black tar vs substance

black tar

noun
  • An illicit drug formed from the incomplete acetylation of morphine, containing a variable percentage of heroin. 

substance

noun
  • Drugs (illegal narcotics) 

  • Physical matter; material. 

  • Material possessions; estate; property; resources. 

  • Hypostasis. 

  • Substantiality; solidity; firmness. 

  • The essential part of anything; the most vital part. 

  • A form of matter that has constant chemical composition and characteristic properties. 

verb
  • To give substance to; to make real or substantial. 

How often have the words black tar and substance occurred in a corpus of books? (source: Google Ngram Viewer )