thymolphthalein
noun
thy·mol·phtha·lein
| \ -ˈthal-ˌēn, -ˈthā-ˌlēn, -ˈthal-ē-ən
\
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Medical Definition of thymolphthalein
: a crystalline compound C28H30O4 analogous to phenolphthalein and likewise used as an acid-base indicator