  We present a new technique for determining the *quantity and composition* of
dust in astrophysical environments using <6keV X-rays. We argue that high
resolution X-ray spectra as enabled by the Chandra and XMM-Newton gratings
should be considered a powerful and viable new resource for delving into a
relatively unexplored regime for directly determining dust properties:
composition, quantity, and distribution. We present initial cross-section
measurements of astrophysically likely iron-based dust candidates taken at the
Lawrence Berkeley National Laboratory Advanced Light Source synchrotron
beamline, as an illustrative tool for the formulation of our methodology.
Focused at the 700eV Fe LIII and LII photoelectric edges, we discuss a
technique for modeling dust properties in the soft X-rays using L-edge data, to
complement K-edge X-ray absorption fine structure analysis techniques discussed
in Lee & Ravel 2005. This is intended to be *a techniques paper* of interest
and usefulness to both condensed matter experimentalists and astrophysicists.
For the experimentalists, we offer a new prescription for normalizing
relatively low S/N L-edge cross section measurements. For astrophysics
interests, we discuss the use of X-ray absorption spectra for determining dust
composition in cold and ionized astrophysical environments, and a new method
for determining *species-specific gas-to-dust ratios*. Possible astrophysical
applications of interest, are offered. Prospects for improving on this work
with future X-ray missions with higher throughput and spectral resolution are
presented in the context of spectral resolution goals for gratings and
calorimeters, for proposed and planned missions such as Astro-H and the
International X-ray Observatory.
