  A single-lined spectroscopic orbit for the M giant in the X-ray binary IGR
J16194-2810 is determined from a time-series of optical spectra. The
spectroscopic orbital period of 192.5 days is twice that of the photometric
period, confirming that the M giant in the system is an ellipsoidal variable.
The giant is identified as a first ascent giant approaching the red giant tip.
The primary is a neutron star (NS) with its M giant companion filling its Roche
lobe verifying the system classification as a Low-Mass X-ray binary (LMXB).
Stellar C, N, O and Fe abundances are derived for the M giant with the C, N, O
values typical for a field giant with [Fe/H] = -0.14. The system does not have
a large kick velocity. Models for the evolution of the system into a binary
NS-white dwarf (WD) are presented. The X-ray properties are discussed in the
context of this model. This binary is a rare example of a luminous, long
orbital period, LMXB early in the transient ellipsoidal phase.
