Fractionation

Noun

1. A separation process in which a certain quantity of a mixture is divided up into smaller quantities (fractions) in which the composition changes according to a gradient; an instance of this process.

   "Methane is separated from other hydrocarbons in a gas fractionation plant."

2. The division of a total dose of radiation into fractions.
3. A preliminary stage of encryption that divides each plaintext symbol into several ciphertext symbols.
4. A form of hypnosis where the patient is made to enter and leave a trance state many times in quick succession.