GCSE-readyCore practical: investigating inks
Core practical 2.11 uses simple distillation and paper chromatography to find out what is in an ink.
Simple distillation of ink
2. The thermometer bulb sits level with the side arm, to measure the temperature of the vapour leaving.
3. The vapour passes into a condenser. Cold water flows in at the bottom and out at the top, so the condenser stays full and cold.
4. The liquid that collects (the distillate) is the solvent. If the thermometer reads 100 °C, the solvent is water. The dyes stay in the flask.
Cool the collecting tube in ice to stop the vapour escaping. Fractional distillation is needed for liquids with boiling points close together.
Chromatography of the dyes
2. Put small spots of each ink (and known dyes) on the line.
3. Stand the paper in a beaker of solvent with the solvent level below the line, and cover the beaker.
4. Remove the paper before the solvent reaches the top and mark the solvent front.
5. Measure from the pencil line to the centre of each spot and to the solvent front.
Interpreting results
The number of spots shows how many dyes are in the ink. Spots at the same height (same Rf in the same solvent) as a known dye are probably that dye.
Choosing a method: filtration (insoluble solid from liquid), crystallisation (soluble solid from solution), simple distillation (solvent from solution), fractional distillation (mixed liquids), chromatography (dyes).
A dye spot moves 3.6 cm while the solvent moves 8.0 cm. Calculate the Rf value.
- Rf = 3.6 ÷ 8.0
- = 0.45
Answer: 0.45
Distil ink to collect the solvent (100 °C means water); use chromatography to separate the dyes. Use a pencil start line above the solvent, cover the beaker and mark the solvent front. Rf = spot distance ÷ solvent distance.
- Simple distillation
- Separating a solvent from a solution by boiling it and condensing the vapour.
- Chromatography
- A method that separates the substances in a mixture as a solvent (mobile phase) carries them different distances through paper (stationary phase).
- Solvent
- The liquid in which a solute dissolves.
- Fractional distillation
- Separating a mixture of liquids with different boiling points, using a fractionating column. Used for crude oil.
- Filtration
- Separating an insoluble solid from a liquid using filter paper.
- Crystallisation
- Getting crystals of a soluble solid by evaporating some solvent from its solution and leaving it to cool.
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In distillation, what is the condenser for?
- To heat the mixture
- To cool the vapour so it turns back into a liquid
- To filter out the dye
- To measure the boiling point
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Answer: To cool the vapour so it turns back into a liquid
Cold water in the condenser cools the vapour.
During distillation of a solution the thermometer reads 78 °C. Which solvent is most likely being collected?
- The dye
- Ethanol
- Water
- Salt
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Answer: Ethanol
Ethanol boils at about 78 °C.
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- Pearson Edexcel GCSE Chemistry (1CH0) specification, topic 2.7, 2.8, 2.10, 2.11
- Pearson Edexcel GCSE (9-1) Chemistry (1CH0) specification
Checked by the GCSE-ready editorial team, 17 October 2026. Last updated 2 October 2026. Spotted a mistake? Tell us and we will fix it.
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