Often a pure substance needs to be isolated from a mixture, for example from a natural source (where a sample often contains numerous chemical substances) or after a chemical reaction (which often give mixtures of chemical substances).
Seringkali zat murni perlu diisolasi dari campuran, misalnya dari sumber alami (di mana sampel sering mengandung banyak zat kimia) atau setelah reaksi kimia (yang sering memberikan campuran zat kimia).