Chlorine isotopic ratio, [H³⁵Cl]/[H³⁷Cl], as a function of galac-tocentric radius. The ratio is derived using two methods: R₁, which is based on derived XCLASS column densities (for both core and outflow components), and R₂, using integrated line intensity ratios. R₁ results are further divided into emission and absorption components. Grey symbols indicate the ³⁵Cl/³⁷Cl ratio from previous studies of (a) HCl Peng et al. (2010, pentagons), Cernicharo et al. (2010, octagon), Lis et al. (2010, diamond), and, (b) H₂Cl⁺, Neufeld et al. (2015, white-faced octagon). For context, the Solar System value (3.13; Lodders et al. 2009) and Galactic chemical evolution model predictions for varying metallicities (Kobayashi et al. 2011) are shown using horizontal lines.