ANSI T 421 OM-1997 Qualitative (including optical microscopic) analysis of mineral filler and mineral coating of paper.pdf

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1、T 421 om-12 OFFICIAL STANDARD 1927 FOURTH REVISION 1973 OFFICIAL TEST METHOD 1983 REVISED 1991 REVISED 1997 WITHDRAWN - 2003 REINSTATED 2012 2012 TAPPI The information and data contained in this document were prepared by a technical committee of the Association.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 ass

2、ume no 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 Standa

3、rd Specific 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 respo

4、nsible 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

5、 health 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

6、 of this 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.

7、 Qualitative (including optical microscopic) analysis of mineral filler and mineral coating of paper 1. Scope1.1 This method describes procedures which may be used for the qualitative determination and identification of the mineral constituents of filled and coated papers. 1.2 Due to the similarity

8、in chemical composition and physical size and shape of some of the various possible constituents contained in a given paper specimen, more precise quantitative methods may at times be required for positive identification. 1.3 It is recommended that one become thoroughly familiar with this method by

9、analyzing paper samples of known mineral component content. 2. Summary Qualitative chemical analyses of the mineral component of a paper specimen, as described in Sections 4 through 11 of this method, serve to identify the ions of any such minerals. The results may then be interpreted in terms of th

10、e minerals themselves. Direct identification of some of these minerals or their ions is frequently possible using the optical microscopic examination procedures described in Sections 12 through 18 of this method. 3. Significance of qualitative chemical analysis method 3.1 The presence of such minera

11、l matter is indicated by the amount and appearance of the ash content of the specimen being tested. If the ash content is less than 1% (or only slightly above) and is light and fluffy in character, added mineral filler is probably absent. If more than 1%, and the ash is dense and compact, added fill

12、er is likely, unless waste papers have been used in the furnish. At times this may be determined microscopically as outlined in TAPPI T 401 T 421 om-12 Qualitative (including optical microscopic) analysis / 2 of mineral filler and mineral coating of paper “Fiber Analysis of Paper and Paperboard.” 3.

13、2 Some mineral fillers and/or coating pigments are chemically altered during specimen ashing. Carbonates, sulfites, and sulfides are examples of those which are quite susceptible to such changes. For this reason, unashed specimens should be examined for such components. Low temperature plasma ash ma

14、y be helpful in some cases. 3.3 In order to interpret qualitative ash tests with greater assurance, it is important to estimate the relative amounts of various constituents found. In this connection, for example, the light voluminous character of an aluminum hydroxide precipitate should be taken int

15、o account when relating its quantity to that of a heavy, dense precipitate like barium sulfate. With flame and colorimetric tests, it is particularly difficult to judge the relative quantities of the constituents present, and these should be interpreted with special care. 3.4 Although the wet method

16、s described herein are basic to the technology, it is now common in many instances to use techniques based on X-ray diffraction, X-ray fluorescence, and electron microscopy to determine the pigment content of various papers. X-ray methods can be used, for example, to identify the crystal form of TiO

17、2 (anatase or rutile) and to estimate the amount present (using known standards for calibration). Also diffraction patterns of minerals such as clay and talc can be helpful. 3.5 More recent developments in the field include the use of infrared techniques, especially internal reflectance methods and

18、emission spectroscopy, as tools to identify the inorganic constituents of paper and paper coatings. Newer electron microscopy techniques, including scanning electron microscopy, electron microprobe, and Auger analysis, are useful additions to the list, as are atomic absorption and flame emission spe

19、ctroscopy. 3.6 The electron microscope can provide clearly identifiable pictures of the pigment in a redispersed paper sample allowing an experienced operator to distinguish among the various natural and precipitated fillers and coating pigments in use today. 3.7 For those having access to such equi

20、pment, analysis procedures and techniques are available from the equipment manufacturers and from the literature. 4. Apparatus for qualitative chemical analysis 4.1 Crucible, platinum, with lid. For use in 8.7.1 and in ashing the sample being examined. Porcelain or silica crucibles may be used if th

21、eir weight does not change under the ignition conditions. 4.2 Electric muffle furnace, controlled to maintain a temperature of 525 25C. 4.3 Electric laboratory oven, controlled to maintain a temperature of 150 3C. 4.4 Blowpipe. 4.5 Platinum wire loop. 4.6 Spot plate, black, glazed. 4.7 Other apparat

22、us: beakers, 250-mL; watch glass; volumetric flasks, 100-mL; filter funnels, and an ashless, acid washed filter paper with fine porosity, slow flow rate, and a particle retention size of 2.5 m for use in critical gravimetric analysis. 5. Reagents for qualitative chemical analysis 5.1 Acetic acid, gl

23、acial, 99.7% CH3COOH, sp gr 1.05; also approximately 1N solution. (Add approximately 6.0 mL glacial acetic acid to 50 mL water in a volumetric flask and dilute to 100-mL mark.) 5.2 Ammonium sulfate, (NH4)2SO4. 5.3 Charcoal block. 5.4 Cobalt nitrate solution. Dissolve 8 g of Co(NO3)2 6H2O in 100 mL o

24、f water. 5.5 Diphenylthiocarbazone (dithizone) solution. Dissolve 10 mg dithizone in 100 mL carbon tetrachloride, being careful to avoid contact with the CCl4. 5.6 Hydrochloric acid, concentrated HCl, sp gr 1.19; also approximately 2N. (Add 15 mL concentrated HCl to approximately 75 mL water in a 10

25、0-mL volumetric flask and dilute to 100-mL mark.) 5.7 Hydrogen peroxide, 30% H2O2, or a solution of 3% USP H2O2used in proportionately greater quantities. NOTE 1: Extreme caution should be used when handling 30% H2O2solution as it is very active when in contact with skin. Eye protection should be wo

26、rn. 5.8 Lead acetate paper. Immerse strips of filter paper in a saturated solution of Pb(C2H3O2)2 3H2O; withdraw from solution and allow to air dry. 3 / Qualitative (including optical microscopic) analysis T 421 om-12 of mineral filler and mineral coating of paper 5.9 Lime water, saturated solution.

27、 Dissolve about 0.2 g of Ca(OH)2in 100 mL of water and filter. 5.10 Magnesium reagent. Dissolve 0.5 g of p-nitrobenzeneazoresorcinol in 100 mL of 1% NaOH solution. 5.11 Microcosmic salt solution. Dissolve 5 g of sodium ammonium phosphate (NaNH4HPO44H2O) in water and dilute to 100 mL. 5.12 Morin (3,5

28、,7,2,4-pentahydroxyflavanone). Saturated solution of morin in methyl alcohol. 5.13 Potassium ferrocyanide solution. Dissolve 15 g of K4Fe(CN)63H2O in 1000 mL of water. 5.14 Potassium hydroxide, approximately 2N solution. Dissolve 11.2 g of KOH in 75 mL water; cool and dilute to 100 mL. 5.15 Sodium c

29、arbonate, powdered Na2CO3. 5.16 Sodium hydroxide, approximately 2N solution. Dissolve 8 g NaOH in 75 mL water; cool and dilute to 100 mL. 5.17 Sulfuric acid, concentrated H2SO4, sp gr 1.84. Also approximately 5% (3 mL concentrated H2SO4added to about 75 mL of water, then diluted to 100 mL). 5.18 Oth

30、er reagents: ammonium hydroxide, concentrated NH4OH, sp gr 0.90; ammonium chloride, 10% solution NH4Cl; ammonium oxalate, 3.5% solution (NH4)2C2O4.H2O; barium chloride, 10% solution BaCl2O; potassium dichromate, 4% solution K2Cr2O7. 6. Sampling Obtain a sample of the paper to be tested in accordance

31、 with TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Fiberboard, or Related Product.” 7. Test specimens 7.1 From each test unit cut, for each complete determination, test specimens of sufficient size to yield at least 0.15 g of ash. 7.2 An additional specimen of each test uni

32、t should be available for testing without previous ashing. 8. Procedure 8.1 An outline scheme of the qualitative procedure is given in Figs. 1-4. 8.2 Sulfite, sulfide, and carbonate (unignited coating or paper sample (Fig. 1). 8.2.1 Treat a portion of the unignited coating or paper sample in a small

33、 beaker or test tube with 2N HCl. Note whether effervescence takes place and the odor of any escaping gas. Liberation of SO2and H2S indicates the presence of sulfites and sulfides, respectively. Warm the contents of the beaker and test the vapor with moistened lead acetate paper. The development of

34、a metallic gray or black color confirms the presence of sulfide. In the absence of sulfides, add either a small crystal of potassium dichromate or a few drops of a 4% solution of dichromate to a small portion of the HCl solution of the sample. A green coloration indicates the presence of a reducing

35、agent, in this case probably a sulfite. NOTE 2: Mixtures of sulfites and sulfides are not known to be used in loading or coating paper. 8.2.2 If sulfites and sulfides are absent, effervescence alone is a good indication of the presence of a carbonate, which may be confirmed by holding a glass rod wi

36、th a drop of saturated lime water just above the solution. Cloudiness (milky) appearance of the supported drop indicates the presence of CO2. This precipitate may later dissolve. A confirmatory test of CO2in the presence of sulfites is to oxidize the sulfites to sulfates by adding to the contents of

37、 the beaker, a weak solution of iodine (about 0.1N), drop by drop, until the entire liquid is colored yellow. Then test with lime water on a glass rod as described previously in this paragraph. T 421 om-12 Qualitative (including optical microscopic) analysis / 4 of mineral filler and mineral coating

38、 of paper Fig. 1. Qualitative analysis of sulfite, sulfide, and carbonate. 8.3 Ashing. 8.3.1 Ash the specimen at a temperature of 525C (lower than the 925C temperature used in TAPPI T 413 Ash in Paper and Paperboard,” see also 8.3.2). This lower temperature is used to prevent or minimize the alterat

39、ion of the composition of various coating or filling components. 8.3.2 For coated paper where separate analyses of filling material and coating minerals are desired, remove the coating by an enzymatic stripping procedure. Evaporate to dryness the aqueous mixture containing the coating minerals and a

40、sh this residue as well as the base stock as in 8.3.1. NOTE 3: If synthetic coating adhesives have been used in place of starch or casein, enzymatic stripping will not be effective. In this case, scrape the coating from the surface with a razor blade. 8.4 Aluminum hydrate; sodium silicoaluminate; Al

41、, Ca, or Mg silicates; Ca or Ba sulfates; TiO2(Fig. 2). 8.4.1 To approximately 0.05 g of ash add 10 g of (NH4)2SO4and 20 mL of concentrated H2SO4. Cover with a watch glass and boil vigorously for at least 3 min. White fumes, indicating decomposition of the H2SO4, will be noted during this period. 8.

42、4.2 Considerable undissolved matter indicates the presence of one or more of the following: sodium silicoaluminate; Ca, Al, or Mg silicate; aluminum hydrate or diatomaceous earth. If this strongly acidic, hot solution is clear, the absence of these materials is confirmed. Calcium and/or barium sulfa

43、te will be dissolved unless the specimen being tested weighs more than 0.05 g; TiO2will be in solution. 8.4.3 Decant some of the supernatant liquid into a small beaker, cool, and dilute it cautiously with a portion (up to about five times its volume) of cold water. The formation of a precipitate on

44、dilution indicates the presence of barium sulfate, which is relatively soluble in hot concentrated H2SO4. 8.4.4 Mix the diluted acidic mixture (8.4.3) with the remainder of the undiluted strongly acidic mixture (8.4.2) from the concentrated H2SO4treatment and add sufficient water to make the ratio o

45、f H2O to H2SO4about 5 to 1. If the original H2SO4solution (8.4.1) was clear, dilute it 5 to 1 by adding water cautiously after cooling. Filter and retain any residue for examination under 8.4.5. To the cooled filtrate add 1 mL of 30% H2O2. A deep yellow or orange color indicates the presence of tita

46、nium, the depth of color being proportional to the amount of titanium present. If only a very light yellow color is produced, it may be caused by titanium from clay, or derived from dissolved titanium in the mill water. 5 / Qualitative (including optical microscopic) analysis T 421 om-12 of mineral

47、filler and mineral coating of paper Fig. 2. Qualitative analysis of aluminum hydrate; sodium silicoaluminate; Al, Ca, or Mg silicates; Ca or Ba sulfates; TiO2. 8.4.5 The presence of barium or calcium in any insoluble residue (8.4.4) can be determined by a flame test as follows: Dip a clean platinum

48、wire into the moist residue, retained on the filter paper, and hold it in a Bunsen flame. A green flame indicates the presence of barium, a red flame indicates calcium, and a yellow to colorless flame indicates aluminum and/or magnesium silicates or aluminum hydrate. NOTE 4: CaSO4is quite soluble in

49、 dilute H2SO4and may not be observed at this step. 8.4.6 The flame test can be used to detect soluble calcium, barium, and sodium in the clear solution obtained in 8.4.3. Dilute a small portion of the solution cautiously with an equal volume of water. Dip a clean platinum wire into the solution and hold it in a Bunsen flame. A green flame indicates barium, a red flame indicates calcium, and a strong yellow flame indicates sodium. 8.5 Sulfide, sulfite, and carbonate (ash sample ignited at 525C) (Fig.3) 8.5.1 Treat 0.1 g of ash (8.3.1) with 10 mL of water and 5 mL