denature vs make impure

denature

verb
  • To take away a natural characteristic or inherent property of (a thing or a person). 

  • To combine fissile material with nonfissile material in order to prevent its use in an atomic weapon. 

  • To alter its original form or state, especially of a protein, by heat, acidity etc. 

  • To add something to (alcohol) that makes it unsuitable for consumption but leaves it suitable for most other purposes. 

make impure

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