Question

I performed a simple distillation on a unknown liquid and i ended up with two layers, is that normal?

Answer 1

Distillation is a process of separating two or more liquids by exploiting the different boiling temperatures of liquids. The two main kinds of distillation are simple distillation and fractional distillation.

In simple distillation, when the liquid is heated in a flask, the more volatile liquid (the liquid with the lower boiling point) will typically evaporate first and the vapor will pass into a condensing column, where it condensed into a liquid But if heating further will cause the less volatile liquids to evaporate and distill at higher temperatures.

Since, in your case simple distillation of an unknown liquid afforded two layer it implicates that the your unknown liquid is most probably a crude mixture of two liquid along with other nonvolatile impurities where one liquid is lighter and other liquid is heavier. Since the mixture is impure so you are unable to differentitate the two layers but after simple distillation, being free from other nonvolatile colour impurities, two liquids are forming two distinct layer.

Or chances are there, at elevated temperature, some reaction (example decomposition) can occur which results in the formation of two liquids with different densities.

The best way is to go for fractional distillation (where a fractionating column is placed between the boiling flask and the condenser) for an unknown liquid so that if your unknown liquid consists of two or more liquids with different boiling point, they can be collected separately.

Here, you can analyze (GC etc) your unknown liqiuid as well as two layer of liquids obtained after simple distillation to match their identity.