.S. Government Pr
14、inting Office Superintendent of Documents,732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.where such specifications are available.4Other grades may beused, provided it is f
15、irst ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Perchloric Acid Titrant (0.02 N in glacial acetic acid)Add 1.8 mL of 70 % perchloric acid (HClO4) to 1 L of glacialacetic acid and mix well. To standardize, weigh
16、accurately0.0800 to 0.0950 g of primary standard potassium acidphthalate in glacial acetic acid and titrate potentiometrically orto the indicator endpoint, as described in 10.2. Calculate thenormality, N, of the perchloric acid solution as follows:N 5WV 3 0.2041where:W = weight of potassium acid pht
17、halate, g, andV = volume of perchloric acid titrant consumed, mL.7.3 Potassium Acid Phthalate (KH C8H8O4), primarystandardDry for2hat110C.7.4 Quinaldine Red Indicator Solution Dissolve 0.2 g ofquinaldine red indicator in 100 g of glacial acetic acid.7.5 Titration SolventGlacial acetic acid (CH3CO2H)
18、 maybe used as an additional titration solvent in order to decreasethe viscosity of a particular sample or to keep it from freezing.8. Hazards8.1 Consult current OSHA regulations and suppliers Mate-rial Safety Data Sheets, and local regulations for all materialsused in this test method.9. Sampling9.
19、1 Samples of the material shall be taken in accordancewith Practice D 3852.10. Procedure10.1 Weigh an appropriate amount of cresylic acid sampleinto the titration beaker. (A sample size of 100 g is suggestedif the expected pyridine base content is in the range of 0.001 to0.070 %.) Place a stirring b
20、ar in the beaker and, if desired, addabout 100 mL of titration solvent.10.2 The specimen is titrated with perchloric acid titrant andthe endpoint determined by either of the following methods:10.2.1 IndicatorA few drops of quinaldine red indicator isadded to the solution. The titration is terminated
21、 when the redcolor disappears and the color of the sample returns to itsoriginal hue.10.2.2 PotentiometricThe electrodes are inserted into thespecimen and the observed potentials are plotted as a functionof the titrant volume consumed. The point where DE/DV is thegreatest is taken as the endpoint.10
22、.3 Repeat 10.1 through 10.2, but with no specimen toobtain a reagent blank when titration solvent is used.11. Calculation11.1 Results are calculated as weight percent pyridine, P,asfollows:P 57.91 3 N 3 VS2 VB!Wwhere:N = normality of the perchloric acid titrant,VS= titrant consumed for the sample, m
23、L,VB= titrant consumed for the reagent blank, mL, andW = specimen weight, g.12. Report12.1 Report the percent of pyridine bases to the nearest0.001 %.13. Precision and Bias13.1 PrecisionThe following criteria shall be used forjudging the acceptability of results.13.1.1 Intermediate Precision (within
24、 laboratory) Whenusing the visual endpoint in this test method, results obtainedby different analysts in the same laboratory should be suspectwithin 95 % confidence limits if they differ by more than 2.8 %of the average of values determined. When using the potentio-metric endpoint in this test metho
25、d, results obtained bydifferent analysts in the same laboratory should be suspectwithin 95 % confidence limits if they differ by more than 2.2 %of the average of values determined.13.1.2 Reproducibility (between laboratories)When us-ing the visual endpoint in this test method, results obtained byana
26、lysts in different laboratories should be suspect within 95 %confidence limits if they differ by more than 6.8 % of theaverage of values determined. When using the potentiometricendpoint in this test method, results obtained by analysts indifferent laboratories should be suspect within 95 % confiden
27、celimits if they differ by more than 13.9 % of the average ofvalues determined.13.1.3 BiasThe bias of this test method cannot be deter-mined because no referee method is available to determine thetrue value.14. Keywords14.1 cresols; cresylic acids; nitrogen bases; phenol; pyridinebases; tar acids4Re
28、agent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaa
29、nd National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D 4471 00 (2004)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determi
30、nation 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 by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or wi
31、thdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that y
32、our 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 4471 00 (2004)3
