was added to separate portions (1.5 mL) of
the previous solution and transferred into glass vials (10 mm
in radius) covered with parafilm having fine pores and
stored at room temperature. Monolithic clear gels were
formed within 7 days. The monolithic materials of the
entrapped indicators were left for another 7 days to obtain
solid transparent crack-free disks with 0.80–0.82 mm
thickness, 7 mm in radius and about 0.30–0.35 g in weight.
These disks were washed several times with methanol