File:Air-free sublimation.png
Summary
Air-free sublimation
Apparatus
a = Rubber cone (typically used to form a vacuum seal in a <a href="//commons.wikimedia.org/w/index.php?title=B%C3%BCchner_flask&action=edit&redlink=1" class="new" title="Büchner flask (page does not exist)">Büchner flask</a> filtration) which is selected so as to fit snugly around the neck of the <a href="//commons.wikimedia.org/w/index.php?title=Schlenk_tube&action=edit&redlink=1" class="new" title="Schlenk tube (page does not exist)">Schlenk tube</a>
b = <a href="//commons.wikimedia.org/w/index.php?title=Schlenk_tube&action=edit&redlink=1" class="new" title="Schlenk tube (page does not exist)">Schlenk tube</a>
c = Gas/vacuum inlet
d = Teflon tap (or stopcock)
e = Syringe
Method steps
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
Licensing
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File history
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 05:35, 13 January 2017 | | 800 × 475 (31 KB) | 127.0.0.1 (talk) | <p>Air-free sublimation </p> <p><u>Apparatus</u> </p> <p><b>a</b> = Rubber cone (typically used to form a vacuum seal in a <a href="//commons.wikimedia.org/w/index.php?title=B%C3%BCchner_flask&action=edit&redlink=1" class="new" title="Büchner flask (page does not exist)">Büchner flask</a> filtration) which is selected so as to fit snugly around the neck of the <a href="//commons.wikimedia.org/w/index.php?title=Schlenk_tube&action=edit&redlink=1" class="new" title="Schlenk tube (page does not exist)">Schlenk tube</a> </p> <p><b>b</b> = <a href="//commons.wikimedia.org/w/index.php?title=Schlenk_tube&action=edit&redlink=1" class="new" title="Schlenk tube (page does not exist)">Schlenk tube</a> </p> <p><b>c</b> = Gas/vacuum inlet </p> <p><b>d</b> = Teflon tap (or stopcock) </p> <p><b>e</b> = Syringe </p> <p><u>Method steps</u> </p> <p><b>1</b> = 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). </p> <p><b>2</b> = 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). </p> <p><b>3</b> = 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. </p> <p><b>4</b> = Solvent (blue) is inserted via syringe to dissolve the residue (green/brown), taking care to avoid washing off the sublimed solid (purple). </p> <p><b>5</b> = Residue solution is then removed by syringe (green/brown) (Steps <b>4</b> and <b>5</b> can be repeated as required). </p> <p><b>6</b> = Purified sublimed solid (purple) is washed off the neck of the flask with fresh solvent (blue) via a syringe. </p> <p>(In steps <b>3</b> to <b>6</b> the flask is held under an atmosphere of an inert gas via Schlenk tube side arm). </p> <p><b>7</b> = Solvent is removed under vacuum to give the purified sublimed solid (dark purple). </p> <p>Steps <b>6</b> and <b>7</b> are not essential </p> |
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