New arylhydrazones of indane-1,3-dione  –  3-(2-hydroxy-3-sulfo-5-chlorophenylhydrazone)indane-1,3-dione (1), 3-(2-hydroxy-3,5-disulfophenylhydrazone)indane-1,3-dione (2), 3-(2-hydroxy-3-sulfo-5-nitro­phenylhydrazone)indane-1,3-dione (3), 3-(2-hydroxy-4-nitrophenylhydrazone)indane-1,3-dione (4) and 3-(2-hydroxyphenylhydrazone)indane-1,3-dione (5) have been synthesized  and characterized by IR, ¹H and ¹³C NMR spectroscopies, ESI-MS and elemental analysis. The collected information confirms that 1−5 exists in DMSO solution in hydrazone form, being stabilized by an intramolecular hydrogen bonding. The dissociation constants were determined by potentiometric titration method and the obtained values of the pK₁ and pK₂ were in the range from 5.31 and 8.42 to 5.94 and 9.29, respectively, and they were in a good agreement with the expected ones for this kind of compounds