phthalin / thalline [ˈθælɪn]
phthalin – n. – any colourless compound obtained by the reduction of a phthalein, which can be reconverted by oxidation especially C20H16O4 from phenolphthalein
thalline – adj. & n. – adj. – a plant part containing a thallus; n. a crystalline base, CH3OC9H9NH derived from quinoline and formerly used in the preparation of an antipyretic