ASTM_D_5032_-_11.pdf

Designation:D503211Standard Practice forMaintaining Constant Relative Humidity by Means ofAqueous Glycerin Solutions1This standard is issued under the fixed designation D5032;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 practice describes a method for obtaining constantrelative humidity ranging from 30 to 98%at temperaturesranging from 0 to 70C in relatively small containers by meansof an aqueous glycerin solution.1.2 This practice is applicable for closed systems such asenvironmental conditioning containers.1.3 This practice is not recommended for the generation ofcontinuous(flowing)streams of constant humidity unlessprecautionary criteria are followed to ensure source stability.1.4 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.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD4023 Terminology Relating to Humidity Measurements(Withdrawn 2002)3D6054 Practice for Conditioning Electrical Insulating Mate-rials for Testing(Withdrawn 2012)3E104 Practice for Maintaining Constant Relative Humidityby Means of Aqueous Solutions2.2 Other Documents:DIN50008 Constant Climates over Aqueous Solutions4Part 1:Saturated Salt and Glycerol SolutionsPart 2:Sulfuric Acid Solutions(1981)3.Summary of Practice3.1 Controlled relative humidity environments are gener-ated using mixtures of glycerin and water.3.2 Practice E104 contains methods for maintaining con-stant relative humidity environments using aqueous saturatedsalt solutions or various strength sulfuric acid-water systems.4.Significance and Use4.1 Controlled relative humidity environments are impor-tant for conditioning materials for shelf-life studies or forinvestigating the change in physical or dielectric propertiesafter exposure.4.2 The use of aqueous-glycerin solutions reduces the pos-sibility of contamination of the materials or corrosion ofelectrode systems which would be more likely to result fromsaturated salt or acid water solutions.4.3 Applicable material specifications should state the ex-posure conditions,including time,temperature and relativehumidity that a material should be subjected to before subse-quent testing.Typical conditions are given in Practice D618 orD6054.5.Apparatus5.1 Container,airtight,of a material not acted upon bycopper sulfate(or with the glycerin solution contained in a traymade of a material not acted upon by copper sulfate).5.2 Refract meter,covering the range of 1.33 to 1.47(sodium)with an accuracy of 0.0003.6.Glycerin Solution6.1 Use a good industrial grade of glycerin(“high gravity”and“dynamite”grades have been found to be satisfactory)indistilled water.Calculate the concentration in terms of therefractive index,(R),at 25C for the desired relative humidityat any temperature between 0 and 70C as follows:R 5=1001A!21A22H1A!22 A!1715.311.3333(1)1This practice is under the jurisdiction of ASTM Committee D09 on Electricaland Electronic Insulating Materials and is the direct responsibility of SubcommitteeD09.12 on Electrical Tests.Current edition approved Aug.1,2011.Published September 2011.Originallyapproved in 1990.Last previous edition approved in 2003 as D5032 97(2003).DOI:10.1520/D5032-11.2For 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.4Available from Deutsches Institut fur Normung,4-10 BurggrenzenstrassePostfach 1107,D-1000 Berlin,Germany.Also available from American NationalStandards Institute,25 W.43rd St.,4th Floor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 where:T=temperature of the solution,C,A=25.60 0.1950T+0.0008T2,andH=relative humidity,percent.6.1.1 This will give the desired relative humidity with anaccuracy of 60.2%at a constant temperature of 25C.At otherconstant temperatures,the error,if any,may increase with thedeviation of the temperature from 25C.The relative humidityvalues at 0,25,50 and 70C for a number of refractive indexvalues are given in Table 1.Obtain the refractive index forintermediate values of relative humidity and temperature byplotting curves from the values in the table or by calculatingfrom the above formula.6.2 To prevent fungus growth in the solution,add about0.1%by weight of copper sulfate to the glycerin solution.Themost