2. Recrystallisation

2. Recrystallisation - Recrystallisation Introduction The...

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Recrystallisation Introduction The aim of this experiment was to remove both soluble and insoluble impurities from a sample of p-toluene- sulphonamide using a process of two recyrstallisations, then to determine the melting points of the samples from both recrystallisations. Method First Recrystallisation The first recrystallisation involved removing two impurities from p-toluenesulfonamide, namely insoluble charcoal and soluble copper sulphate. To begin 2.5g±0.2g of the sample was put into a 250cm 3 round bottomed flask. A measuring boat was used to weigh the sample, which was then transferred to the flask. The exact mass used was 2.54g (2d.p.). To the flask was added 60cm 3 of distilled water. Then a reflux condenser was fitted to the round bottomed flask and an electric mantle used to boil the sample. 1 minute of boiling was sufficient enough to dissolve the solid and leave behind the insoluble charcoal impurity. Meanwhile a glass funnel (short and wide stemmed) was heated in a glass-drying oven. A 1000cm 3 beaker was used to create a hot water bath which was half full with boiling water. A dry conical flask was clamped into the bath with the hot, glass funnel in the neck of the flask. A suitably sized piece of filter paper was fluted and inserted into the funnel. Next the hot solution was filtered through the paper and funnel in small portions. The bulk of the solution was kept boiling in the mantle. The filtrate was then left to cool down to room temperature slowly before chilling it in an ice/water bath in another 1000cm 3 beaker. After 30 minutes the crystals which had formed were collected using a clean Buchner funnel and flask. A piece of filter paper was put in the funnel, ensuring it was the correct size to cover the holes and lie flat in the funnel. A little of the supernatant mother liquor was used to moisten the paper, and the suction was
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2. Recrystallisation - Recrystallisation Introduction The...

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