. ---, -------, -------, ------,

FIG.1(a)Desorptioncurvesofn-butanolfromsilicagelSi-100;(b)temperaturevs. time(solidline,quasi-isothermalprogram;dottedline,linearprogram).(Reprinted fromRef.38withpermissionfromElsevierScience.)

!:l.m=f(T).InFig.1thedependenceoftemperatureagainsttimeforthesame desorptionprocessisalsoshown.Forillustrativepurpoes,thedottedcurvesrepresenttheresultsobtainedbyapplyingadynamic,linearheatingprogramwithcontinuouslyincreasingtemperature.Inthiscasethecharacteristicpointsonthe desorptioncurveconnectedwiththetexturalpropertiesofthesoliddisappear. TwomainconclusionscanbedrawnfromFig.1.Thefirst,andmostobvious,is thatthetotaltimeofanalysisdependsontheheatingmode.Thesecondisthatthe linearheatingmodeisinadequateintheinvestigationsoftheporosity.SegmentIof thiscurverepresentsthebulkliquidoutsidetheporestructureoftheadsorbent. Intensiveevaporationatthisstageoftheprocesstakesplaceattheboilingpointof theliquid(perpendicularsegment).Whenthefirststageiscompleted,thetemperatureincreasesataheatingratelowerthanthatduringtheinitialheatingprogram andstartsthedesorptionfrompores.SegmentIIcorrespondstothecapillarycondensedliquidwithintheporestogetherwiththeadsorbedfilmonthewallsof poresandis,therefore,ameasureofthetotalporevolume.Thesteepestpartofthe curveabovetheboilingpointoftheliquidcorrespondstothedesorptionfrom poresofthegreatestpartofthetotalporevolume.