ASTM_E_104_-_02_2012.pdf

Designation:E10402(Reapproved 2012)Standard Practice forMaintaining Constant Relative Humidity by Means ofAqueous Solutions1This standard is issued under the fixed designation E104;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.This standard has been approved for use by agencies of the Department of Defense.1.Scope1.1 This practice describes one method for generating con-stant relative humidity(rh)environments in relatively smallcontainers.1.2 This practice is applicable for obtaining constant rela-tive humidities ranging from dryness to near saturation attemperatures spanning from 0 to 50C.1.3 This practice is applicable for closed systems such asenvironmental conditioning containers and for the calibrationof hygrometers.1.4 This practice is not recommended for the generation ofcontinuous(flowing)streams of constant humidity unlessprecautionary criteria are followed to ensure source stability.(See Section 9.)1.5 CautionSaturated salt solutions are extremelycorrosive,and care should be taken in their preparation andhandling.There is also the possibility of corrosive vapors in theatmospheres over the saturated salt solutions.21.6 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.For more specificsafety precautionary information see 1.5 and 10.1.2.Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterD1356 Terminology Relating to Sampling and Analysis ofAtmospheres2.2 Other Document:DIN50008“Konstantklimate uber waesserigen Loseungen”(Constant Climates Over Aqueous Solutions).Part 1:Saturated Salt and Glycerol Solutions.43.Terminology3.1 non-hygroscopic materialmaterial which neither ab-sorbs nor retains water vapor.3.2 For definitions of other terms used in this practice referto Terminology D1356.4.Summary of Practice4.1 Standard value relative humidity environments are gen-erated using selected aqueous saturated salt solutions.5.Significance and Use5.1 Standard value relative humidity environments are im-portant for conditioning materials in shelf-life studies or in thetesting of mechanical properties such as dimensional stabilityand strength.Relative humidity is also an important operatingvariable for the calibration of many species of measuringinstruments.6.Interferences6.1 Temperature regulation of any solution-head space en-vironment to 60.1C is essential for realizing generatedrelative humidity values within 60.5%(expected).6.2 Some aqueous saturated salt solutions change composi-tion following preparation by hydrolysis or by reaction withenvironmental components(for example,carbon dioxide ab-sorption by alkaline materials).These solutions should befreshly prepared on each occasion of use.7.Apparatus7.1 ContainerThe container,including a cover or lidwhich can be secured airtight,should be made of corrosion1This practice is under the jurisdiction ofASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.11 on Meteorology.Current edition approved April 1,2012.Published July 2012.Originallyapproved in 1951.Last previous edition approved in 2007 as E104-02(2007).DOI:10.1520/E0104-02R12.2Opila,R.,Jr.,Weschler,C.J.,and Schubert,R.,“Acidic Vapors AboveSaturated Salt Solutions Commonly Used for Control of Humidity,”IEEE Trans.Components,Hybrids and Manufacturing Technology,Vol 12,No.1,March 1989,pp.114120.3For 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.4Published by Deutsches Institut fr Normung,4-10 Burggrzfenstrasse Postfach1107,D-1000 Berlin,Federal Republic of Germany.Also available from ANSIPublication Office,New York,NY.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 resistant,non-hygroscopic material such as glass.A metal orplastic container is acceptable if the solution is retained in adish or tray made of appropriate material.Refer also to 9.2 forsize restrictions.8.Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused for preparation of all standard solutions.Unless otherwiseindicated,it is intended that all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society where such specifications areavailable.5Other grades may be used,provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the d