1、Designation:D 4278 02Standard Practice forWet Ashing Procedure for Preparing Wood Samples forInorganic Chemical Analysis1This standard is issued under the fixed designation D 4278;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the y
2、ear 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 This practice consists of a procedure for decompositionof wood as an initial step for analysis for the constituents
3、arsenic,chromium,copper,phosphate,and zinc,all of whichmay then be analyzed in accordance with Test MethodsD 1326,D 1627,D 1628 and D 5584.1.2 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 es
4、tablish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.Specific precau-tionary statements are given in Section 7.2.Referenced Documents2.1 ASTM Standards:D 1326 Methods for Chemical Analysis of AmmoniacalCopper Arsenate2D 1627 Methods
5、 for Chemical Analysis of Acid CopperChromate2D 1628 Test Methods for Chemical Analysis of ChromatedCopper Arsenate2D 5584 Test Methods for Chemical Analysis of Ammonia-cal Copper Quat,Type B(ACQ-B)23.Summary of Test Method3.1 A small(up to 5 g)sample of chopped or ground wood(usually treated)is oxi
6、dized and solubilized by an initialdigestion in hot concentrated nitric acid.This is followed byfurther digestion after the addition of a solution of aqueousperchloric acid in concentrated sulfuric acid.The cooledsolution of metal salts is then diluted and is suitable foranalysis by the appropriate
7、method.4.Significance and Use4.1 Many wood preservatives consist of inorganic materials.These materials are often preferably analyzed in dilute aqueoussolutions in the absence of organic matter.This practiceprovides a means for the preparation of a dilute aqueoussolution of the inorganic materials w
8、hich are in wood bysimultaneously decomposing the wood sample and solubilizingthe inorganic materials.The aqueous solution may then beanalyzed for its inorganic constituents by applicableASTM testmethods.5.Apparatus5.1 For each digestion to be run simultaneously,the follow-ing apparatus is required:
9、5.1.1 Kjeldahl Flask,800 mL,with 24/40 ground glass top.5.1.2 Ground Glass Stopper,24/40.5.1.3 Kjeldahl Flask Heater,rheostat-controlled.5.1.4 Tubing,38-in.TFE-fluorocarbon.5.1.5 Glass Beads.5.2 For each group of digestions,the following apparatus isrequired:5.2.1 Tube Connectors,Y-form,glass,38-in.
10、5.2.2 Aspirator,TFE-fluorocarbon.5.3 The apparatus is assembled as shown schematically inFig.1.Up to six samples can be handled with a single aspirator.During digestion,clamps may be used on the tubing to balancethe rate of aspiration between flasks.It may occasionally benecessary to enlarge the asp
11、irator hole to about116in.tooptimize aspiration,either because of extraneous plastic in anew aspirator,or because of build-up during use.5.4 A syringe is also required for the introduction of acidduring digestion.Care should be taken to keep the bulb free ofacid oxidant and the syringe should be rin
12、sed after use.5.5 Grinding Mill.6.Reagents6.1 Nitric Acid,concentrated(sp gr 1.42).6.2 Sulfuric Acid,concentrated(sp gr 1.84).6.3 Perchloric Acid,70%.6.4 Acid OxidantAdd 185 volumes of perchloric acid(70%)to 100 volumes of distilled water and then add slowlywith mixing 270 volumes of concentrated su
13、lfuric acid.1This test method is under the jurisdiction of ASTM Committee D07 on Woodand is the direct responsibility of Subcommittee D07.06 on Wood Preservatives.Current edition approved Sept.10,2002.Published November 2002.Originallypublished as D 4278 83.Last previous edition D 4278 95.2Annual Bo
14、ok of ASTM Standards,Vol 04.10.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.7.Safety Precautions7.1 Although several thousand wood analyses have beencarried out by this method without accident,the improper orcareless use of perchloric
15、acid has caused violent and danger-ous explosions.Careful adherence to all directions is essential.For the safe digestion of wood,two essential precautions arevital:(1)the sample should be mixed with nitric acid andfurther reagents should be withheld until the evolution ofbrown fumes has subsided;(2
16、)perchloric acid should bediluted with sulfuric acid to form the acid-oxidant before it isadded to the digestion mixture.Once the digestion has started,addition of wood,or contact with other organic matter,shouldbe avoided.If such contact should inadvertently occur,floodthe digestion flask with large amounts of cold water immedi-ately.7.2 The following general rules apply to the use of perchlo-ric acid:Virtually all known explosions may be attributed tocontact of raw organic matter or other easi
