How to Use a Side-Draw Distillation Column
A side-draw distillation column is a common laboratory apparatus which allows the fractional distillation of mixed compounds using a single column. By condensing the vapor of a boiling compound at multiple points along the column, a distillation column produces nearly pure samples of the chemical with the lowest boiling point in the compound. It is best used when distilling compounds whose components have widely differing boiling points. Compounds whose components have similar boiling points are more easily distilled using a two-column setup. A basic side-draw distillation column consists of a boiling chamber, a column packed with an inert sponge, such as glass beads or copper wool and a side-draw distilling head.
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Things You'll Need
- Distillation column
- Packing material
- Round-bottomed flask
- Ring stand
- Three-pronged clamp
- Glassware grease
- Rubber glassware joints
- Side-draw distilling head
- Thermometer adapter
- Thermometer
- Heat source
- Graduated cylinder or flask
Instructions
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Assembling the Column
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1
Fill the column with packing material. Choose a packing material that will not react chemically with any component of the solution you wish to distill. If you are using a compressible packing material, such as steel or copper wool, do not pack it so tightly that vapor cannot pass freely through the material.
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2
Fill a round-bottomed flask halfway full of the compound you wish to distill. Attach it to a ring stand using a three-pronged clamp.
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3
Grease a pair of rubber glassware joints and attach them securely to the top and bottom of the cylinder. Attach the bottom of the column to the mouth of the round-bottomed flask. The bottom of the column is the end with the narrow mouth or glass protrusions to hold the packing material in place.
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4
Attach a side-draw distillation head to the top of the column. Attach a thermometer adapter to the top of the distillation head. Grease a closed-end thermometer and insert it into the thermometer adapter. The bulb of the thermometer should be level with the side-draw nozzle.
Distillation Process
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5
Place a graduated cylinder or flask underneath the nozzle of the distillation head.
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6
Place a heat source underneath the round-bottomed flask. For non-volatile compounds with a high boiling point, a Bunsen burner may be used. For volatile compounds or those with a low boiling point, an electrically heated sand bath should be used instead. Apply heat greater than the lowest boiling point in the compound but lower than the boiling points of the other components.
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7
Monitor the thermometer until the temperature rises suddenly, then stabilizes. This represents the boiling point of the compound you are attempting to distill. If the temperature rises steadily and then stabilizes, apply more heat. If the temperature resumes rising after the initial sudden rise and stabilization, reduce heat slightly.
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8
Continue boiling the liquid until it has almost all boiled away. Remove the heat source and the collection flask. Replace it with another flask to catch any remaining drops from the apparatus. Once the heat source has been removed, any further output will not be pure distillate and should be discarded or reused for future distillations.
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Tips & Warnings
Wrapping the cylinder loosely in aluminum foil can preserve even heating in cold or drafty labs. Dropping a boiling stone into the round-bottomed flask or stirring the contents with a magnetic stirrer throughout the boiling process can help speed the rate of boiling and shorten the distillation time. Check your rubber joints for fraying or etching before assembling your distillation column. Damaged joints can leak chemical vapor, resulting in a loss of product and a possible inhalation hazard.
Always wear protective clothing when heating chemical compounds. This includes heat- and chemical-resistant gloves and goggles and may include a respirator or vent hood. Read the material safety data sheets (MSDS) for all chemicals involved in a distillation before proceeding. Check your glassware for cracks or flaws before assembling your distillation column. Cracked glassware can explode under the heat and pressure of distillation.
