Quasin or Quassin: How To spell?
The word Quasin is misspelled against Quassin, a noun meaning "The bitter principle of quassia, extracted as a white crystalline substance; -- formerly called quassite."
Quassin has double "ss" is mispronounced as "s"Remember double 'SS' in between the strings qua & in which should not be misspelled with single 'S'
Wrong Spelling:  qua-s-in  Correct Spelling:  qua-ss-in 
Check more misspelled words of Quassin to spell it correct.