In 1884 Remsen2 discovered sulfonefluorescein and called this class of compounds the sulfonephthaleins. Remsen and Hayes3 in 1887 attempted to isolate sulfonefluorescein, but obtained the ammonium salt of dihydroxybenzoyl-benzene-o-sulfonic acid, as shown in 1889 by Remsen and I, inn4 who prepared sulfonefluorescein by heating dihydroxybenzoyl- benzeneo-sulfonic acid at 185'. Their analyses of the amorphous material showed it to ...