Water can be purified with the help of activated carbon. Impurities, e.g. organic substances, adsorb on activated carbon and are thus filtered out of the water. A filter loses its filtering properties when it can no longer adsorb a substance. Then a so-called breakthrough occurs and the filter no longer has any filtering properties for this impurity.
In this experiment the breakthrough curve of the dye indigocarmine on activated carbon is determined. For this purpose, the dye is placed on activated carbon and the colour of the filtrate is measured until it returns to the initial value of the unfiltered solution.