Moving blue band caused by cooperation of diffusion and phase separation.
Diffusions of Cu(2+) and Fe(3+) in gelatin generate a moving blue band. It is formed by a diffusion of Cu(2+) and a phase separation of gelatin with diffusing Fe(3+). The diffusing Fe(3+) forms Fe(OH)(3) colloids and gathers gelatin molecules from the surroundings. The diffusion of gelatin molecules generates the concentration gradient, resulting in a gel/sol transition in the dilute phase. In the region where the concentration of Fe(3+) is high enough, the gel remains hard, while a sol phase appears under the hard gel. The absorption spectrum of Cu(2+) depends on the concentration ratio of Cu(2+) to gelatin. As a consequence, we can see a blue band in the restricted region between the diffusing front of Cu(2+) and the phase separation front. The movement of the blue band is caused by a coupling of a simple diffusion and the phase separation.
Sato
Chiori
C
Department of Chemistry and Chemical Engineering, Yamagata University, Jonan 4-3-16, Yonezawa 992-8510, Japan. ashioi@mail.doshisha.ac.jp
Esumi
Naoki
N
Ban
Takahiko
T
Shioi
Akihisa
A