disperse vs thicken

disperse

verb
  • To disseminate. 

  • To break up and disappear; to dissipate. 

  • To scatter in different directions. 

  • To separate rays of light, etc., according to wavelength; to refract. 

  • To distribute throughout. 

adj
  • Scattered or spread out. 

thicken

verb
  • To strengthen; to confirm. 

  • To become thicker (in the sense of wider). 

  • To become thicker (in the sense of more viscous). 

  • To make thicker (in the sense of more viscous). 

  • To make thicker (in the sense of wider). 

  • To make more frequent. 

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