We will use the SWS, LWS, and ISOPHOT instruments to determine the
 nature of the cold material in cooling flow clusters of galaxies.
 X-ray  spectra indicate that very large fluxes of soft X-rays are
 being absorbed by some cold component of the intracluster medium.
 The X-ray absorbing cold material may have a mass of 10e11-10e12
 Msun and thus be the ultimate repository of the cooling flow.
 Yet, this cold component has yet to be identified or
 verified by observations in any other spectral band.
 In particular, the energy absorbed as X-ray. about 3x10^43 erg/s,
 must re-emerge in another spectral band, and this cooling emission
 from the cold gas has yet to be observed.  The best present models
 indicate that the cold gas must primarily emit in the FIR.
 If the gas is relatively dust-free, the primary emission should
 be in lines of [C I], [C II], [O I], and [Si II].  If the
 cold material is very dusty, the bulk of the emission might be dust
 radiated FIR continuum.  We will compare the ROSAT and ASCA
 spatially resolved X-ray spectra from the clusters with spatially
 resolved FIR spectra in [C II] (158 mu), [O I] (63 mu), and
 [Si II] (35 mu),and broad-band photometry from 60 to 200 microns.
 Either we will strongly detect this emission, or the existence of
 this cold gas will be placed in great doubt.  Assuming we do
 detect the emission, this data will allow us to determine the
 density, temperature and total mass of the absorbing gas, and the
 role of dust in the X-ray absorption and energetics of the cool
 gas.  By looking at a sample of 10 clusters, we can determine the
 relationship of this cold gas to the X-ray emitting hot gas,
 the overall properties of the clusters, and the properties of the
 central galaxy and its nuclear activity.