Chromatography is a technique for separating and analysing a mixture of gases, liquids or disolved substances. This is achieved by using two immiscible substances, one of which (the mobile phase) transports the sample mixture through the other (the stationary phase). The apparatus for paper chromatography is shown. A piece of filter paper is the stationary phase and a chosen solvent the mobile phase. Tiny spots of the sample are applied to the paper, which is then developed. The different coloured components of the mixture separate as the solvent rises.
© Science Museum / Science & Society Picture Library