ASTM_E_118_-_89_1996.pdf

Designation:E 118 89(Reapproved 1996)Standard Test Methods forChemical Analysis of Copper-Chromium Alloys1This standard is issued under the fixed designation E 118;the number immediately following the designation 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 procedures for the chemicalanalysis of chromium-copper alloys having chemical compo-sitions within the following limits:Copper,%98 and overChromium,%0.6 to 1.2Silicon,%0 to 0.10Iron,%0 to 0.101.2 The analytical procedures appear in the following order:SectionsCopper by the Electrolytic Method8-11Chromium by the Dichromate(Potentiometric)Method12-15Silicon by the Perchloric Acid Dehydration Method162.Referenced Documents2.1 ASTM Standards:E 29 Practice for Using Significant Digits in Test Data toDetermine Conformance With Specifications2E 50 Practices for Apparatus,Reagents,and Safety Precau-tions for Chemical Analysis of Metals3E 54 Test Methods for Chemical Analysis of SpecialBrasses and Bronzes3E 55 Practice for Sampling Wrought Nonferrous Metals andAlloys for Determination of Chemical Composition3E 60 Practice for Photometric and SpectrophotometricMethods for Chemical Analysis of Metals3E 62 Test Methods for Chemical Analysis of Copper andCopper Alloys(Photometric Methods)33.Significance and Use3.1 These test methods for the chemical analysis of metalsand alloys are primarily intended to test such materials forcompliance with compositional specifications.It is assumedthat all who use these test methods will be trained analystscapable of performing common laboratory procedures skill-fully and safely.It is expected that work will be performed ina properly equipped laboratory.4.Apparatus,Reagents,and Photometric Practice4.1 Apparatus and reagents required for each determinationare listed in separate sections preceding the procedure.Theapparatus,standard solutions,and certain other reagents usedin more than one procedure are referred to by number and shallconform to the requirements prescribed in Practices E 50,except that photometers shall conform to the requirementsprescribed in Practice E 60.4.2 Photometric practice prescribed in these test methodsshall conform to Practice E 60.5.Hazards5.1 For hazards to be observed in these test methods,reference shall be made to Practices E 50.6.Sampling6.1 Wrought products shall be sampled in accordance withPractice E 55.7.Rounding Calculated Values7.1 Calculated values shall be rounded to the desired num-ber of places in accordance with the rounding method given in3.4 and 3.5 of Practice E 29.COPPER BY THE ELECTROLYTIC TESTMETHOD8.Apparatus8.1 Electrodes for ElectroanalysisApparatus No.9.9.Reagents9.1 Sulfuric-Nitric Acid MixtureAdd slowly,while stir-ring,500 mLof H2SO4to 1700 mLof water.Cool,and add 300mL of HNO3.9.2 Hydrogen Peroxide(3%).10.Procedure10.1 Transfer 2.0000 g of the sample to a 250-mL electroly-sis beaker,cover,and dissolve in 60 mL of the H2SO4-HNO3mixture.Allow the beaker to remain on a steam bath untilsolution of the sample is complete,add a few drops of HF and1These test methods are under the jurisdiction of ASTM Committee E-1 onAnalytical Chemistry for Metals,Ores,and Related Materials and are the directresponsibility of Subcommittee E01.05 on Cu,Pb,Zn,Cd,Sn,Be,their Alloys andRelated Metals.Current edition approved Oct.27,1989.Published January 1990.Originallypublished as E 118 56 T.Last previous edition E 118 60(1978).2Annual Book of ASTM Standards,Vol 14.02.3Annual Book of ASTM Standards,Vol 03.05.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.carefully evaporate to fumes to decompose the sample com-pletely.Cool,dilute with water,add 3 mL of HNO3,and warmto dissolve all soluble salts.Wash down the cover glass andsides of the beaker and dilute to about 150 mL with water.10.2 Insert the electrodes into the solution with a pair ofsplit watch glasses,and electrolyze overnight at a currentdensity of 0.5 A/dm2or for 212h at a current density of 4A/dm2(Note 1).The more rapid procedure requires the use ofgauze cathodes.When the solution is colorless,wash down thecover glasses,electrodes,and the s ides of the beaker,andcontinue the electrolysis until deposition of the copper iscomplete,as indicated by failure to plate on a new surfacewhen the level of the solution is raised(Note 2).NOTE1When agitation of the electrolyte is permissible in order todecrease the time of deposition,one of the types of rotating forms ofelectrodes generally available may be employed.NOTE2If the electrolyte is not to be used for subsequent determina-tions,remove a few drops of the solution,place on a porcelain spot plate,and treat with saturated H2S solution.Continue electrolysis until no CuSprecipitate is observed.10.3 When deposi