Tsvet's Column: The First Chromatogram

In 1903 a Russian-Italian botanist working in Warsaw poured an extract of green leaves into a glass tube packed with powdered chalk, washed it through with petroleum solvent, and watched the single green smear pull apart into separate coloured bands down the column. Mikhail Tsvet called the result a *chromatogram* — a writing in colour — and it is the ancestor of every separation in this batch. His insight was that leaf green is not one substance: it is two chlorophylls and a family of yellow and orange carotenoids, and they stick to chalk with different strengths. The one that clings least travels furthest. The technique was ignored for thirty years, partly because Tsvet published in Russian and partly because the leading plant chemist of the day insisted the bands were artefacts. You can settle that argument yourself in an afternoon with chalk and a glass tube.