experiment: melting point and recrystallisation
step 2: Dissolve the Impure Sample in Hot Solvent
a) Use about 1 g of acetanilide (weighed accurately). Add 20 mL of hot distilled water to the impure sample with 2 or 3 anti-bumping granules in a conical flask.
b) Heat this mixture until it is gently boiling. If all the sample has not dissolved, add further 5 mL portions of hot distilled water until the sample has either completely dissolved, or no more material will dissolve, in the hot solvent. Record the volume of water used. If you need more than 45 mL of water, consult a demonstrator
c) Remove the sample from the source of heat and allow it to stand for 2 minutes. If in this time the sample starts to crystallise, then the solution is too concentrated to filter and more solvent should be added, otherwise the sample may crystallise in the filter paper during the hot filtration step.
- 1) What would happen if you added too much solvent at the dissolving step (Step2)?
- 2) Is your sample pure? Explain how you came to your conclusion. Hint: you need to consider TWO indicators of purity?