1、T 252 om-12 PROVISIONAL METHOD 1976 OFFICIAL TEST METHOD 1985 REVISED 1990 REVISED 1998 REVISED 2002 REAFFIRMED 2007 REAFFIRMED 2012 2012 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume no l
2、iability 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 Speci
3、fic 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 responsible f
4、or 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 health
5、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 this
6、 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. pH and
7、electrical conductivity of hot water extracts of pulp, paper, and paperboard 1. Scope This procedure provides for the extraction of pulp, paper, and paperboard samples using boiling reagent water followed by determination of the pH and conductivity of the extract. 2. Significance 2.1 pH measurement
8、of the extract indicates presence of either acidic or basic ions which could contribute to potential degradation of the cellulose in the end product. 2.2 Conductivity measurement indicates the level of residual ionic impurities in pulp and thus not only shows the effectiveness of washing in the pulp
9、 manufacturing process but also identifies the suitability of pulp for use in electrical and antitarnish product applications. Extract conductivity of highly purified (high alpha) pulps increases on aging from the time of manufacture. 3. Apparatus 3.1 pH meter, any commercial pH meter that includes
10、a glass electrode and a reference electrode or a “combination electrode.” The meter must be capable of indicating pH to 0.1 unit or less. 3.2 For referee testing, the pH meter and electrodes shall conform to ASTM Standard D 1293, Standard Test Method for water, Section 10, Apparatus, with the pH met
11、er being of Type II, Type III, or Type IV of Table 2 of ASTM D 1293. 3.3 Erlenmeyer flasks, 500 mL, with standard taper joint. 3.4 Water-cooled condensers, with standard taper joints. 3.5 Fritted glass funnel, with suction flask. 3.6 Miscellaneous glassware: graduated cylinder, 1000 mL; 50 mL beaker
12、 for pH; tall-form beakers, 100 or 200 mL, for conductivity measurements. NOTE 1: Proper cleaning of the glassware is essential. Soap or detergents should be avoided, and acid cleaning with ample rinsing is recommended. T 252 om-12 pH and electrical conductivity of hot water / 2 extracts of pulp, pa
13、per, and paperboard 3.7 Electric hot plate. 3.8 Conductivity bridge, with a dip-type cell having platinum electrodes securely mounted 1 cm apart. The face area of each electrode must be at least 2 cm2. The electrodes should be platinized if measurements are made at low frequency (60 Hz). A commercia
14、l conductivity meter may also be used. See also Additional Information, Section 11.3. 3.9 Constant temperature bath, maintained at 25 0.5C. 3.10 Thermometer, accurate to 0.25C. 4. Reagents 4.1 Reagent water. 4.1.1 ASTM D 1193, Specification for Reagent Water, describes procedures for preparing and t
15、esting water of the quality required by this test method. For referee testing, the term “water” as used in this test method should be understood to mean Type II or Type I reagent water as defined in ASTM D 1193. 4.2 Standard buffer solutions. NOTE 2: For the purposes of this test method, all chemica
16、ls must be of reagent grade and conform to the specifications of the committee on Analytical Reagents of the American Chemical Society, where such specifications are available. Other grades may be used provided that it is first ascertained that the reagent is of sufficient high purity to permit its
17、use without lessening the accuracy of the determination. 4.2.1 Potassium hydrogen phthalate buffer, pH 4.01 at 25C. Dissolve 10.21 g of HKC8H4O4in water and dilute to 1000 mL. NOTE 3: As the buffer capacity of this solution is rather low, protect the solution from contamination with acids and alkali
18、es; however, the pH is not affected by atmospheric carbon dioxide. The solution should be replaced after six weeks, or earlier if mold appears. 4.2.2 Phosphate buffer, pH 6.86 at 25C. Dissolve 2.40 g of monobasic potassium phosphate, KH2PO4,and 3.55 g anhydrous dibasic sodium phosphate, Na2HPO4, in
19、carbon dioxide-free water and dilute to 1000 mL. NOTE 4: The Na2HPO4will absorb moisture at relative humidities exceeding about 40% at 25C and should be dried for 2 h at 110-130C before use. This buffer solution is quite stable when protected from undue exposure to the atmosphere. 4.2.3 Potassium hy
20、drogen tartrate buffer, pH 3.56 at 25C. Add 1 g of KHC4H4O6to 100 mL water at about 30C, shake for several minutes, cool to 25C, decant, and filter to secure an approximately saturated solution. NOTE 5: The pH is insensitive to changes of concentration, so elaborate precautions to ensure saturation
21、are unnecessary. The temperature of saturation may vary from 22 - 28C. Excess solid should be removed as it may cause erratic potentials at the liquid junctions. The tartrate solution is subject to mold, accompanied by an increase in pH. Consequently, it cannot be used for more than a few days unles
22、s a preservative, such as a crystal of thymol, is added. 4.2.4 Borax buffer, pH 9.18 at 25C. Dissolve 3.81 g of Na2B4O7 10H2O in carbon dioxide-free water and dilute to 1000 mL. The Na2B4O7 need not be dried before use, but should be kept tightly sealed to prevent moisture or CO2uptake before use. N
23、OTE 6: The concentration of this solution is so low that changes in the water content of the borax will not affect the pH of the solution; however, exposure to atmospheric carbon dioxide may change its value. It is advisable to replace the solution about a month after preparation. 4.2.5 Commercial b
24、uffers at 4, 7, and 10 pH. These are permitted provided they are of the proper pH value. 4.3 Potassium chloride solution. Prepare a 0.01N solution using reagent grade KCl which has been dried for 2 h at 105C. Cool in a desiccator and dissolve 0.7455 g in reagent water and make up to 1000 mL in a vol
25、umetric flask at 20C. 3 / pH and electrical conductivity of hot water T 252 om-12 extracts of pulp, paper, and paperboard 5. Calibration of equipment 5.1 pH meter. Before measuring the pH of the extract, calibrate the meter using phthalate buffer for pH 4.01 and phosphate buffer for pH 6.86. Followi
26、ng the manufacturers instructions for calibration, or the procedures in ASTM D 1293, Standard Test Method for pH of Water, or ASTM E 70, Standard Test Method for pH of Aqueous Solutions with the glass electrode. The borax and tartrate buffers are usually used for calibration when specimen extracts s
27、how an unusually high or low pH. 5.2 Conductivity cell. 5.2.1 To replatinize electrodes, immerse the dip cell in a solution containing approximately 30 g/1000 mL of chloroplatinic acid and 0.10 g of lead acetate. Electrolyze with a current density of 30 mA/cm2for a period of 8 min. Reverse the curre
28、nt every 2 min. Wash the electrodes thoroughly with reagent water. Stand the cell in reagent water and measure conductivity initially and after 10 min. If conductivity increases, wash the cell again. Keep the cell in reagent water when not in use. 5.2.2 To determine the cell constant, place a tall-f
29、orm beaker containing 0.01N KCl in the 25C bath. Measure the resistance of the solution at 25C, being certain electrodes are completely immersed. 5.2.3 The cell constant K is calculated as follows: K = CR where C = conductivity of 0.01N KCl at 25C, or 1.41 10-1S/m R = resistance measured, ohms 6. Sa
30、mpling and test specimen 6.1 From the grab sample or composite sample, cut or tear a quantity into pieces, using clean gloves to prevent sample contamination. 6.1.1 Moisture content. Weigh 5 g of pulp, paper, or paperboard sample to the nearest 0.01 g in a weighing bottle and dry to constant weight
31、in the unstoppered weighing bottle at 105C (3 h). Cool in a desiccator, stopper, weigh, and calculate percent oven-dry moisture. 6.1.2 Specimen. Weigh (to the nearest 0.01 g) an amount of pulp, paper, or paperboard equivalent to 1.5 g oven-dry of sample. Test at least two specimens. 7. Procedures 7.
32、1 Transfer the test specimen to a 500-mL glass-stoppered Erlenmeyer flask. Add 150 mL of reagent distilled water from a graduated cylinder and connect the flask to a water-cooled condenser 7.2 Place the flask on a hot plate adjusted to boil so as not to exceed the capacity of the condenser. Boil for
33、 10 min. 7.3 Pour the hot extract into a fritted glass funnel attached to a clean suction flask. Transfer the filtrate from the suction flask to a clean Erlenmeyer flask. Close the Erlenmeyer flask with a rubber stopper and cool to 25C. 7.4 pH measurement. Pour about 50 mL of the cooled filtrate int
34、o a small beaker and measure the pH while keeping a nitrogen, or carbon dioxide - free, air cap over the solution (see Fig. 1). NOTE 7: Air may be cleaned by passing it through a gas washing bottle containing at least 200 mL of 3N H2SO4and then through a tower or U-tube containing ascarite or soda l
35、ime, 120-150 mm long. 7.5 Conductivity. Transfer the balance of the extract to a clean, tall-form beaker suspended in the 25C water bath. Check the extract temperature and, when the temperature is 25 0.5C, place the dip cell in the extract, making certain the electrodes are completely immersed. Meas
36、ure the resistance on the most sensitive scale of the conductivity bridge. Move the dip cell up and down in the extract solution and repeat readings until they show a constant value. For a blank, treat 50 mL of reagent water through steps 7.1 to 7.5. T 252 om-12 pH and electrical conductivity of hot
37、 water / 4 extracts of pulp, paper, and paperboard Fig. 1. pH measurement. 8. Report 8.1 Report pH readings, as the average of two determinations, to the nearest 0.1 pH unit. 8.2 Report conductivity as the average of two determinations, as: For a conductivity bridge, having electrodes 1 cm apart, wh
38、ere units of measurement of resistance are as “ohms.” Conductivity, mS/m = 310BRKRKwhere: K = cell constant R = resistance of extract solution, ohms RB= resistance of water blank, ohms For commercial conductivity meters, where units of measurement of conductance are as “siemens” (same as “mhos”): mS
39、/m, for the sample - mS/m, for the blank = mS/m, to be reported See also Additional information, Section 11.3. 9. Precision 9.1 Precision. The following estimates of repeatability and reproducibility are based on data from an interlaboratory trial involving six different materials. The trial was con
40、ducted in December 1997 using the “om-90” revision of this method. Testing is based on two determinations per test result and three results per lab per material. 5 / pH and electrical conductivity of hot water T 252 om-12 extracts of pulp, paper, and paperboard pH Measurements (in pH units) Material
41、 Grand Repeatability Reproducibility Labs Mean r R Included 80# Offset (white) 9.63 0.24 0.65 4 Pulp A 9.47 0.22 0.78 4 Pulp B 8.52 0.23 0.48 4 42# Linerboard 7.52 0.32 1.11 4 20# Bond (white) 6.96 0.31 0.31 4 Bleached Paperboard 5.40 0.35 0.50 4 Avg 0.28 0.64 Conductivity Measurements (in mS/m) Mat
42、erial Grand Repeatability Reproducibility Labs Mean r R Included 80# Offset (white) 7.78 0.37 4.27 5 Pulp A 6.75 0.39 4.00 5 Pulp B 4.64 0.60 3.36 5 20# Bond (white) 3.82 0.17 2.25 5 42# Linerboard 3.66 0.21 2.76 5 Bleached Paperboard 2.91 0.21 1.75 5 Avg 0.33 3.07 Repeatability and reproducibility
43、are estimates of the maximum difference (at 95%) which should be expected when comparing test results for materials similar to those described above under similar test conditions. These estimates may not be valid for different materials or testing conditions. 9.2 The above are in accordance with the
44、 definitions of these terms in TAPPI T 1200 “Interlaboratory Evaluation of Test Methods to Determine TAPPI Repeatability and Reproducibility.” 10. Keywords pH, Electrical conductivity, Hot water extracts, Pulp, Paper, Paperboard 11. Additional information 11.1 Effective date of issue: April 24, 2012
45、. 11.2 Related method: ASTM D 202 “Untreated Paper Used for Electrical Insulation,” American Society for Testing and Materials, Philadelphia, PA. 11.3 In using the various types of conductivity meters available, it is necessary to clearly define the units obtained, so as to properly correct test res
46、ults to mS/m (millisiemens/meter). The dimensions of the cell must be considered when converting conductance to conductivity. It has been an unfortunate but common practice to drop the dimensional unit when expressing cell constants. For example: for a conductivity meter having a cell constant of 1
47、mho/cm, readings would be multiplied by 100 to obtain mhos/m: T 252 om-12 pH and electrical conductivity of hot water / 6 extracts of pulp, paper, and paperboard 1.0 mhos/m = 0.01 mhos/cm Also, it should be remembered that the term “mho” is the same as “siemens” and is the same as “1/ohm.” Thus: 1m
48、mho/m = 1 m siemens / m = 1mS/m 11.4 Applicable documents: ASTM D 1193, ASTM D 1293, ASTM E 70. Appendix: Treatment of reagent water A.1 Entrained material can usually be removed by redistilling with a high-capacity glass still. When distilling from solutions with added chemicals, great care must be
49、 taken to avoid entrainment of volatile contaminants. Stills with double heads or traps should be used. Antibump material should be added and the distilling rate reduced. A.2 To remove acid or organic material, distill the water from a solution containing 1 g of KMnO4and 4 g of NaOH per 1000 mL. This does not remove ammonia so that any volatile alkalinity is best removed by distilling from very dilute sulfuric acid. Your comments and suggestions on this procedure are earnestly requested and s
