cocaine vs crack cocaine

cocaine

noun
  • Any derivative of cocaine. 

  • An addictive drug derived from coca (Erythroxylum) or prepared synthetically, used sometimes medicinally as a local anesthetic and, often illegally, as a stimulant. 

crack cocaine

noun
  • A mixture of baking soda and cocaine in solid form that is smoked in a pipe as a narcotic. 

  • A mixture of salt substitute, ether, and cocaine in a semi-liquid form, which is far more potent than if made with baking soda alone. 

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