Registration Dossier
Registration Dossier
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EC number: 231-977-3 | CAS number: 7783-06-4
Hydrolysis
Administrative data
Link to relevant study record(s)
Description of key information
Up to a limit concentration H2S dissolves in water rapidly and easily in
a temperature dependent way. At 20 °C the limit is 3.98 g/l. H2S can
stay present in water for several hours.
H2S + H2O --> HS- + H3O+ (pKa1 = 7.04)
HS- + H2O --> S2- + H3O+ (pKa2 = 11.96)
In aqueous environments, H2S and the correponding salts, Na2S and NaHS,
are easily dissolved and immediately hydrolyzed and, as a function of
pH, an equilibrium is established between S2-, HS-, and H2S, with
increasing H2S formation at decreasing pH. Temperature and salinity also
affect this equilibrium but to a much lesser extent than pH.
Na2S + H2S --> NaHS + NaOH
NaHS + H2O --> NaOH + H2S
Key value for chemical safety assessment
Additional information
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