1、Designation: D 778 97 (Reapproved 2002)An American National StandardStandard Test Methods forHydrogen Ion Concentration (pH) of Paper Extracts (Hot-Extraction and Cold-Extraction Procedures)1This standard is issued under the fixed designation D 778; the number immediately following the designation i
2、ndicates 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover two procedure
3、s for determi-nation of the hydrogen ion concentration, expressed in terms ofpH, of an aqueous extract of paper.1.2 These test methods may be applied to writing, printing,and sized industrial papers.1.3 These test methods are not intended to be used fordetermination of pH of insulating papers, for t
4、hat see TestMethods D 202.1.4 The test methods appear as follows:SectionTest Method ApH of Paper (Unfiltered Extract) AfterExtraction for1hinCold (25 6 5C) Water11.1Test Method BpH of Paper (Unfiltered Extract) AfterExtraction for1hinBoiling Water11.21.5 Specifications may be based on Test Method A
5、or TestMethod B, or both.1.6 Where a specification or specific instructions or agree-ment to use only one of these test methods is absent, determinepH using both procedures, and interpret results based onSection 12.1.7 This standard does not purport to address all of thesafety concerns, if any, asso
6、ciated 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:D 202 Test Methods for Sampling and Testing UntreatedPaper
7、 Used for Electrical Insulation2D 585 Practice for Sampling and Accepting a Single Lot ofPaper, Paperboard, Fiberboard and Related Product3D 1193 Specification for Reagent Water4D 1293 Test Methods for pH of Water4D 1968 Terminology Relating to Paper and Paper Products3E 70 Test Method for pH of Aqu
8、eous Solutions With theGlass Electrode5E 122 Practice for Choice of Sample Size to Estimate aMeasure of Quality for a Lot or Process63. Terminology3.1 Definition: Definitions shall be in accordance withTerminology D 1968 and the Dictionary of Paper.74. Summary of Test Methods4.1 Test Method A consis
9、ts of the extraction of a 1-g testspecimen in 70 mL of cold distilled water (25 6 5C) for 1 h,and determination of pH without filtration using a commercialpH meter.4.2 Test Method B consists of the extraction of a 1-g testspecimen in 70 mL of boiling distilled water for 1 h, followedby cooling of th
10、e extract and determination of the pH withoutfiltration using a commercial pH meter.5. Significance and Use5.1 The acidity or alkalinity of a paper sample extract isimportant because of the effect of paper acidity or paperalkalinity on the permanence of the paper. Although acidity oralkalinity may b
11、e determined by titration the pH is often moreindicative of the stability of paper than is the total acidity oralkalinity.6. Apparatus6.1 pH MeterUse a pH meter of Type II or Type III asspecified in Test Methods D 1293. In general terms this is a pHmeter accurate to 0.01 pH units with temperature co
12、mpensationsuitable for making pH measurements over the 0 to 14-pHrange.6.2 Reflux condensers, preferably water cooled, West orAllihn Type, with 300-mm jackets, standard taper inner jointsand drip tips; or air condensers, 10-mm diameter and 1000 mmlong with ST inner joints and drip tips, ST joints to
13、 fit the flasks(required on hot-extraction procedure, only).1These test methods are under the jurisdiction of ASTM Committee D06 onPaper and Paper Products and are the direct responsibility of Subcommittee D06.92on Test Methods.Current edition approved Dec. 10, 1997. Published November 1998. Origina
14、llyapproved in 1944. Last previous edition approved in 1993 as D 778 93.2Annual Book of ASTM Standards, Vol 10.01.3Annual Book of ASTM Standards, Vol 15.09.4Annual Book of ASTM Standards, Vol 11.01.5Annual Book of ASTM Standards, Vol 15.05.6Annual Book of ASTM Standards, Vol 14.02.7Available from th
15、e Technical Association of the Pulp and Paper Industry, P.O.Box 105113, Atlanta, GA 30348.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Reagents7.1 Distilled WaterThe distilled water used in these testmethods must comply with Ty
16、pe II or Type III reagent water asspecified in Specification D 1193.7.2 Standard Buffer Solutions:7.2.1 If buffer solutions are prepared in the laboratory, theirpreparation and corporation must comply with applicablesections of Test Method E 70 or Test Methods D 1293. Someknowledge of the expected p
17、H may be required to indicatewhich buffers (pH values) will be required for use.7.2.2 Commercially available pH buffers may be used ifdesired. Common pH values are 4.0, 7.0, and 10.0. Purchasethe ones appropriate for samples being tested.8. Sampling8.1 Acceptance SamplingAcceptance sampling shall be
18、 inaccordance with Practice D 585.8.2 Sampling for Other PurposesThe sampling and thenumber of the test specimens depends on the purpose of thetesting. Practice E 122 is recommended.9. Test Specimen9.1 A composite evaluation is considered appropriate forthese test methods unless otherwise specified.
19、9.2 Take an equal number of sheets (one or more) from eachtest unit, but not less than a total of five sheets, and combine thesheets from all test units. Holding the sheets at one end, cut andcross-cut the other end into 5 to 10-mm square.9.3 If the paper is more than 0.012 in. (0.30 mm) inthickness
20、, or greater in apparent density than 0.90 g/cm3, thespecimen must be split by delamination into thickness of notover 0.008 in. (0.20 mm) before it is cut into the small squares.9.4 From each quantity of cut paper, weigh a test specimenof 1 6 0.01 g, using an equal amount of material from eachlayer
21、in cases where the sample has been delaminated asrequired in 9.3. Do not include any material in the specimenthat has been touched by the fingers.9.5 Perform determinations at least in duplicate. In specialcases where it is necessary to evaluate different portions of thelot separately, take a portio
22、n from each test unit of the sampleand perform duplicate determinations on each portion indepen-dently, using the procedure specified for the composite.10. Calibration10.1 Calibration of the pH meter must be done followingapplicable sections of Test Methods D 1293 or Test MethodE 70. The instruction
23、 manual of the specific pH meter must beconsulted for any operations specific to that pH meter.11. Procedure11.1 Test Method ApH of Paper (Unfiltered Extract) AfterExtraction for1hinCold (25 6 5C) Water:11.1.1 Transfer the test specimen to a 100-mL beaker. Addabout 5 mL of cold (256 5C) distilled wa
24、ter and maceratewith a flattened glass stirring rod until the specimen is wet.11.1.2 Add more water to bring the volume to 70 mL, stirwell, cover with a watch glass, and allow to stand for1hat256 5C. The specimen may stand for 3 or 4 h (1)7if nocontamination occurs.11.1.3 When making referee or rese
25、arch tests, pass purenitrogen or CO2-free air through the solution until the pH ismeasured.NOTE 1Air may be cleaned by passing it through a gas washing bottlecontaining at least 200 mL of 3N H2SO4and then through a tower orU-tube containing ascarite or soda lime, 120 to 150 mm long.11.1.4 Measure th
26、e pH on the prepared extract (see 11.1.1through 11.1.3) as specified in 11.3.11.2 Test Method B pH of Paper (Unfiltered Extract) AfterExtraction for1hinBoiling Water:11.2.1 Transfer the test specimen to a 125-mL Erlenmeyerflask. Add about 70 mL of distilled water, stir well, and attachthe condenser.
27、NOTE 2Water-cooled condensers are desirable. The air condensersmay be used if the temperature of the hot plate can be controlled asindicated in 11.2.2.11.2.2 Place the flask on the hot plate. Reduce the hot platetemperature as necessary using the hot plate controls and boilgently for 1 h, taking car
28、e not to exceed the capacity of thecondenser. The temperature should be maintained between 98and 100C (208 and 212F).11.2.3 At the end of the extraction period cool the flask inrunning water (to about 35 to 40C), with the condenser tube inplace and its upper end protected by a loosely fitted smallbe
29、aker. Replace the condenser with a glass stopper and cool atroom temperature. Transfer the mixture to a 100-mL beaker.11.2.4 Transfer the extracts for referee or research tests tothe 100-mL beakers while hot. Pass nitrogen or CO2-free airthrough these extracts while cooling and until the pH ismeasur
30、ed.11.2.5 Measure the pH on the prepared extract (see 11.2.1through 11.2.4) as specified in 11.3.11.3 pH Measurement:11.3.1 Keep a nitrogen or CO2-free air cap over the solutionduring pH measurement. Stir and measure to 0.1 pH unit thepH of the unfiltered mixture in accordance with the instructionsf
31、or the pH meter used.11.3.2 Through observation, make certain that no plies ofpaper adhere to the electrodes during pH measurement.11.3.3 Before recording the pH, leave the electrodes in thesolution until there is no measurable drift in 30 s.11.3.4 Wash the electrodes with distilled water after each
32、measurement and recalibrate frequently.11.3.5 Keep the electrodes, buffer, test solution, and washwater at the same temperature and set the compensator for thistemperature.12. Interpretation of Results12.1 The pH of an extract of a paper sample indicates theextent to which components of the paper al
33、ter the hydrogen-hydroxyl equilibrium of pure water. In the case where the papersample consists of highly purified cellulose having a low levelof inorganic or noncellulosic organic impurities or additives,the alteration of this equilibrium will be slight, and a pH near7, the neutrality point on the
34、pH scale is likely. Additionally,the difference in pH measured by the two test methodsdescribed will be small.D 778 97 (2002)212.2 In cases where inorganic or noncellulosic organicmaterials were present in the raw materials from which a paperwas made, or were deliberately added during processing, th
35、epH of the resulting paper extract will generally show greaterdeviation from pH 7 than in the case of the highly purifiedcellulosic paper described in 12.1. Further, the direction of thedeviation from pH 7 and its magnitude cannot be predictedwithout information regarding the identity and quantity o
36、fnoncellulosic materials present. In addition, the relationship ofthe results from the two test methods cannot be predicted forsuch samples.12.3 When these test methods are referenced in specifica-tions, an understanding of the noncellulosic materials presentand the specific information needs of the
37、 buyer and seller mustbe considered in deciding whether Test Method A or TestMethod B, or both, must be required.12.4 When these test methods are used for analysis ofmaterials of unknown origin or prior history, use of both TestMethods A and B is highly recommended, as suggested in 1.6.12.5 It must
38、be clear to the user of these test methods that anunderstanding of the composition of the paper being tested andthe specific information required are the only unequivocalfactors that can be used to determine whether Test Method A orTest Method B, or both, are best suited for a given analysis.12.6 Ex
39、amples of the relationship between results from TestMethod A and Test Method B for specific papers are in12.6.1-12.6.7. Additional information may be found in thetechnical literature for those wishing to pursue this topic.12.6.1 The pH of the extract of a paper sized with rosin andalum is typically
40、lower by 0.5 to 0.6 pH units when tested byTest Method B in comparison with data when Test Method Ais used. This is believed to be caused by hydrolysis of thesizing components in boiling water to release hydrogen ions oracidic materials (1)8.12.6.2 On the other hand, it has been reported thatmelamin
41、e-formaldehyde resin hydrolyzes during extraction byTest Method B to release alkaline products that tend to increasethe pH value of the extract when compared to the resultmeasured by Test Method A (1).12.6.3 The consequence of 12.6.1 and 12.6.2 is that when apaper is made containing rosin and alum s
42、izing as well asmelamine-formaldehyde resin, the pH measured by TestMethod A may be higher than, lower than, or nearly equal tothat measured by Test Method B, depending upon the relativeamounts of the various noncellulosic materials present.12.6.4 Other materials are believed to exhibit similar ef-f
43、ects.12.6.5 Some believe that the hydrolysis occurring when TestMethod B is used simulates changes that might occur duringnatural aging, and that values obtained by Test Method Bcorrelate with paper-ink reactions in printing (2, 3).12.6.6 Barrow (4), however, found that Test Method Acorrelated bette
44、r with his accelerated aging tests.12.6.7 In published data relating to the use of pH measure-ment by Test Method A or B in studying paper stability,Palenius (5), Kelly (6), and Wilson (7, 8) and co-workers reportvalues on a variety of papers where results by Test Method Brange from 2.5 units higher
45、 to 1.5 units lower than thosedetermined by Test Method A.12.7 It must be emphasized that no generalizations regard-ing the relationship of results by Test Method A and B ispossible, nor can any simple rules of interpretation be pro-vided.13. Report13.1 Report the following information:13.1.1 The av
46、erage of the two determinations to the nearest0.1 pH unit, and13.1.2 The test method used (Test Method A or Test MethodB) for each result reported.14. Precision and Bias14.1 Precision:14.1.1 Test Method A (Cold Extraction):14.1.1.1 Repeatability (Within a Laboratory)60.1 pHunits for comparison of te
47、st results from the same test unit,where each test result is the average of two determinations, oneeach on separate sheets from the same test unit. Repeatabilityon test units from the same composite sample, as specified inthis test method, should be equal to or smaller than this figure.14.1.1.2 Repr
48、oducibility (Between Laboratories )60.5pH units.14.1.2 Test Method B (Hot Extraction):14.1.2.1 Repeatability is identical with that for Test MethodA, in accordance with 14.1.1.1.14.1.2.2 Reproducibility is identical with that for TestMethod A in accordance with 14.1.1.2.14.1.3 These limits of repeat
49、ability and reproducibility arethe critical limits between which results obtained under theconditions specified in these test methods may be expected tolie 95 % of the time.14.1.4 For additional information regarding expected preci-sion of pH measurements of aqueous solutions, consult TestMethod E 70.14.1.5 The precision values stated above are based upon 14reports on the TAPPI Collaborative Reference Program forpaper for samples in the pH range from 5.0 to 6.0. Similarprecision may be expected at other pH levels in the range from4.0 to 10.0.14.1.6 The user of these
