KAGAKU KOGAKU RONBUNSHU
Online ISSN : 1349-9203
Print ISSN : 0386-216X
ISSN-L : 0386-216X
Special Issue [Progress of Practical Crystallization Technology]
Eutectic Formation from Melt Mixtures of Hydrates of Nickel and Cobalt Salts
Yasuyuki Watanabe Izumi Hirasawa
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2018 Volume 44 Issue 1 Pages 3-11

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Abstract

Based on the idea that eutectic formation is an useful technology for controlling the melting points of latent heat storage materials over a wide temperature range, precise experimental studies were carried out on the inevitability of eutectic composition of salt hydrate mixtures. Phase diagrams were developed from heating curves of two pseudo-binary systems, Ni(NO3)2·6H2O–CoCl2·6H2O and NiCl2·6H2O–Co(NO3)2·6H2O. The melting points of individual hydrates were 53.5, 53.0, 51.5 and 53.5°C, respectively. In the two binary systems, similar simple eutectic formations were recognized under the same conditions of 30°C and equimolar composition. The crystal compositions in the systems changed depending on the binary mixing ratio. At the same time, new crystal phases that were not attributed to either of original salt hexahydrates were also generated, and the contents of the new phases became maximum at the eutectic points. The two eutectics generated were found to have the same crystal composition as each other as analyzed by X-ray powder diffraction patterns. Consequently, it was concluded that the eutectics were formed through the mutually equivalent exchange of dissociated ions. Further, the inevitability of those compositions was determined as the mixing ratio at which the mutually equivalent exchange might be maintained for all dissociated ions.

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© 2018 The Society of Chemical Engineers, Japan
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