1、Designation: D6739 11Standard Test Method forSilicapH Value1This standard is issued under the fixed designation D6739; 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
2、 year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is used to measure the pH of a 5 %silica/water suspension or mechanical dispersion and is indica-tive of the relative acidity or alkalinity of the silica
3、.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 app
4、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E70 Test Method for pH of Aqueous Solutions With theGlass ElectrodeE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Pr
5、actice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Significance and Use3.1 The pH level of silica, as measured by this test method,is known to affect the vulcanization of some rubber com-pounds. Refer to Test Method E70 for a fuller understanding ofpH and a m
6、ore detailed procedure for making pH measure-ments.4. Apparatus4.1 pH Meter, (digital is recommended), having an accuracyof 60.05 pH and equipped with a combination electrode.4.2 Mortar and Pestle.4.3 Beaker, glass, 150 cm3with watch glass.4.4 Magnetic Stirring Bar and Stirrer.5. Reagents5.1 Degasse
7、d, Neutral Water. Boil a container of eitherdistilled or deionized water for 10 min, cover, and allow to coolto room temperature, or purge the water with nitrogen gas for20 min using a fritted bubbler.5.2 Buffer Solutions, pH of 4.00, 7.00, and 10.00.6. Procedure6.1 Pulverize pelleted or granulated
8、silica to a fine powder,using a mortar and pestle.6.2Weigh5gofsilica to the nearest 0.1 g into a 150 cm3glass beaker.6.3 Add 100 cm3of degassed, neutral water.6.4 Cover the glass beaker with a watch glass and stir themixture for 5 min at room temperature.6.5 Standardize the pH meter with two buffer
9、solutions thatbracket the expected pH value of the silica. Rinse the electrodewith distilled water and wipe clean after each test.6.6 Place the electrode in the silica/water mixture, continu-ing to stir with the magnetic stirrer. When a constant pH isobtained, record the pH to the nearest 0.05 pH un
10、it.6.7 Rinse the electrode with distilled water. Store electrodein accordance with manufacturers instructions when not inuse.7. Report7.1 Report the following information:7.1.1 Identification of the sample, and7.1.2 Result obtained, reported to the nearest 0.1 unit.8. Precision and Bias38.1 The prec
11、ision of this test method is based on aninterlaboratory study conducted in 2010. Eleven laboratoriestested two types of silica samples. Every “test result” repre-sents an individual determination. Each laboratory was in-structed to report four replicate test results for each material.Practice E691 w
12、as followed for the design and analysis of thedata.8.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”isthe1This test method is under the jurisdiction of ASTM Committee D11 on Rubbe
13、rand is the direct responsibility of Subcommittee D11.20 on Compounding Materialsand Procedures.Current edition approved July 1, 2011. Published August 2011. Originallyapproved in 2001. Last previous edition approved in 2006 as D6739 01 (2006).DOI: 10.1520/D6739-11.2For referenced ASTM standards, vi
14、sit 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.3Supporting data have been filed at ASTM International Headquarters and maybe obtained by reque
15、sting Research Report RR:D11-1108.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.interval representing the critical difference between two testresults for the same material, obtained by the same operatorusing the same equipment on t
16、he same day in the samelaboratory.8.1.1.1 Repeatability limits are listed in Table 1.8.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more than the “R” valuefor that material; “R” is the interval representing the criticaldifference between two test resu
17、lts for the same material,obtained by different operators using different equipment indifferent laboratories.8.1.2.1 Reproducibility limits are listed in Table 1.8.1.3 The above terms (repeatability limit and reproducibil-ity limit) are used as specified in Practice E177.8.1.4 Any judgment in accord
18、ance with statements 8.1.1and 8.1.2 would have an approximate 95 % probability ofbeing correct.8.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.8.3 The precision statement was
19、 determined through statis-tical examination of 80 results, from ten laboratories, on twodifferent precipitated silica samples.9. Keywords9.1 pH; silicaASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Us
20、ers 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 by the responsible technical committee and must be reviewed ever
21、y 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 receive careful consideration at a meeting of theresponsible techni
22、cal 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
23、n, 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). Permission rights to photoco
24、py the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).TABLE 1 pHMaterialAverageARepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibilityLimitx srSRrRSilica A 6.61 0.01 0.07 0.04 0.21Silica B 6.74 0.01 0.08 0.01 0.22AThe average of the laboratories calculated averages.D6739 112
