This paper presents spectra in the 2 to 20 µm range of quiescent cloud material located in the IC 5146 cloud complex .
The spectra were obtained with NASA ’ s Infrared Telescope Facility ( IRTF ) SpeX instrument and the Spitzer Space Telescope ’ s Infrared Spectrometer .
We use these spectra to investigate dust and ice absorption features in pristine regions of the cloud that are unaltered by embedded stars .
We find that the H _ { 2 } O-ice threshold extinction is 4.03 \pm 0.05 mag .
Once foreground extinction is taken into account , however , the threshold drops to 3.2 mag , equivalent to that found for the Taurus dark cloud , generally assumed to be the touchstone quiescent cloud against which all other dense cloud and embedded young stellar object observations are compared .
Substructure in the trough of the silicate band for two sources is attributed to CH _ { 3 } OHÂ and NH _ { 3 } Â in the ices , present at the \sim 2 % and \sim 5 % levels , respectively , relative to H _ { 2 } O-ice .
The correlation of the silicate feature with the E ( J - K ) color excess is found to follow a much shallower slope relative to lines of sight that probe diffuse clouds , supporting the previous results by Chiar et al. ( 2007 ) .