HCL ABSORPTION TOWARD SAGITTARIUS B2

We have detected the 626 GHz J = 1 --> 0 transition of hydrogen chlori de ((HCl)-Cl-35) in absorption against the dust continuum emission of the molecular cloud Sagittarius B2. The observed line shape is consist ent with the blending of the three hyperfine components of this transi tion by the velocity profile of Sgr B2 observed in other species. The apparent optical depth of the line is tau approximate to 1, and the mi nimum HCl column density is 1.6 x 10(14) cm(-2). A detailed radiative transfer model was constructed which includes collisional and radiativ e excitation, absorption and emission by dust, and the radial variatio n of temperature and density. Good agreement between the model and the data is obtained for HCl/H-2 similar to 1.1 x 10(-9). Comparison of t his result to chemical models indicates that the depletion factor of g as-phase chlorine is between 50-180 in the molecular envelope surround ing the SgrB2(N) and (M) dust cores.