Question

Gun powder is a mixture of sulphur, charcoal and potassium nitrate (KNO3).
How would you separate it into its constituents?

Answer 1

First dissolve gunpowder in water. Only KNO3 will dissolve.
Then filter the solution. The residue left behind will be sulphur and charcoal. The filtrate obtained is KNO3 solution.
Heat the KNO3 solution until water evaporates. Pure KNO3 is left behind.

Now dissolve the sulphur and charcoal in Carbon Disulphide solution. Only sulphur will get dissolved. Filter this solution, and the residue obtained will be of charcoal. 
Now heat the filtrate (Carbon Disulphide + Sulphur solution). Carbon disulphide will vaporize away and Sulphur will be left behind.

Now you have KNO3, charcoal and sulphur.