N,N'-bis(β-1-piperazylethyl) dithiooxamide forms soluble, colored chelates with a number of the transition metal ions. This reagent might have several advantages over other substituted dithiooxamides, since both it and the chelates are water soluble. In solution the reagent acts as a dihydroxy base, deriving its basicity from the presence of the substituent piperazine rings. Potentiometric titration with hydrochloric acid yielded K1= 1.70 x 10-5 and K2 = 1.14 x 10-5 for the two basic dissociation constants. In the presence of copper (II) ion this reagent forms two chelate species which were determined absorptimetrically to have the compositions Cu2R and CuR. The latter complex, containing the metal ion and the ligand in equimolar quantities, is suitable for use in the spectrophotometric determination of copper at concentrations as low as 0.05 mg per liter. Formed under conditions of an excess of reagent in ammoniacal solution, this complex exhibits a molar absorptivity of about 18,000 at its wave length of maximum absorption. Although the reagent is not specific for copper, the simplicity of the method and its high sensitivity recommend its use in the determination of copper.
Proceedings of the Iowa Academy of Science
©1961 Iowa Academy of Science, Inc.
Baker, H. Weldon and Pflaum, Ronald T.
"A New Sensitive Reagent for the Spectrophotometric Determination of Copper,"
Proceedings of the Iowa Academy of Science, 68(1), 174-181.
Available at: https://scholarworks.uni.edu/pias/vol68/iss1/29