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Studies on thermodynamic properties of copper in molten NaOH

โœ Scribed by Hidetaka Hayashi; Shiro Yoshizawa; Yasuhiko Ito

Publisher
Elsevier Science
Year
1983
Tongue
English
Weight
544 KB
Volume
28
Category
Article
ISSN
0013-4686

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โœฆ Synopsis

Thermodynamic behaviour of copper in molten NaOH at 623K (35O"C) has been studied. The solubility product of cupric oxide, Ksp_-2. was determined to he 2.5 x lo-" by chemical analysis. The standard potential of the Cu/Cu+ couple was found to be 1.97 V vs Na/Na+ and that of the Cu+/Cu*+ couple was 1.87 V vs Napa', respectively. Moreover, the standard potential of the Cu/Cu,O and Cu,O/CuO couples were determined by the use of stabitizd zirconia and compared with the values derived from published thermochemical data. Finally IL,,-I, the solubifity product of cuprous oxide, was evaluated tobe3.0x10-15.

From the experiment, the following conclusions were obtained.

(1) In this system,coppercanbcoxidiied to itsdivalent state, suchascupric oxideorcupricion, through its univalent state, such as cuprous ion or cuprous oxide, in the presence of oxygen.

(2) Solubility products of the oxides of copper are much larger than that of nickel oxide, which behaves as a protective film. Thus, copper is not suitable for materials to be used in this media.

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