DISTILLATION AT ATMOSPHERIC TEMPERATURE

Simple distillation at atmospheric pressure may be used to purify liquid that boils below about 2000C without decomposition.
To begin with, clamp the flask and fit it with the distillation head.
If the boiling temperature isn’t known, use water cooled condenser – A Liebig condenser.

It helps to secure the joints with a clip.
Cradle the condenser on the fixed jaw of the clamp
Close the upper jaw to hold it firmly but not too tightly. It should still be possible to rotate the condenser.
Attach a tip take off band and secure it with a clip.
Three receiving flasks are usually needed for distillation.
The largest should be big enough to contain at least three quarters of the liquid to be distilled.

In a quantitative distillation, all three flasks with their stoppers must be labeled and weighed before collecting any distillate in them.
Attach the 1st receiving flask supporting it with a cork ring on a lab jack.

The cork ring should be oversized so that it will cradle the flask should it fall from the take off end.
Alternatively, clamp the flask (not the take off end) using a further clamp on a stand.
The early distillate may be very volatile and flammable, so attach a length of tubing to lead any uncondensed vapor down the zinc with running water or into an extractor port.
Attach the rubber tubing from a lower side arm of the condenser to the water tap.
Slide it up until is firmly fixed.
Water should always flow up the condenser jacket.
Keep it steady but not too powerful water flowing and check it from time to time.

It is best to wire the tubing unto the condenser.
If the liquid is known to have a high boiling temperature, an air condenser can be used from the start.
When carrying out distillation at atmospheric pressure, a few anti-bumping granules should be added to ensure smooth boiling.
Use them only once and just a few at a time.
They should be added to the flask before the liquid. Don’t try to add them through an already wetted funnel they may stick to the sides.
The stem of the funnel used to introduce the liquid into the flask, must extend below the side arm or crude liquid may accidently get into the condenser.

The flask should be filled not more than two third full from the start of the distillation.
With care, fix a quick fit thermometer into the distillation head to monitor the distillation temperature.
Remember they are expensive and fragile.
The usual source of heating is a water or oil bath set on a hot plate or stirrer hotplate.

The foil prevents any spillage burning on the hotplate.
It’s wise to have the bath on a lab jack so that the heat source can be raised or lowered quickly.
The level of the oil in the bath should be positioned just about the level of the liquid in the flask.
Switch on the stirrer hotplate, adjust the stirring rate.
And at first set the heating rate to maximum until the liquid starts to boil.
Suspend a thermometer in the oil to monitor the temperature of the heating bath.
At the first sign of boiling, reduce the heat to certain point that a steady boiling is just maintained.

The temperature usually begin to rise rapidly but soon settles down to a steady value as vapor begins to condensed about the thermometer bulb and drifts from the outflow of the distillation end.
Record this initial temperature, and adjust the bath temperature to between 30 – and 500C above it.
Distillate should drip into the receiver at about 1 drop a second. The first few drops may be cloudy,
When the temperature has remain steady for half a minute, note it , then change the receiver and collect the bulk of the liquid in the second flask.

If the rate of distillation becomes too high, the heating can be quickly reduced by lowering the oil bath.
Generally the bath should be lowered as the liquid levels inside the flask falls during distillation so avoiding the  danger of the flask overheating and causing returning condensate to decompose,
When most of the liquid is distilled, the temperature may begin to fall slightly, until the vapor of higher boiling reaches the thermometer, at this point, note the temperature and change the receiver again.
After this had been collected, a little more liquid may distill over giving 3 fractions in all.

At the end of the distillation lower the lab jack to remove the heat source, don’t heat the flask to dryness or even nearly so, it could be dangerous, for example the residue may be explosive or decompose to give toxic fumes.
Finally, let the apparatus get cold before dismantled it, and clean it as soon as possible.