A speciation study of sulfur(iv) in aqueous solution.

Area of Science:

• Analytical Chemistry
• Environmental Chemistry
• Inorganic Chemistry

Background:

• Understanding sulfur dioxide (S(iv)) speciation is crucial for environmental and industrial processes.
• Previous studies have limitations in accurately determining S(iv) species across a wide pH range.
• Accurate speciation data informs environmental modeling and chemical process optimization.

Purpose of the Study:

• To comprehensively determine the speciation of S(iv) in aqueous solutions.
• To accurately quantify the dimerisation constant for disulfite formation.
• To identify and quantify protonated disulfite species for the first time.

Main Methods:

• Ultraviolet spectrophotometric titrations were employed.
• Global analysis of the entire spectral dataset was performed.
• Measurements covered a wide pH range (9.6 to 1).

Main Results:

• The dimerisation constant for disulfite formation from hydrogen sulfite was accurately determined.
• Protonated disulfite was identified and quantified for the first time.
• Molar absorptivities for all S(iv) species were reported across the studied wavelength range.

Conclusions:

• This research provides a complete speciation profile of S(iv) in aqueous solutions.
• The accurate determination of the dimerisation constant and identification of protonated disulfite advance the understanding of sulfur chemistry.
• The reported molar absorptivities enable more precise quantitative analysis of S(iv) species.