What question did this study set out to answer?

The aim is to quantify the partial molar volumes of salts and their constituent ions using solution density.

April 3, 2026Inorganic Chemistry0 citations

Solvation Ion Volumes from Solution Densities

ODOrin R. DaspitCalvin University MGMagdalene A. GrabillCalvin University ABAerin E. BakerCalvin University

Key Points

The aim is to quantify the partial molar volumes of salts and their constituent ions using solution density.
Analyzed the initial slope of solution density versus molarity.
Quantified the partial molar volumes of 48 different salts.
Deconvoluted salt volumes into the volumes of 24 constituent ions.
Calculated uncertainty ranges for the measured volumes.
Partial molar volumes found to be higher than previously reported.
Specific ion volumes measured include sodium (4.0 ± 0.2 mL/mol) and ammonium (23.2 ± 0.3 mL/mol).
Nitrate, acetate, and chloride also measured with similar precision.

Abstract

Aqueous ion volumes are as useful as they are tricky to quantify. By focusing on the initial slope of solution density versus molarity─an uncommon approach─the partial molar volumes of 48 salts have been reliably quantified, along with uncertainty ranges, and found to be higher than previously reported. Deconvoluting these salt volumes into the volumes of their 24 constituent ions leads to a reliable list of ion volumes in aqueous solution. Specific values (mL/mol) include sodium (4.0 ± 0.2), ammonium (23.2 ± 0.3), nitrate (22.8 ± 0.4), acetate (37.5 ± 0.5), and chloride (12.6 ± 0.2). This work could readily be extended to include even more ions since ultimately it depends on elementary lab technique and careful data analysis.

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