Comparison of the column density of the presented molecular species and N(H₂). Each colored symbol represents different individual clouds in the sightline toward the observed background continuum sources (DR2l: red X, G09.62+0.19: blue circle, G10.47 +0.03: green up-triangle, G19.61−0.23: cyan square, G29.96−0.02: yellow left-triangle, G31.41+0.31: lime hexagon, G32.80+0.19: magenta star, G45.07+0.13: orange cross, NGC 6334 I: black down-triangle, W3 IRS5: aquamarine thin diamond, W3(OH): light-coral pentagon, W43 MM1: dodger-blue octagon). Filled and unfilled markers indicate foreground components and molecular envelope components, respectively. For the molecular envelope components, only lower limits are marked by arrows instead of fitting uncertainty bars. Black diagonal dotted lines represent abundances of given molecules on the y-axis relative to N(H₂) with their values labeled. In each panel, two vertical blue dotted lines indicate the visual extinction of 1 and 5, respectively. In the plot of N(C₂H)/N(c-C₃H₂), the gray horizontal dashed line indicates a mean value of 30.26 in the column density ratio.