ANSI T 529 OM-2009 Surface pH measurement of paper.pdf

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1、TAPPI/ANSI T 529 om-14 PROVISIONAL METHOD 1974 OFFICIAL METHOD 1982 REVISED 1998 REVISED 1999 REVISED 2004 REVISED 2009 REAFFIRMED 2014 2014 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume n

2、o liability or responsibility in connection with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published. Approved by the Standard Sp

3、ecific Interest Group for this Test Method TAPPI CAUTION: This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of these is to alert the user of the method to safety issues related to such use. The user is responsibl

4、e for determining that the safety precautions are complete and are appropriate to their use of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the use, disposal, or both, of chemicals which may present serious heal

5、th hazards to humans. Procedures for the handling of such substances are set forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the use of t

6、his method, the user must determine whether any of the chemicals to be used or disposed of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe use and disposal of these chemicals. Surf

7、ace pH measurement of paper 1. Scope 1.1 This non-destructive test may be used to measure the hydrogen ion concentration (pH) on the surface of the paper in books and documents that constitute the collections of libraries and government archives. 1.2 This method serves as an alternative to TAPPI T 5

8、09 “Hydrogen Ion Concentration (pH) of Paper Extracts - Cold Extraction Method,” and TAPPI T 435 “Hydrogen Ion Concentration (pH) of Paper Extracts - Hot Extraction Method,” because it avoids the destruction of printed material in the determination of the permanence expected for paper (see also 11.2

9、). 1.3 pH values obtained through the application of this method to sized materials such as writing, printing, and industrial papers reflect only the pH of the surface of these materials and should not be construed as pH values which may be determined by the cold water extraction method of the same

10、material (1). 2. Summary A flat combination electrode is immersed in a drop of water on the surface of the paper sample. The pH of the surface of the paper is determined with high accuracy and repeatability without the requirement of sample destruction (2,3). 3. Significance 3.1 Because the useful l

11、ife of most papers is primarily a function of the acidity of the paper (4,5), it is necessary that the concentration of the hydrogen ion in the paper be known (4) so that appropriate preservation and/or restoration techniques may be employed to extend the useful life of books and documents which are

12、 determined to be acidic. 3.2 Since books and documents (some of which are very valuable or irreplaceable) cannot be destroyed or otherwise defaced for the purpose of pH determination, a need exists for a convenient procedure which is accurate but T 529 om-14 Surface pH measurement of paper / 2 does

13、 not require destruction or extensive water soaking of the paper samples to be tested. This non-destructive method accomplishes this need (6,7,8,9). 4. Apparatus 4.1 Commercial pH meter, with flat combination electrode1, which can be immersed in a single drop of water. The pH meter must measure pH w

14、ith a precision of 0.1 pH unit and should include temperature compensation. 4.2 Backing material, non-absorbent material, such as gum rubber, to allow firm contact of electrode against surface of paper. 4.3 Absorbent cotton, to remove water after completion of test. 4.4 Timer, stopwatch or electric

15、timer. 4.5 Thermometer, 0-100C range. 4.6 Volumetric flasks, 1000 mL, for buffer solutions. 5. Reagents 5.1 Water. Reagent grade water used in this test method shall conform to ASTM Specification D 1193, Type I or II, Standard Specifications for Water (10). NOTE 1: Water meeting this specification i

16、s typically sold by many manufacturers for use in HPLC, residue analysis, and spectrometry, and is packaged under nitrogen. 5.2 Standard buffer solutions: 5.2.1 Potassium hydrogen phthalate buffer, pH 4.01 at 25C; dissolve 10.21 g of KHC8H4O4(A.C.S. primary standard or certified grade) in water and

17、dilute to 1000 mL. NOTE 2: The buffer capacity of this buffer solution is rather low and the solution should be protected from contamination with acids or alkalis. Its pH, however, is not affected by atmospheric carbon dioxide. Replace the buffer solution every six weeks or if mold appears. 5.2.2 Ph

18、osphate buffer, pH 6.86 at 25C: dissolve 3.40 g of monobasic potassium phosphate (KH2PO4, A.C.S. primary standard) and 3.55 g of anhydrous dibasic sodium phosphate, Na2HPO4, in carbon dioxide-free water and dilute to 1000 mL. When protected from undue atmospheric exposure, this buffer solution is qu

19、ite stable. NOTE 3: The Na2HPO4will absorb moisture from the air at relative humidities exceeding 40% at 25C and should be dried at 100 to 130C for 2 h before use. 5.2.3 Borax buffer, pH 9.18 at 25C: dissolve 3.81g of sodium tetraborate Na2B4O7 10 H2O in carbon dioxide-free water and dilute to 1000

20、mL. NOTE 4: The dilution value of this buffer solution is so small that changes in the water content of the borax are usually of no concern. Precautions should be taken to protect solution form prolonged atmospheric exposure and subsequent CO2absorption. The shelf life of this solution is about one

21、month. 5.2.4 Propriety buffer solutions: These are commercially available and may be purchased in a ready-to-use solution form. The pH of these buffer solutions, however, must be accurately known if they are used. 6. Calibration 6.1 Connect the combination surface electrode to the pH meter. 6.2 Soak

22、 the combination surface electrode for at least 2 h in distilled water. 1Names of suppliers of testing equipment and materials for this method may be found on the Test Equipment Suppliers list, available as part of the CD or printed set of Standards, or on the TAPPI website general Standards page. 3

23、 / Surface pH measurement of paper T 529 om-14 6.3 Calibrate the pH meter at pH 4.01 using phthalate buffer and at 6.86 using phosphate buffer, following the instructions in the pertinent pH meter instruction manual. The borax buffer is used for calibration when an unusually high pH is indicated. 7.

24、 Sampling and test specimens 7.1 From each test unit of the sample obtained in accordance with TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Containerboard or Related Product,” select at random at least five different sheets, pages, or leaves. Since this procedure is normall

25、y applied to material that is not to be subjected to destructive testing, the test unit may be in the form of a book or bound pages. 7.2 The application of this procedure does not require cutting or any other destructive method of sampling. 8. Procedure 8.1 Follow instructions under 6.1. 8.2 Follow

26、instructions under 6.2. 8.3 Back the specimen with a non-absorbing, resilient material such as gum rubber. Such a backing material allows the electrode to be contacted firmly and evenly with the surface of the paper. 8.4 Place one drop of room temperature (25 5C) reagent water on a leveled surface o

27、f the specimen (do not spread the water droplet on the paper surface as this is accomplished when the electrode is lowered into the water). 8.5 Immerse the measuring surface of the electrode in the water droplet. Although equilibration is accomplished in about 2 min, it is desirable to allow about 1

28、0 min of immersion before each reading, but no immersion time greater than 30 min has yet been determined to be necessary even on highly sized or coated paper. 8.6 Determine pH according to the manufacturers instructions for the pH meter used. Read the pH to the nearest 0.1 pH unit. 8.7 After record

29、ing the pH value, immediately remove the electrode vertically from the water droplet. 8.8 Using absorbent cotton, blot the area of paper wetted by the droplet and allow to air dry before storage or further treatment. NOTE 5: In the case of pH measurements of inner pages of whole books, allow the blo

30、tted area to dry before closing the book. 8.9 Wash the electrode with reagent water after each measurement. Recalibrate frequently and store the electrode in reagent water. 9. Report Report the average of five determinations to the nearest 0.1 pH unit. 10. Precision 10.1 The following estimates of r

31、epeatability and reproducibility are based on data from an interlaboratory trial involving four laboratories and 8 different paper and board materials. The trial was conducted in November 1997 using the “om-88” revision of this method. Testing is based on 5 determinations per test result and 1 resul

32、t per lab per material. Repeatability (within the lab) r = 0.13 pH units Reproducibility (between labs) R = 0.41 pH units 10.2 Repeatability and reproducibility are estimates of the maximum difference (at 95%) which should be expected when comparing test results for materials similar to those descri

33、bed above under similar test conditions. These estimates may not be valid for different materials or testing conditions. 11. Additional information 11.1 Effective date of issue: April 30, 2014. 11.2 Other TAPPI procedures for the determination of the pH of paper are TAPPI T 435 (hot extraction) and

34、TAPPI T 509 (cold extraction). T 529 om-14 Surface pH measurement of paper / 4 11.2.1 The values obtained by these methods have been found to be somewhat different from surface pH measurements because of the rate of diffusion to the surface of hydrolyzed alum or other sulfates in the paper. 11.2.2 I

35、n the preparation of this method, surface pH measurements have been found to approximate more closely those values obtained by the cold extraction method than those obtained by the hot extraction method. 11.3 Other methods of pH determination have been discussed by Launer (11), Browning (4), Minor (

36、12), and Barrow (13). These methods, however, either require destruction of the specimen or have been found to be unreliable as surface measurements (6). 11.4 It has also been determined that highly sized, calendered or coated papers require longer equilibration time to obtain a stable pH value sinc

37、e the nature of the surface slows the wetting action and subsequent hydrogen ion extraction from the paper fibers. 11.5 The 1994 revision of this method includes revision of the precision statement and inclusion of ASTM Type I or II water. Only editorial changes were made in the 2009 version. 12. Ke

38、ywords Paper, pH Literature cited 1. Torbjorn, H., “Various Methods for Determining the pH Values on Paper Surfaces,” Norwegian Research Institute of Paper Industry, 1960, p.5. 2. Schwabe, K., “Progress in pH Measuring Technique,” VEB publ Technik Berlin, 1953, p. 23. 3. Stamm, A.J., “A Comparison o

39、f Three Methods for Determining the pH of Wood and Paper,” Forest Products Journal, July 1961, pp. 310-312. 4. Browning, B.L. and Ulm, R.W.K., “The Nature and Measurement of Paper Acidity,” Paper Trade Journal 102(8): 69(1936). 5. Launer, H.F., “Determination of the pH Value of Papers,” J. Research

40、(National Bureau of Standards) 22:663 (139). 6. Palenius, I., Olander, P., and Juselius, A., “Reliability of the Determination of the pH Value of Pulp, Paper and Board,” Paperi Ja Puu 44:85 (1962). 7. Flynn, J.H. and Smith, L.E., “Comparative pH Measurements on Papers by Water Extraction and Glass E

41、lectrode Spot Tests,” Tappi 44(3): 223 (1961). 8. Hudson, F.L. and Miller, W.D., “The Use of Flat Headed Glass Electrodes for Measuring the pH of Paper,” Svensk Paperstid 62: 83 (1959). 9. Huber, V.C., “The Use of Flat Headed Glass Electrode for Measuring the pH of Paper,” Papier 18: 45 (1964). 10.

42、ASTM Standard D-1193, “Standard Specification for Reagent Water,” American Society for Testing and Materials, Philadelphia, PA. 11. Launer, H.F., “Retention of Aluminum Ions and Hydrogen Ions in Paper,” J. Research (National Bureau of Standards) 22: 553 (1939). 12. Minor, J.E. and Farmer, M., “The p

43、H Test for Paper,” The Paper Industry and Paper World 22: 565 (1940). 13. Barrow, W.J., “Spot Testing for Unstable Modern Book and Record Papers,” Permanence/Durability of the Book - VI, 1969, p. 11. References Taylor, J.E., “An Apparatus for the Continuous Production of Triple Distilled Water,” Journal of Chemical Education 37: 204 (1960). ASTM D 778-93, American Society for Testing and Materials, Philadelphia, PA. Your comments and suggestions on this procedure are earnestly requested and should be sent to the TAPPI Standards Department.