  We document the similarities in composition between the equatorial basins Tui
Regio, Hotei Regio, and other 5-$\mu$m-bright materials, notably the north
polar evaporites, by investigating the presence and extent of an absorption
feature at 4.92 $\mu$m. In most observations, Woytchugga Lacuna, Ontario Lacus,
MacKay Lacus, deposits near Fensal, some of the lakes and dry lake beds south
of Ligeia, and the southern shores of Kraken Mare share the absorption feature
at 4.92 \um observed in the spectra of Tui and Hotei. Besides Woytchugga and at
Fensal, these 5-$\mu$m-bright deposits are geomorphologically-substantiated
evaporites. Thus, the similarity in composition strengthens the hypothesis that
Tui and Hotei once contained liquid. Other evaporite deposits, however, do not
show the 4.92 \um absorption, notably Muggel Lacus and the shores of Ligeia
Mare at the north pole. This difference in composition suggests that there are
more than one kind of soluble material in Titan's lakes that can create
evaporite and/or that the surface properties at the VIMS wavelength scale are
not uniform between the different deposits (crystal size, abundance, etc). Our
results indicate that the surface structure, composition, and formation history
of Titan's evaporites may be at least as dynamic and complex as their Earth
counterparts.
