Phthalen or Phthalein: How To spell?

The word Phthalen is misspelled against Phthalein, a noun meaning "One of a series of artificial organic dyes made as condensation products of the phenols with phthalic acid, and well represented by phenol phthalein. Their alkaline solutions are fluorescent."

Word contains consecutive vowels 'EI' in between alphabets phthal & n is misspelled as 'E' as letter 'I' is phonetically ignore
Wrong Spelling:  phthal-e-n 
Correct Spelling:  phthal-ei-n 
Explore spell check of Phthalein to spell without errors.