Recrystallisation and Chemical Separations

Topics: Thin layer chromatography, Chromatography, Color Pages: 4 (857 words) Published: May 29, 2012

Recrystallization is used for the purification of solid compounds. The recrystallization process relies on the fact that majority of compounds are more soluble in hot solvent than in cold. The hot saturated solution containing the compound will have unwanted impurities and will be filtered out and cooled to produce the pure crystal constituents of the compound.

Thin layer chromatography can be used as a physical method to segregate compounds from natural sources. E.g. Spinach leaves are visibly green, but consist of a variety of components that have more colour than others. This experimental procedure uses compounds from spinach leaves that are exposed to chromatography, TLC plate to indicate the different pigments within the spinach extract.

‘Column chromatography in chemistry is a method used to purify individual chemical compounds from mixtures of compounds’ (Wikipedia, 2011). This method is similar to thin layer chromatography, but the compounds in the mixture are collected separately. Green dye is used in this experiment that consists of blue and yellow constituents.

Materials and Methods:

As per SCI105 Chemistry laboratory manual 2012, Brooks, 2012, page 12-19. With the following changes: The mass of recrystallization mixture is 10.05g not 10g.


Part A:

Compound (copper sulphate, sand and table salt) dissolved into hot water the solution turned a blue homogenous colour, leaving unwanted sand particles and a small amount of undissolved copper sulphate laying at the bottom of the beaker. Ethanol was added to the mixture and crystals started to from. After cooling duration crystals are visibly bound together.

Part B:

Spinach extract is visibly dark in colour with very little transparency, thick viscosity and no visible particles. The spinach extract on the TLC plate duration from origin to reach the solvent front was 10min. There were 6 different pigment movements on the TLC plate; constituent...
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