D. Tuma et Gm. Schneider, Determination of the solubilities of dyestuffs in near- and supercritical fluids by a static method up to 180 MPa, FLU PH EQUI, 160, 1999, pp. 743-757
Solubilities of the synthetic dyestuff 1,4-bis-(octylamino)-9,10-anthraquin
one in CO2, N2O, CClF3, and SF6 and additionally of the natural dyestuff al
l-trans beta-carotene in CO2 and N2O were measured by a static analytical s
et-up consisting of a high-pressure autoclave coupled to a UV/VIS-spectroph
otometer. In the case of 1,4-bis-(octylamino)-9,10-anthraquinone isotherms
were recorded for temperatures from 282 to 341 K and over a pressure range
from 6 to 110 MPa, whereas for all-trans beta-carotene experiments both on
solubility and solubility kinetics were carried out in the temperature and
pressure ranges from 308 to 350 K and 8 to 180 MPa, respectively. For both
substances it could be found that solubility normally increases with rising
temperature at a constant solvent density and equally with rising solvent
densities at a given temperature. N2O proved to be the best solvent, follow
ed by CO2. At solvent densities corresponding to normal liquids, however, t
he curvature of the solubility isotherms (plot concentration versus density
) changed its sign and as a consequence solubility maxima were observed for
the systems 1,4-bis-(octylamino)-9, 10-anthraquinone + SF6 and beta-carote
ne + CO2. Additionally, beta-carotene showed a temperature dependent all-tr
ans to cis isomerization at supercritical conditions and even thermal decom
position with further increasing temperatures. (C) 1999 Elsevier Science B.
V. All rights reserved.