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| Keywords: Air-free sublimation.png Air-free sublimation <U>Apparatus</U> a Rubber cone typically used to form a vacuum seal in a Büchner flask filtration which is selected so as to fit snugly around the neck of the Schlenk tube b Schlenk tube c Gas/vacuum inlet d Teflon tap or stopcock e Syringe <u>Method steps</u> 1 Impure solid to sublime brown is placed in a Schlenk tube avoiding contaminating the sides of the tube e g by careful evaporation from a solution containing the brown solid 2 Rubber cone black is pushed near top of the Schlenk tube forming a tight seal around flask and filled with a coolant such as dry ice/acetone blue/white to cool the neck of the Schlenk tube The bottom of the Schlenk tube is heated red shading under vacuum blue arrow so that the impure solid brown sublimes as a pure solid purple at the cooled neck area blue shading 3 After sublimation the cooling-cone black is removed leaving the concentrated impurity as a residue dark brown in the bottom of the flask and the purified sublimed solid purple at the neck of the Schlenk tube 4 Solvent blue is inserted via syringe to dissolve the residue green/brown taking care to avoid washing off the sublimed solid purple 5 Residue solution is then removed by syringe green/brown Steps 4 and 5 can be repeated as required 6 Purified sublimed solid purple is washed off the neck of the flask with fresh solvent blue via a syringe In steps 3 to 6 the flask is held under an atmosphere of an inert gas via Schlenk tube side arm 7 Solvent is removed under vacuum to give the purified sublimed solid dark purple Steps 6 and 7 are not essential Own Quantockgoblin Schlenk flasks Sublimation | ||||
