ASTM_B_712_-_93_2012.pdf

Designation:B71293(Reapproved 2012)Standard Guide forDetermination of Sodium and Potassium Content For Silver-Cadmium Oxide Contact Materials1This standard is issued under the fixed designation B712;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide describes procedures for use in conductinganalysis of silver-cadmium oxide materials for sodium andpotassium content.The exact methods for the performance ofthis testing are not stated since many different procedures areequally applicable.This guide points out specific proceduresfor decreasing the chance of recognized potential errors andspecifies methods for increasing the sensitivity of the testing.1.2 This standard may involve hazardous materials,operations,and equipment.This standard does not purport toaddress all of the safety concerns,if any,associated with itsuse.It is the responsibility of the user this standard to becomefamiliar with all hazards including those identified in theappropriate Material Safety Data Sheet(MSDS)for thisproduct/material as provided by the manufacturer,to establishappropriate safety and health practices,and determine theapplicability of regulatory limitations prior to use.For specificprecautions see Sections 4 and 6.1.3 Whoever uses this standard should consult the MaterialSafety Data Sheet concerning the products involved.2.Referenced Documents2.1 ASTM Standards:2E50 Practices for Apparatus,Reagents,and Safety Consid-erations for Chemical Analysis of Metals,Ores,andRelated MaterialsE663 Practice for Flame Atomic Absorption Analysis(With-drawn 1997)32.2 Other Document:Operation Guide for Chemical Analysis of Metals and MetalBearing Ores by Atomic Absorption Spectrophotometry43.Significance and Use3.1 This guide is recommended for use in analyzing thesodium and potassium content of silver-cadmium oxide mate-rials and is meant to be used in conjunction with standardmethods of atomic absorption spectroscopy.The recommendedprocedures cite methods for minimizing extraneous sodiumand potassium contamination through use of specific handlingprocedures and shorter sample preparation methods.This guidealso recommends procedures that prevent the formation ofnonstable and potentially hazardous silver-acetylene com-pounds.4.Precautions4.1 Since silver nitrate reacts with acetylene to form silveracetylide,the guide recommends either alternative flames toairacetylene or the removal of silver from solution.Silveracetylide is unstable and may explode violently upon beingdisturbed.5.Sampling5.1 Handle the sample so as to avoid contamination bysodium and potassium;avoid contact with hands.6.Procedures6.1 First clean the sample in nitric acid and distilled ordeionized water to remove extraneous surface contamination.Test powder samples as received.Then store the samples insuch a manner as to minimize contamination.6.2 Use a sample size of approximately 2 g or more for eachtest.6.3 Handle the samples with gloves and utensils,never withbare hands.6.4 The use of TFE-fluorocarbon or other suitable substi-tutes for glassware is recommended.If glass is used,aged glass1This guide is under the jurisdiction of ASTM Committee B02 on NonferrousMetals and Alloys and is the direct responsibility of Subcommittee B02.05 onPrecious Metals and Electrical Contact Materials.Current edition approved May 1,2012.Published May 2012.Originallyapproved in 1982.Last previous edition approved in 2006 as B712 93(2006).DOI:10.1520/B0712-93R12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.41982 Annual Book of ASTM Standards,Part 12(see Related MaterialsSection).Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesNOTICE:This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International(www.astm.org)for the latest information1 rather than new glass is recommended.Clean the glasswarewith ammonia and rinse with deionized water.Avoid the use ofdetergents.6.5 Calibrate the instrument and determine the optimumcalibration-solution concentration in accordance with PracticeE663 and other standards as cited in Section 2.6.6 Fully dissolve the sample in a nitric acid solution inaccordance with standard procedures and concentrations rec-ommended for the atomic absorption procedures and instru-ments used.Also prepare a reagent blank.6.7 An air-propane or air-hydrogen flame is recommendedrather than air-acetylene in order to prevent the formation ofsilver acetylide.(Wa