Question

Dyes of an ink

• Give the principle involved in the separation of the mixture
• Give the technique of separation of the mixture.

Answer 1

By Chromatography

Principle – Chromatography is-a method by which the various components of a mixture e.g. dyes in an ink, are separated due to their difference in the rate of flow over an absorbent medium i.e. stationary phase e.g. filter paper under the influence of a solvent i.e. the mobile phase.
Chromatography – There are two phases and they are:
Stationary phase in chromatography, the adsorbent medium is known as the stationary phase e.g. filter paper made of cellulose.
Mobile phase the solvent or the solution that moves due to capillary action is known as the mobile phase.

The technique of Separation – Separation of dyes in ink by paper chromatography Ink prepared by dissolving different dyes e.g. A, B, C, D in a suitable solvent, is taken. A line is drawn with a pencil over a long strip of a filter paper.
Place the ink spot containing the different dyes on the filter paper as shown below.
The filter paper is then hung with its lower end dipped in a suitable solvent.
The solvent may be a mixture of ethyl alcohol and water poured into a tall jar, such that only a small lower part of the jar is filled.
The paper strip with the spot of ink at its is dipped into the solvent in a way that the spot itself remains above the liquid surface.
The solvent flows over the ink spot and the various components of the mixture, of dyes in the ink, are separated as shown below.