liquefaction vs smelting

liquefaction

noun
  • Process of being, or state of having been, made liquid (from either a solid or a gas) 

  • The liquid or semiliquid that results from this process. 

smelting

noun
  • The process of melting or fusion, especially to extract a metal from its ore. 

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