posted on 2020-02-03, 20:03authored byAlexey Kamyshny, Jenny Gun, Dan Rizkov, Tamara Voitsekovski, Ovadia Lev
Polysulfides are abundant form of reduced sulfur
compounds whose distribution in aquatic systems continues
to pose environmental challenge. The Gibbs free-energy
of formation, enthalpy of formation, and standard entropy of
inorganic polysulfides were derived based on measurements
of the temperature-dependent distribution of inorganic
polysulfides in supersaturated aqueous polysulfide solutions.
The data complements the relevant Gibbs free-energy
data that were derived in our recent publication. The
thermodynamic data show that the average polysulfide
length is increased and polysulfides dissolve better at elevated
temperatures, though the extent of this increase is pH
dependent. At high pH (pH > 10) increasing the temperature
from 25 to 80 °C results in a 5.6% increase in the
concentration of polysulfide bound sulfur (i.e., dissolved
zerovalent sulfur) and increases the average chain length
(n̄) by 0.2 sulfur atoms, whereas at pH 8.2 the n̄ increases
by 0.25, and the dissolved polysulfide sulfur increases three-fold.