Sulphur, charcoal and potassium nitrate are the constituents of gunpowder. These can be separated as follows:
Step 1: Dissolve the gunpowder in water. Only potassium nitrate will dissolve.
Step2: Filter the solution. Filterate is the solution of potassium nitrate and residue contains sulphur and charcoal.
Step3: Evaporate the filterate to vapourize water. Potassium nitrate will be left behind and is thus separated.
Step4: Dissolve the residue in carbondisulphide which will dissolve sulphur but not charcoal. Filter the solution.
Step5: Charcoal is separated as the residue.
Step6: Evaporate the filterate to vapourize carbondisulphide. Crystals of sulphur are left behind.