Question

You have a sample consisting of unknown concentrations of methanol, ethanol, and 1-propanol. That is, you have one jar that contains all three of these chemicals. You don’t know the concentrations of the chemicals. You also have individual 100% solutions of methanol, ethanol, and 1-propanol. So, one jar of 100% methanol, one jar of 100% ethanol, one jar of 100% 1- propanol. You have methylene chloride to use as a solvent. determining the concentration of each alcohol in your unknown mixture

Answer 1

Since all the three alcohols are at the bottom of the analogous series of R-OH group, it is very difficult to separate them by simple distillation.

Hence,

1. the unknown mixture must be measured and its volume must be noted.

2. mix a known amount of methylene chloride to the mixture. This will form MeOH-CH2Cl2 and EtOH-CH2Cl2 lower boiling azeotropes that boils at approximately 40oC.

3. However, propanol doesn't form such azeotrope and will boil at its boiling point (i.e. 86 oC). Hence, propanol-1 will be separated and its volume can be noted.

4. The remaining azeotropic mixtures can be separated by a process called Azeotropic distillation. (Refer: http://www.freepatentsonline.com/5152876.html) The distillation (azeotropic) can be stopped when the amount of methylene chloride added initially is completely recovered.

This procedure may lead to 90-95% separation of all the components from each other.