2. General physicochemical properties of hydrogen sulfide
Hydrogen sulfide is a colorless and highly toxic flammable gas, with its
unique odor being the smell of rotten eggs or the smell of decaying
sewage. Its molecular weight is 34.08, and its vapor density is heavier
than air, making it easier to diffuse at lower
points[17, 18]. As a binary weak acid,
hydrosulfuric acid is an aqueous solution of H2S that
can reach dissociation equilibrium at room temperature (25 ℃). The
solution concentration in a saturated state is
0.11mol.dm-3, and its pH value is approximately 4.0.
At 37 ℃ and pH 7.4, pK α 1=6.76, there is about 20%
H2S, 80% HS - and a small amount of
negligible S2- in extracellular
fluid[19]. At the same time, H2S
is also a small gas molecule with high lipophilicity, which allows it to
freely pass through the Lipid bilayer structure of the cell
membrane[20]. Hydrogen sulfide is a compound
similar to water molecules that can be oxidized into sulfur dioxide,
sulfate, thiosulfate, and elemental sulfur. In the body,
H2S can be oxidized to sulfates and thiosulfates, which
can be excreted in the urine. Some studies suggest that urinary
thiosulfates can serve as one of the biomarkers of hydrogen sulfide
poisoning[17, 21].