iodophthalein

noun

io·​do·​phtha·​lein ī-ˌōd-ə-ˈthal-ē-ən  ī-ˈäd-  -ˈthal-ˌēn 

-ˈthāl-

: a derivative of phenolphthalein or its soluble blue-violet crystalline disodium salt C₂₀H₈I₄Na₂O₄ used to render the gallbladder opaque to X-rays and formerly to treat typhoid carriers

called also tetraiodophenolphthalein