a) To extract clove oil from cloves by steam distillation

Theory

• Steam distillation can be used to extract natural oils from plants – we will use steam distillation to extract clove oil from cloves

• Steam distillation is a separation process used to isolate compounds at temperatures below their decomposition temperatures - it is carried out by passing steam through the material and distilling off the immiscible liquids

Procedure

➢ Find the mass of the cloves using an electronic balance

➢ Set up the apparatus in the diagram

➢ The bunsen burner/hotplate is switched on and steam is passed through the flask for 40 minutes (or until ̴50cm3 of clove oil is collected)

Apparatus functions

1. Steam generator: a.k.a. copper kettle provides the steam. 

2. Safety tube: For safety - to remove excess water. 

3. Steam trap: To prevent excess steam entering the pear shaped flask. 

4. Liebig condenser: To condensate the emulsion

What are immiscible liquids?

Immiscible liquids are liquids that do not mix eg. Oil and water

What is the principle of steam distillation? *

The boiling point of two IMMISCIBLE LIQUIDS is below the boiling point of both liquids separately

Clove oil = 251°C

Water = 100°C

Together = 98°C

Why is steam distillation used to extract clove oil from cloves rather than direct distillation?

Clove oil has a high boiling point, if it were distilled directly, the oil would decompose at the high temperatures needed to bring the oils to the boil

What is the main constituent present in clove oil/what natural product in present in clove oil?

Draw the structural formula of this constituent

Eugenol

Give two safety precautions in this experiment

1) A safety tube is placed in the steam generator to prevent a build-up of pressure

2) Gloves should be worn when handling the cloves – Eugenol can burn the skin

Comment on the position of the safety tube in the steam generator

The safety tube must be below the level of the water to prevent steam escaping

What is the purpose of the steam trap in the apparatus?

What is the purpose of the steam trap in the apparatus?

A steam trap is used to collect any steam that has condensed and avoid it condensing into

and filling up the flask containing the cloves

What two substances were collected during the steam distillation?

Water and clove oil as an emulsion

What is an emulsion? *

An emulsion is a dispersion of small droplets of ONE LIQUID (OIL) IN ANOTHER LIQUID in

which it is not soluble (water)

Describe the appearance of the water- clove oil emulsion/distillate collected during the steam distillation

A milky coloured liquid

Why are whole cloves used rather than powdered cloves?

Whole cloves contain more oil than powdered cloves