This method is often used in the food industry. It is used to identify chemicals (coloring agents) in foods or inks. For example, if a scientist wants to know how many substances are in a particular blob of ink, paper chromatography can be used.

Below is an illustration of using chromatography to separate and identify the different chemicals in a particular ink (mixture).

A blob of ink is smeared on a special paper called filter paper. The piece of paper is placed in a trough of solvent. The solvent used depends on the chemicals in the ink blob. As the paper gets soaked upwards, it attracts the various chemicals in the ink blob. Because different chemicals

have different rates of attractions to the solvent, the different chemicals will travel upwards in different amounts. Sometimes, a chemical may not react at all. If a different solvent is used, all the various chemicals may travel at a completely different rate.