Core practical - investigating the composition of inks

Question 1

Aim of this practical:

Answer 1

To investigate the composition of inks using simple distillation and chromatography.

Question 2

Simple distillation: Method: (4)

Answer 2

1- Add a small volume of ink to a flask. Connect the flask to the fractionating column and secure it with a stand, boss and clamp.
2- Attach a condenser to the top of the fractionating column, connect it to a cold water tap and sink, and secure it over a beaker.
3- Heat the flask using a Bunsen burner, reducing the flame as necessary to achieve gentle simmering.
4-Collect a small sample of the distilled solvent, then turn the Bunsen burner off.

Question 3

Paper chromatography: Method: (5)

Answer 3

1- draw a pencil line across the chromatography paper, 1-2 cm from the bottom
2- use a pipette or capillary tube to add small spots of each ink to the line on the paper
3- place the paper into a container with a suitable solvent in the bottom
4- allow the solvent to move through the paper, but remove the chromatogram before it reaches the top
5- allow the chromatogram to dry, then measure the distance travelled by each spot and by the solvent

Question 4

Explain why the distances travelled by each spot were measured in mm, rather than in cm. (2)

Answer 4

• measurements in millimetres are more precise than those in centimetres.
• they will give more precise Rf values.

Question 5

identify the 3 hazards in this practical:

Answer 5

• Hot apparatus
• Bunsen burner flame
• Harmful solvent

Question 6

Hot apparatus: harm and precautions

Answer 6

h= Skin burns
p= Allow apparatus to cool before touching it

Question 7

Bunsen burner flame: harms and precautions (4)

Answer 7

h= Skin burns, fire
p= Keep hair and clothes tucked in, Do not bring flammable solvents near to the flame

Question 8

Harmful solvent: harms and precautions: (4)

Answer 8

h= Skin irritation, Breathing difficulties
p= Avoid skin contact, Ensure adequate ventilation or use a fume cupboard