  We present and validate a new network of atmospheric thermo-chemical and
photo-chemical sulfur reactions. We use a 1-D chemical kinetics model to
investigate these reactions as part of a broader HCNO chemical network in a
series of hot and warm Jupiters. We find that temperatures approaching
$1400\,\mathrm{K}$ are favourable for the production of H2S and HS around
$\mathrm{10^{-3}\,bar}$, the atmospheric level where detection by transit
spectroscopy may be possible, leading to mixing ratios of around $10^{-6}$. At
lower temperatures, down to $1000\,\mathrm{K}$, the abundance of S2 can be up
to a mixing ratio of $10^{-5}$ at the same pressure, at the expense of H2S and
HS, which are depleted down to a mixing ratio of $10^{-6}$. We also investigate
how the inclusion of sulfur can manifest in an atmosphere indirectly, by its
effect on the abundance of non-sulfur-bearing species. We find that in a model
of the atmosphere of HD 209458 b, the inclusion of sulfur can lower the
abundance of NH3, CH4 and HCN by up to two orders of magnitude around
$\mathrm{10^{-3}\,bar}$. In the atmosphere of the warm Jupiter 51 Eri b, we
additionally find the inclusion of sulphur depletes the peak abundance of CO2
by a factor of five, qualitatively consistent with prior models. We note that
many of the reactions used in the network have poorly determined rates,
especially at higher temperatures. To obtain a truly accurate idea of the
impact of sulfur chemistry in hot and warm Jupiter atmospheres, new
measurements of these reaction rates must take place.
