Rheun or Rhein: How To spell?

The word Rheun is misspelled against Rhein, a noun meaning "Chrysophanic acid."

Word contains consecutive vowels 'EI' in between alphabets rh & n is misspelled as 'EU'
Wrong Spelling:  rh-eu-n 
Correct Spelling:  rh-ei-n 
Check more misspelled words of Rhein to spell it correct.