The purpose of this proposal is to search for the infrared signature of
graphite dust in the interstellar medium, to resolve the currently still
questionable origin of the 2200 angstrom extinction feature. Graphite has been
suggested as an interstellar dust component, since it  posseses a strong
absorption peak at 2200 A, which is a prominent  observed feature in the
interstellar extinction curve.  However, except for this feature, there has
been no other major reasons to adopt graphite as an interstellar dust
constituent. Furthermore,  other candidate material, such as standard coal or
polycyclic aromatic  hydrocarbons (PAHs), have strong absorption features at
2200 A, and can also  be potential carriers of this feature.  As a result,
despite 30 years of continuing research, the identification of  the 2200 A
feature is still controversial. However, ISO is uniquely capable of resolving
this issue, since graphite is distinguished from  other candidate material by
the presence of two  infrared-active resonances at 11.52 and 6.30 microns
(Draine 1984, ApJ, 277,  L71). Of the two, the 11.52 feature is the stronger
one. We therefore propose to search for the feature in absorption along the
line of sight of a heavily obscured (in the visible) bright source at infrared
wavelengths.