Nitrosyldisulfonate (ON($03)2) has been prepared by the oxidation of hydroxylaminedisulfonate (HON(SO3)2) with oxidizing agents such as lead dioxide, potassium permanganate or silver oxide. We have found that nitrosyldisulfonate can be formed by the electrochemical oxidation of hydroxylaminedisulfonate on a platinum electrode. This paper deals with the measurement of the oxidation-reduction potential of the nitrosyldisulfonate/hydroxylaminedisulfonate redox system and the determination of the third dissociation constant of hydroxylaminedisulfonic acid.
Potassium hydroxylaminedisulfonate (I) (Nisshin Kako Co.) was purified by recrystallization from slightly ammoniacal solution. Potassium nitrosyldisulfonate (II) was prepared by Haga's method using silver oxide, partly modified in respect to proportions of reagents. The solid product was recrystallized from water made slightly alkaline with potassium hydroxide.
Salts(I) and (II) prepared as described above were dried in a vacuum desiccator over phosphorous pentoxide. They were analysed for sulfur and oxidizing power after hydrolysis by boiling with hydrochloric acid.
A potentiometric titration was carried out by measuring the e.m.f, of the cell :