Illegal dope is often identified by its fraudulent adulteration. Chalk, bicar-bonate of soda, sand, and even ashes, are used to dilute it.
Contents of bottles, glass, etc, found at the scene of an unexplained death, should always be preserved ad analyzed for possible poisons.
In arson cases, oil often can be detected an ashes. Place ashes in screw top container and heat to 80º F. When opened oil fumes can be detected by smell.