ferric vs indurate

ferric

adj
  • Pertaining to, derived from, or containing iron. 

  • Of compounds of iron in which it has a valence or oxidation number of 3 

indurate

adj
  • Hardened, obstinate, unfeeling, callous. 

verb
  • To inure; to strengthen; to make hardy or robust. 

  • To harden or to grow hard. 

  • To make callous or unfeeling. 

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