Separation of Metal Ions by Paper Chromatography

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Separation of Metal Ions by paper Chromatography Purpose: Chromatography (from Greek chroma, for colour, and praghein, to write) is a technique often used by chemists to separate components of a mixture. The first trial of chromatography was performed by Russian botanist, Mikhail Tsvet in 1906. He separated colour pigments from plant leaves by allowing a solution of these pigments to react with alumina (Al2O3), starch, and silica (SiO2) insoluble in water. Different colours of the bands have appeared during the reaction. That is how chromatography has taken its name. This discovery became very useful for many separation processes which caused the rapid development of chromatography techniques: paper chromatography, gas chromatography, high performance liquid chromatography. Continuous advances in this area of knowledge allowed to improve precision and quality of chromatography techniques. However the components of mixture are not always coloured so their position cannot be seen by eye. In such case, the colourless band can be detected with using UV light, or other compounds that react with the mixture. The purpose of the paper chromatography experiment was to identify the unknown solution by separating of metal ions and calculating their retention values (Rf). Retention factors are useful in comparing the results of one chromatogram to the results of another. This allows unknowns to be compared to known materials and detected. However the conditions in which the chromatography is performed must stay unchanged for both stationary and mobile phases. The formula to calculate the Rf constant is: Rf= distance traveled by spot (mm)distance traveled by solnent (mm) The metal ions used in this experiment were: manganese (II), iron (III), cobalt (II), nickel (II) and copper (II). They were dissolved in a solvent (9:1, acetone : 6M HCl) and reacted once again with

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