chamber pot vs chemical toilet

chamber pot

noun
  • A container used for urination and defecation, particularly those used in early modern towns before the advent of the flush toilet. 

chemical toilet

noun
  • A toilet or chamber pot which treats waste in place with chemical disinfectants and deodorizers, as in airplane lavatories. 

How often have the words chamber pot and chemical toilet occurred in a corpus of books? (source: Google Ngram Viewer )