What is the technique used to separate the components of ink?
A. Filtration
B. Distillation
C. Sublimation
D. Chromatography

Hint: Consider each of the separation techniques that are listed in the options and also consider the phases in which the components of the substance should be in order to be separated by that method.

Complete answer:
Let us look at each of the separation techniques and then determine whether the components of ink can be separated by those methods.
- Filtration
This separation technique is usually used when one of the substances in the liquid phase and the impurity or the other component is insoluble in that liquid and is present in the solid phase. We know that ink does not contain any components that are present in the solid phase, so this method cannot be used.
- Distillation
This method is used to separate any two liquids that are present in a mixture but have a vast difference in their boiling points. The components of ink do not have a major difference in their boiling points and thus this method cannot be used to separate ink.
- Sublimation
This method requires one of the substances in the mixture to be volatile, having a high vapour pressure and should undergo sublimation easily. Sublimation is when a solid is directly converted into the gaseous phase without going through the liquid phase. Ink has only liquid components that cannot undergo sublimation, so this technique cannot be used.
- Chromatography
This method is used with liquid substances that have and impart a certain colour to other substances. Inks, dyes, and food colouring agents are usually separated using chromatography. Spots are made with the ink on the paper and the paper is placed in a suitable solvent. The coloured components are ten separated over the paper after a while.

Hence, the correct answer to this question is ‘D. Chromatography’.

Note:
Although distillation is also used to separate liquids, there need to be a significant difference in the boiling points of the components and at least one of the components have to be colourless. Nevertheless, it is always more convenient to use chromatography to separate coloured mixtures.