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The solid carbon monoxide (CO) feature at 4.67 $\mu$m gives a spectroscopic signature of dust in the coldest regimes of dense molecular clouds. Field stars provide an important means for probing molecular clouds where icy mantles are most likely to form. Combining observations of field stars with those of protostars allows a comparison of the extent of grain processing in protostellar environments to be made. High resolution data taken at UKIRT for the Taurus dark cloud enables us to fit laboratory mixtures to the solid CO data. These data present strong new evidence for the presence of carbon dioxide (CO$_2$) in the grain mantles around the embedded objects.
The long-wavelength wing of the water-ice feature (between 3.2 and 3.6 $\mu$m) contains the C-H stretching vibrations in carbon-bearing molecules. Using CGS 4 on UKIRT, we have observed the 3 $\mu$m spectral region in embedded objects and heavily obscured field stars in Taurus. In our preliminary analysis, we find little evidence of the 3.54 $\mu$m methanol (CH$_3$OH) feature in any of these sources. These non-detections are significant and suggest that CH$_3$OH might not be widespread in molecular clouds but restricted to processed regions around protostars. It is important to understand why the methanol feature has only been detected towards the very luminous protostars observed by other groups.
