Measurements of the isobutyric acid (IBA) concentration in a dilute si
lica gel, vs that in an IBA and water reservoir in equilibrium with th
e gel, show that first-order phase transitions occur at 15 and 19 degr
ees C, but not at 23 degrees C. The data show that the coexistence cur
ve of this gel/mixture system is narrow, contained within that of the
pure mixture, and lies below a broad region of apparent metastability.
The existence of a metastable state above the critical temperature of
the gel/mixture system is strikingly similar to the behavior observed
for random-field magnets.