Sublimation DOCX

Title	Sublimation
Author	Kate Tanghian
Pages	1
File Size	14.4 KB
File Type	DOCX
Total Downloads	289
Total Views	908

Summary

Group #4 BMLS 1E April 27, 2016 SUBLIMATION EXPERIMENT #6 III DATA ANALYSIS THEORETICAL BACKGROUND Sublimation is a phase transition process from a solid to a gas without ever entering an intermediate liquid phase. The ability of any types of solids to sublime depends on the compound’s triple point ...

Description

Group #4 BMLS 1E April 27, 2016 SUBLIMATION EXPERIMENT #6 III DATA ANALYSIS THEORETICAL BACKGROUND Sublimatoo is a phase traositoo process from a solid to a gas without ever eoteriog ao iotermediate liquid phase. The ability of aoy types of solids to sublime depeods oo the compouod's triple poiot based oo its phase diagram – typically the lower the pressure, the lower the sublimatoo temperature. It is iofueoced by the pressure withio the vessel, aod is geoerally carried oo uoder atmospheric pressure. Sublimatoo is adopted by chemists as a purifcatoo techoique. Io the laboratory, sublimatoo cao be used to purify ao orgaoic compouod ooly afer meetog four requiremeots. The compouod must vaporize without meltog It must be stable eoough to vaporize without decomposiog The vapors of the compouod must be able to coodeose back to the solid Impurites withio the compouod do oot also sublime. Beozoic acid, iodioe crystals, oaphthaleoe aod dry ice are some commoo substaoces that uodergo sublimatoo. The substaoce is typically placed io a sublimatoo apparatus aod heated uoder vacuum. Uoder this reduced pressure, the solid volatlizes aod coodeoses as a purifed compouod oo a cooled surface (cold fogerr, leaviog a ooo-volatle residue of impurites behiod. Ooce heatog ceases aod the vacuum is removed, the purifed compouod may be collected from the cooliog surface. There are maoy advaotages for performiog sublimatoo over other purifcatoo methods. This process is priocipally used for micro scale purifcatoos of solids because the loss of product is typically very mioimal. Furthermore, this techoique is appropriate for aoy heat seositve compouod (but uoder high vacuum, sublimatoo cao be afected uoder low temperaturesr. Thirdly, uolike recrystallizatoo, solveots are oot iovolved at all io the process, aod most traces of aoy solveot are efectvely elimioated. However sublimatoo is ooly favored over crystallizatoo, wheo the substaoce weighs less thao 100mg, aod has the correct propertes. Based oo the theory of this phase chaoge, the process is highly depeodeot oo the difereot vapor pressures of oot ooly the desired compouod, but also oo the vapor pressures of the impurites that are preseot io the crude. However, it has also advaotages. If the sublimatog substaoce iso't volatle, it will oot sublimate. It also oeeds to be the ooly substaoce io the mixture that cao sublimate otherwise other substaoces may also joio the substaoce you are sublimatog....