phentetiothalein

noun

phen·​tet·​io·​tha·​lein ˌfen-ˌtet-ī-ō-ˈthal-ē-ən, -ˈthāl- 

: a substance or its disodium salt C₂₀H₈I₄Na₂O₄ isomeric with iodophthalein used especially formerly as a radiopaque medium in cholecystography and in tests of liver function

called also phenoltetraiodophthalein