demountable vs replaceable

demountable

adj
  • Able to be removed from its mount; designed to be dismantled. 

noun
  • A temporary and portable building, especially a portable classroom in a school. 

replaceable

adj
  • Capable of being replaced. 

noun
  • Anything that can be replaced. 

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