How can you find out which colours are in black biro ink biro ink does not dissolve in water?

To determine the colors in black biro ink, you can use chromatography, a method that separates the components of a mixture. By applying a small amount of the ink onto a piece of chromatography paper and then placing it in a solvent (like alcohol), the different dye components will travel at different rates, separating into distinct color bands. This technique reveals the various colors that make up the black ink.