Coexistence of Liquid Phases in the Sodium Polyphosphate–Chromium Nitrate–Water System

Author： de Azevedo M.M.M. Bueno M-I.M.S. Davanzo C.U. Galembeck F.

ISSN： 0021-9797

Source： Journal of Colloid and Interface Science, Vol.248, Iss.1, 2002-04, pp. : 185-193

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

The formation of coexisting liquid phases out of aqueous aluminum polyphosphate solutions was previously suggested as an essential step in aluminum polyphosphate nanoparticle formation. This hypothesis could not be directly verified because the separation of the two phases is very difficult, but a different situation was found in the case of chromium (III) polyphosphate. The phase diagram of the sodium polyphosphate–chromium nitrate–water system at 25°C presents an extensive region with two coexisting liquid phases (L–L), together with a single liquid phase (L) and a solid–liquid (S–L) domain. Within the L–L region, admixture of the reagents produces initially a turbid liquid, out of which two transparent liquid phases separate in a short time, under gravity: one is dense, dark, and viscous while the other has a light color and a lower density. The amounts of the separated phases were determined, as well as their viscosities, densities, pH, UV-vis spectra, and relevant molalities: P (from polyphosphate), Cr³⁺, NO^-₃₊, and Na⁺. The two liquid phases undergo significant color, pH, and viscosity changes with time. The calculated phase diagrams display the major features of the experimental phase diagram. © 2002 Elsevier Science (USA).