  The sulphur chemistry in nine regions in the earliest stages of high-mass
star formation is studied through single-dish submillimeter spectroscopy. The
line profiles indicate that 10-50% of the SO and SO2 emission arises in
high-velocity gas, either infalling or outflowing. For the low-velocity gas,
excitation temperatures are 25 K for H2S, 50 K for SO, H2CS, NS and HCS+, and
100 K for OCS and SO2, indicating that most observed emission traces the outer
parts (T<100 K) of the molecular envelopes, except high-excitation OCS and SO2
lines. Abundances in the outer envelopes, calculated with a Monte Carlo
program, using the physical structures of the sources derived from previous
submillimeter continuum and CS line data, are ~10^-8 for OCS, ~10^-9 for H2S,
H2CS, SO and SO2, and ~10^-10 for HCS+ and NS. In the inner envelopes (T>100 K)
of six sources, the SO2 abundance is enhanced by factors of ~100-1000. This
region of hot, abundant SO2 has been seen before in infrared absorption, and
must be small, <~ 0.2 arcsec (180 AU radius). The derived abundance profiles
are consistent with models of envelope chemistry which invoke ice evaporation
at T~100$ K. Shock chemistry is unlikely to contribute. A major sulphur carrier
in the ices is probably OCS, not H2S as most models assume. The
source-to-source abundance variations of most molecules by factors of ~10 do
not correlate with previous systematic tracers of envelope heating. Without
observations of H2S and SO lines probing warm (>~ 100 K) gas, sulphur-bearing
molecules cannot be used as evolutionary tracers during star formation.
