Composition of the Interstellar Medium

We present an analysis of the Fe II, Ge II, Mg I, Mg II, S I, S II, Si II and Zn II interstellar lines for 63 stars. The column density of Mg II, S II, Si II and Zn II is well correlated with the distance. However, the column density -- distance relation should be used with care for the estimation of the distance to OB stars. For stars with large $f(H_2)$ this relation can lead to a large overestimation of the distance. Hydrogen -- normalised column densities of Mg II, Si II and Ge II (our largest samples of data) drop with the interstellar reddening E(B-V) as expected for elements that are incorporated into dust grains. The Ge II abundance (GeII/H) is lower in dense molecular clouds. The abundances of all analysed elements are generally lower than their Solar System values.

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