薬品のポーラログラフ的研究 (第19報)

チオセミカルバジドと重金属との反応

抄録

Thiosemicarbazide (T) shows anodic wave due to the reaction with mercury when using a dropping mercury electrode. At pH below 5, E_1/2+0.01V, diffusion current constant K_D=2.05 (μA⋅mM^-1 mg^-2/3⋅sec^1/2), and n=1, and above pH 5, E_1/2=+0.36-0.07 pH, K_D=8.23, and n=4. These facts were confirmed through microcoulometry, controlled potential electrolysis, and amperometric titration with mercury or silver nitrate. This polarographic method is used for determination of thiosemicarbazide and does not interfere in the determination of thiosemicarbazones. With rotating platinum electrode, thiosemicarbazide shows further oxidation wave at the positive potential. In acid solution, thiosemicarbazide reacts with equimolar amount of mercury nitrate but immediately undergoes decomposition to mercury and a mercuric complex [T₂Hg]²⁺ [NO₃^-]₂. This complex was isolated and from its infrared spectra, it was found that thiosemicarbazide is coordinated to mercury not by N and N but by N and S. In alkalinity, thiosemicarbazide reacts with 4 moles of mercury nitrate to form mercury sulfide, mercury-amino complex, and nitrogen.