Abundances of CS and SiS with uncertainties for the carbon-rich stars (left panel), the S-type stars (right panel), and including H 2 S abundances from Danilovich et al. (2017 assuming an ortho-to-para ratio of three) for the oxygen-rich stars (middle panel). Fractional abundances relative to H2 are given by the left vertical axis and mass-loss rates are indicated by the black stars and the right vertical axis. The dashed, grey, horizontal line represents the maximum sulphur abundance expected based on the Asplund et al. (2009) solar abundance.