  We present a proof-of-concept study that dust extinction curves can be
extracted from the infrared (IR), optical, ultraviolet (UV) and X-ray afterglow
observations of GRBs without assuming known extinction laws. We focus on GRB
050525A (z = 0.606), for which we also present IR observations from the Spitzer
Space Telescope at about 2.3 days post-burst. We construct the spectral energy
distribution (SED) of the afterglow and use it to derive the dust extinction
curve of the host galaxy in 7 optical/UV wavebands. By comparing our derived
extinction curve to known templates, we see that the Galactic or Milky Way
extinction laws are disfavored versus the Small and Large Magellanic Cloud (SMC
and LMC) ones, but that we cannot rule out the presence of a LMC-like 2175
angstrom bump in our extinction curve. The dust-to-gas ratio present within the
host galaxy of GRB 050525A is similar to that found in the LMC, while about 10
to 40% more dust is required if the SMC template is assumed. Our method is
useful to observatories that are capable of simultaneously observing GRB
afterglows in multiple wavebands from the IR to the X-ray.
