Body

245 * Lab #2
Simple Distillation

This lab includes the physical setup of a simple distillation apparatus. The glassware that you are responsible for is very expensive, so be sure to support it well. You will be using ring stands, 3-prong clamps, blue glassware clips and vacuum grease to assemble the apparatus. Be very careful. You will also be using a heating mantle for the distillation. The heating mantles we will be using have the shape to accept 50 to 500 mL round bottom flasks. The blue heating mantles have the power source built in to the unit. The mantles can be directly attached to the ring stand via the support on the back of the mantle. This aids in setting up the distillation glassware. The flask must be as low in the heating mantle as possible to be in contact with the heat source. You may have to clamp the 3-way adapter.

Whenever you do a distillation of an organic liquid, you want to be sure that your glassware has been cleaned and dried.

Soap and acetone are available to you in the future for cleaning the glassware. If you are going to be distilling a non-aqueous reagent (you are not doing this today) you want to make sure that the flask is completely dried. Use a very small amount of acetone for this task. Be sure to dispose of the waste acetone in the correct waste jug. Do not put it into the sink. As you perform the distillation you want to understand what you are seeing. You should know from your prelab the different parts of the distillation apparatus. When heat is applied to the system, the chemical in the still pot will absorb this heat until it reaches its boiling point. The temperature at which the chemical attains a vapor pressure equal to the pressure that the system is exposed to. This is usually atmospheric pressure, but it can be lowered by use of the vacuum adapter. As the chemical is changed to vapor it travels from the still pot to the stillhead. The stillhead area is where the thermometer is set to read the temperature. This is also the area just before the condenser. When you begin to see the vapor condensed in the column and dripping into the receiving flask, then you want to read the temperature. This temperature represents the boiling point of the condensed vapor you are collecting in the receiving flask. As long as that temperature remains constant, you can be sure that you are receiving the same chemical. If, though, the distillate production slows down and stops and the temperature at the stillhead begins to rise, or fall, then you want to remove the receiving flask and replace it if there is still more chemical in the still pot. What this will indicate is that you had a mixture of chemicals. One of the chemicals has come over at the first temperature and that a second compound (of a higher B.P.) will be coming over at a higher temperature. There may even be a third compound if the solution you were distilling was an unknown. That is why it is so important to know the physical characteristics (M.P., B.P., etc.) of what you are trying to collect.

Simple distillation: the distillation of a single component or a mixture in which the boiling point difference is greater than ~40^°C.

Distillation of 10% salt water - a simple distillation.

If you want to be sure of the purity of a single liquid chemical or of any two components, then you can perform a simple distillation to remove any impurities ( as long as these impurities have a B.P. different from the solvent by 40 degrees or are non-volatile)

Setup the simple distillation apparatus using a 50 mL RBflask as the still pot. Put 20 mL of salt water in the 50 mL RB Flask with boiling stones. You will only need 2-3 stones. Start the distillation. Record the boiling range of the water. Stop the distillation when either: 5 mL of liquid remains in the still pot; or when the stillhead temperature quickly begins to rise after collection of the water; or when the stillhead temperature begins to fall after collection of the water. Never distill the still pot to dryness in this or any distillation. Chemicals remaining in the still pot may cause an explosion or fire.

Record the volume of the water recovered.

Record the refractive index of the water you've distilled and of the deionized water, and of tap water. (See page 18) Compare your distilled water's refractive index to the other two. Discuss your results in your notebook.

WASTE Spill and Disposal - A: All remaining liquids (stillpot, forerun, etc.) may be disposed of in the sink.

WASTE Spill and Disposal - E: Any acetone used to clean glassware. *THERE IS AN ACETONE WASTE JUG IN THE HOOD.

CHEMICALS:	LOCATION
10% NaCl	Hood #5
Acetone Bottles	Hood #4

SUPPLIES:
Organic kits
Blue glassware clamps	Org-Prep
Tubing	C-24 , C-25
Heat Guns	C-30 J , PL-5A
Heating Mantles	C-26
Vials, silicon grease, boiling chips, rubber bands	Org-Prep