It is also H2S and more complicated sulphur compounds called
mercaptans which provide part of the delightful odour of sewage
and rotting organic materials like flesh..
Hello John. Yes, protein is composed of alpha amino acids three of
which contain sulfur (cysteine, methionine and cystine).
Decomposition of these compounds does produce hydrogen sulfide as
you point out. However, I thought you might like to know that the
main culprits causing horrific odors in rotting flesh are the
amines. Scatole and indole are bicyclic amines which endow the old
out houses with their distinctive aroma. The worse offenders are
the diamines. Examples are “cadavarine” (2HN(CH2)5NH2) and
"putrascene" (2HN(CH2)4NH2). I am sure you really wanted to know
that, but that is not the reason I felt I needed to write this post.
The reason is a characteristic of hydrogen sulfide that I don’t
believe many folks are aware of. Almost everyone knows that the gas
is extremely toxic, but how many know that the sense of smell is
lost after 2 - 15 minutes exposure to hydrogen sulfide? No rotten
egg odor to remind you need fresh air. The gas is toxic at 10 ppm.
OSHA has a ceiling of 20 ppm on it. Exposure to concentrations of
700-800 ppm or greater usually results in death. The gas is quite
flammable. It has a flash point of -82 deg. C and an autoignition
temperature of 260 deg. C. The explosive limits are 4.3% to 46%.
The annoyance of the rotten egg odor is not the only reason adequate
ventilation is needed when working with hydrogen sulfide. I don’t
believe that anybody will get in trouble heating a small amount of
ammonium sulfide on a piece. But, it might be a different story if
they have many pieces to do.
"Marlinespike Seamanship in Precious Metals"