Distillation is the process of separating two liquids on the basis of the differences in their boiling points. The process starts with the heating of the liquid mixture to boiling point and the more volatile liquid will evaporate at lower temperature than the less volatile liquid. The vapors are then condensed and collected and are termed as distillate, which is a purified form of the original liquid. Alcohol and water are very easy to separate as they have a large difference in their boiling points, ethyl alcohol boils at 78.5°C whereas water boils at 100°C.
Basic distillation procedure:
- If a thermometer is being used for the temperature check in the distillation procedure, it must first be calibrated by placing it on ice and allowing it to reach thermal equilibrium and then place it in boiling water and again allow it to reach thermal equilibrium. The temperature on the thermometer should not deviate more than two degrees than the expected values or it must not be used if so.
- Now the distillation or the round bottom flask is filled with the liquid that is to be distilled. It should not be more than one-third of the total volume if the distillation flask to ensure the purity of the vapors being formed. The liquid to be distilled could be any two liquids mixed or a wine or alcohol sample that is subjected to purification, as distillation gives us a purified form of the original liquid.
- Now the vapor will begin to form as the temperature is applied to the distillation flask. As the vapor will pass through the condenser they will start to condense and drip into the collection flask that is placed on the other end of the condenser.
- An appropriate rate of distillation is about 20 drops per minute. The rate of distillation should be appropriate, neither too fast and nor too slow, just slow enough to allow all drops of the distillate to condense to liquid in the condenser.
- Condensation is an important step in the distillation process as the ethanol is highly inflammable i.e., it catches fire easily when comes in contact with high temperatures, hence, constant cooling of the chamber is an important step.
- If there are more than two liquids that are to be separated on the basis of the difference in their boiling points then the process is called fractional distillation. Where when the liquid with least boiling point is collected, the temperature is then increased to the boiling point of the other liquid and a new flask is placed to collect vapors of the different liquid.
- As the temperature still begins to rise, place a new flask to collect the distillate that now is formed.
- Remove the distillation flask from heat before all the liquid is evaporated as it increases the chances to catch fire or explode due to danger of presence of some peroxides. We should never distillate to dryness as in the empty distillation flask the temperature will rise very rapidly causing the vapors to catch fire easily.
- We should make sure that all joints of the distillation point are secured tightly as any dissipation of vapors will cause their ignition.
- Proper condensation system or the cooling system is very important to prevent the explosion of the distillation plant.
Simple distillation is effective and useful when separating two liquids with different boiling points. This difference in their boiling points should be more that at least twenty degrees, or the efficiency of the distillation will not be as desired.
The two processes of simple distillation and fractional distillation are almost similar and the apparatus of both the processes are also similar just that in case of the fractional distillation apparatus a ratiocination column is attached to the top of the distillation flask and beneath the condenser., which provides the surface area where the rising vapors condense and subsequently re-vaporize.