1、Designation: D 984 97 (Reapproved 2002)Technical Association of Pulp and Paper IndustryStandard Method T 406 Su-72An American National StandardStandard Test Methods forReducible Sulfur in Paper1This standard is issued under the fixed designation D 984; the number immediately following the designatio
2、n indicates 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 the determ
3、ination of reduciblesulfur in paper and paperboard within the context of the givendefinitions.1.1.1 Method BThe semiquantitative method indicates thegeneral level of reducible sulfur with limited accuracy.1.1.2 Method AThe quantitative method gives a measureof the reducible sulfur with much greater
4、accuracy.2,31.2 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.
5、Referenced Documents2.1 ASTM Standards:D 585 Practice for Sampling and Accepting a Single Lot ofPaper, Paperboard, Fiberboard, and Related Product4D 644 Test Method for Moisture Content of Paper andPaperboard by Oven Drying4D 1968 Terminology Relating to Paper and Paper Products4D 2043 Test Method f
6、or Silver Tarnishing by Paper43. Terminology3.1 DefinitionsDefinitions shall be in accordance withTerminology D 1968 and the Dictionary of Paper.54. Summary of Test Methods4.1 Method B, semiquantitative method, involves the reduc-tion of various forms of sulfur to hydrogen sulfide and thedevelopment
7、 of a dark spot of lead sulfide on the filter paperimpregnated with lead acetate. The intensity of the spot iscompared with spots developed from standards and is propor-tional to the concentration. No colorimeter or spectrophotom-eter is needed for this method.4.2 Method A, the quantitative method,
8、uses the identicalreduction system to generate hydrogen sulfide, but the sulfideis precipitated by alkaline cadmium sulfate and then convertedto methylene blue by reaction with acidicp-aminodimethylaniline in the presence of ferric chloride. Themethylene blue is measured spectrophotometrically and t
9、heintensity is compared with standards prepared in similarmanner.5. Significance and Use5.1 The test methods outlined are not necessarily a measureof how much a given test material will tarnish polished metals.When tested by these methods, paper that has less than0.0008 % reducible sulfur, may be as
10、sumed to be nontarnishingas far as sulfur is concerned, but if more than 0.0008 %, thisdoes not necessarily mean that tarnishing will occur, becausesulfur compounds which may not cause staining are reduced bythe treatment with the subsequent evolution of hydrogensulfide. If more than 0.0008 % reduci
11、ble sulfur is found, or ifthe effect of that or other materials causing stains on silver isdesired, the paper should be subjected to an acceleratedtarnishing test (see Test Method D 2043).NOTE 1If the pH of the paper is low (for example, 4.0 to 4.5 (coldextraction) as little as 0.0002 % of reducible
12、 sulfur may cause tarnishingof imitation gold bronze prints; whereas, if the pH were higher, (forexample, on brush-coated art paper) a much higher quantity of sulfurmight be tolerated.5.2 The test methods described do not give the total sulfurcontent, nor the total reducible sulfur content, nor are
13、theyintended to. They are limited to the reducible sulfur contentdetermined under the conditions of the test (that is, a fairlymild reduction system).35.2.1 Those forms of sulfur believed to be “reducible” underthe test conditions are (1) sulfide (released by the acid, notactually reduced), (2) elem
14、ental sulfur, (3) thiosulfate, (4) otherpolythionates or polysulfides, and (5) perhaps sulfite. Sulfate isexcluded.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 a
15、pproved Dec. 10, 1997. Published November 1998. Originallypublished as D 984 48 T. Last previous edition D 984 92 (1996).2Sobolev, I., Bhargava, R., Gosuntov, N., and Russell, R., Tappi 39(9):628(1956).3Chazin, J. D., “Colorimetric Determination of Reducible Sulfur in Paper andPaperboard,” Tappi, Jo
16、urnal of the Technical Association of the Pulp and PaperIndustry, TAPPI, Vol 53, No. 8, 1970, p. 1514.4Annual Book of ASTM Standards, Vol 15.09.5Available from the Technical Association of the Pulp and Paper Industry, P.O.Box 105113, Atlanta, GA 30348.1Copyright ASTM International, 100 Barr Harbor D
17、rive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Sampling6.1 Obtain the sample in accordance with Practice D 585.6.2 A minimum of6gofsample is required to providetriplicate test specimens.6.3 Do not touch the test area of sample or test specimenswith the fingers; handle with cle
18、an forceps only.7. Test Specimens7.1 From each test unit of the sample, cut and weigh2gtothe nearest 1 mg for each test unit.7.2 Determine the moisture content in accordance with TestMethod D 644.METHOD AQUANTITATIVE MEASUREMENT8. Apparatus8.1 Reaction Apparatus (Fig. 1), consisting of a 500-mLround
19、-bottom three-necked flask as illustrated, equipped with agas inlet tube adapter with perforated bulb, a 60-mL pear-shaped funnel, a 200-mm West condenser, a side-arm adapter,and a heating mantle with variable power supply.8.2 Absorption Apparatus (Fig. 1), consisting of a 100-mLamber or low-actinic
20、 flask in a suitable ice bath.8.3 Colorimeter or Spectrophotometer to read at 660 to 670nm equipped with 1-in. cells or 25 to 50-mm cuvettes.8.4 Pipets1, 2, 5, and 10-mL serological or bacteriologi-cal (blow-out).8.5 Other Equipment100 and 1000-mL volumetric flasks;medicine droppers; 10 and 100-mL g
21、raduated cylinders; for-ceps; 10.0-mL volumetric pipets.8.6 DisintegratorA blender or other such rotating-bladedevice with a small volume container, if possible.8.7 Optional EquipmentA constant-temperature bath,maintained at 20 to 25C.9. Reagents and Materials9.1 Purity of ReagentsReagent grade chem
22、icals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.6Other grades may beused, provided it is first ascertaine
23、d that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.9.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean distilled water.9.3 Aluminum Foil, 1145 alloy, plain (or aluminum weigh-ing pans), not o
24、ver 0.01 in. (0.25 mm) sulfur-free.9.4 Amine Solutions:9.4.1 Stock Amine SolutionDissolve 25 g ofp-aminodimethylaniline sulfate (N,N-dimethyl-p-phenylenediamine sulfate) in 75 mL of cold sulfuric acid(1 + 1) and dilute to 100 mL with the (1 + 1) acid.9.4.2 Dilute Amine SolutionPipet 2.5 mL of the st
25、ocksolution into a 100 mL volumetric flask and dilute to the markwith sulfuric acid (H2SO4)(1 + 1).9.5 Cadmium Hydroxide Absorption SuspensionDissolve4.3 g of cadmium sulfate (3CdSO48H2O) in water; add 0.3 gof sodium hydroxide (NaOH) dissolved in water and 10 g ofarabinogalactan: dilute to 1000 mL a
26、nd stir well. This is asaturated solution of cadmium hydroxide; the suspension isswirled before pouring off an aliquot.9.6 Ferric Chloride SolutionDissolve 100 g of ferricchloride hexahydrate (FeCl36H2O) in water and dilute to 100mL.9.7 Nitrogen Gas, sulfur-free.9.8 Phosphoric AcidConcentrated phosp
27、horic acid(H3PO4) (sp gr 1.69) sulfur-free.9.9 Sodium Sulfide Standard Solutions (use water deaeratedwith nitrogen).9.9.1 Stock SolutionDissolve 1.56 g of sodium sulfidenonahydrate (Na2S9H2O) (use large crystals which appeardry) in the deaerated water and dilute to 1000 mL. Pad thespace over the sol
28、ution with nitrogen, and renew each time thesolution is used. Solution should be stable for 1 month.9.10 Working Solution Pipet 10.0 mL of stock solutioninto a 1000-mL volumetric flask and dilute to the mark with thedeaerated water. 1 mL of this solution contains 2 g of sulfur(that is, solution is 2
29、 ppm in sulfur). Prepare solution daily.NOTE 2This solution or the stock solution may be standardized bypotentiometric titration with silver nitrate solution using a sulfide-specificelectrode; the sulfide standard should be at least 90 % pure.10. Procedure10.1 Disintegrate the sample in the blender
30、with 75 mL ofwater and transfer the test specimen from the disintegratorquantitatively to the 500-mL reaction flask using additionalaliquots of 5 mL of water to assist in the transfer. Add2gofaluminum foil (or one aluminum foil weighing dish) which hasbeen cut into12-in. (12.7-mm) squares and comple
31、te theassembly of the reaction apparatus.10.2 Precipitation of Cadmium Sulfide:6“Reagent Chemicals, American Chemical Society Specifications,” Am. Chemi-cal Soc., Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see “Reagent Chemicals and Standar
32、ds,” by JosephRosin, D. Van Nostrand Co., Inc., New York, NY, and the “United StatesPharmacopeia.”FIG. 1 Reaction Apparatus (Quantitative Determination).D 984 97 (2002)210.2.1 Measure 10 mL of the concentrated H3PO4(sp gr1.69) into the dropping funnel and 75 mL of the cadmiumhydroxide absorption sus
33、pension (which is swirled beforepouring and should include some solids) into the darkened100-mL volumetric collecting flask. Start bubbling the nitrogenat the rate of about 5 bubbles per second, taking care to ensurethat there are no leaks. Use top quality sulfur-free stopcockgrease at the joints an
34、d if necessary tie the joints with clampsor rubber bands. After the nitrogen has been adjusted submergethe delivery tube into the absorption suspension in the 100-mLvolumetric flask and put the ice bath in place, taking care toassure that the tip is to the bottom of the flask (that is,submerged as d
35、eeply as possible).10.2.2 Add the 10 mL of concentrated H3PO4from thedropping funnel. Leave a small amount of acid in the tip, closethe stopcock on the funnel, and start heating the mixture to aboil. Take care that the absorption solution does not back up inthe delivery tube while the mixture is hea
36、ting. It may benecessary to adjust the nitrogen flow to prevent this.10.2.3 Discontinue heating after 45 min, remove the volu-metric flask together with the side-arm adapter by dislodging itat the condenser, and stop the nitrogen flow. Keep the adaptertogether with the flask until the amine reagent
37、is added in thecolor development step because the cadmium sulfide oftenhangs up in the tube tip. The sample should not be stored in thismanner for more than 1 h.10.3 Preparation of Calibration StandardsAdd 75 mL ofthe cadmium hydroxide absorption suspension to each of five100-mL darkened volumetric
38、flasks and place in the constanttemperature bath (20 to 25C) if available. Pipet 1, 2, 5, and 10mL, respectively, of the sodium sulfide standard workingsolution into four of the volumetric flasks. Prepare each timethe analysis is performed. Swirl gently but adequately. Theflask containing no sulfide
39、 solution is the reagent blank. Thestandards contain 2, 4, 10, and 20 g of sulfur per 100 mL.NOTE 3The “blow-out” pipets are used to pipet the sodium sulfideworking solution aliquots. They are immersed into the absorption solu-tions and allowed to drain slowly while the tips are below the surface.Wh
40、en drainage is complete, gently blow out the last drops while stillimmersed and then remove from the flask.10.4 Color Development and Read-Out:10.4.1 To the test specimen, reagent blank, and calibrationstandard 100-mL volumetric flasks, add 2 mL of the diluteamine solution. Allow the dense amine sol
41、ution to flow downthe side of the flask to the bottom of the absorption solution.Stopper the flask and swirl gently but adequately a few timeswithout shaking (heat will be regenerated). Immediately add 10drops of the ferric chloride solution and shake vigorously toreact any hydrogen sulfide (H2S) wh
42、ich may have come out ofthe solution. Dilute each solution to the mark with water, mixwell, and allow to stand for at least 20 min. The colordevelopment should be conducted in the dark and if possible at20 to 25C by means of the constant-temperature bath or byany other comparable means available.10.
43、4.2 Read the maximum absorbance at the peak at or near670 nm, using water as the reference. Subtract the absorbanceof the reagent blank (as the correction) from the calibrationstandards and the test specimen. Plot the corrected absorbanceof the calibrated standards versus micrograms of sulfur presen
44、tand draw the best straight line passing through zero. (The slopeshould be about 0.005 to 0.010 absorbance units per 1 g ofsulfur per 10 nm of path length.) Read the amount of reduciblesulfur, in micrograms, in each specimen directly from the chartbased on its net absorbance.11. Calculation11.1 Calc
45、ulate the parts per million of reducible sulfur in thespecimen, P, as follows:P 5 R/W (1)where:R = reducible sulfur from chart, g, andW = weight of specimen, g.11.2 Calculate the percent reducible sulfur, P8, as follows:P8 5 P3 0.0001 (2)12. Report12.1 Report the following information:12.1.1 Amount
46、of reducible sulfur as a percentage by weightof the moisture-free paper to two significant figures, and12.1.2 Individual values for each specimen which agree towithin 650 % relative average deviation, as well as reportingthe average for the three determinations.13. Precision and Bias13.1 Precision:1
47、3.1.1 The following estimates of precision are based onlimited experience: a within-laboratory study of three sets of alinerboard sample and a round-robin among three laboratorieson five different linerboard samples.13.1.2 Repeatability (Within Laboratory)0.91 ppm reduc-ible sulfur (11%).13.1.3 Comp
48、arability (Between Materials)Not known.13.1.4 Reproducibility (Between Laboratories)24%.13.2 BiasSince there is no accepted reference materialsuitable for determining the bias for the procedure in this testmethod, bias has not been determined.METHOD BSEMIQUANTITATIVE MEASUREMENT14. Apparatus14.1 Rea
49、ction ApparatusEssentially the same as thequantitative method (8.1), except that the side arm adapter andthe absorption apparatus are replaced by a glass tube withsuitable ground-glass joint (Fig. 2). The tube should be 100mm in length with flanged heads ground flat on both sides anda means of clamping the flanges together with two disks offilter paper between them. The outermost paper disk is impreg-nated with lead acetate.14.2 Other EquipmentSame as 8.5, and in addition a buretor pipet graduated in 0.1-mL divisions.15. Reagents and Materials1
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