Hydration Numbers of Non-Electrolytes in Aqueous Solvents of Fixed pH

Abstract

In the present article the applicability of the Pasynski method of determination of hydration numbers of simple organic compounds in aqueous solvents of fixed pH at 25 • C from speed-of-sound and density measurements is tested and discussed. It was shown that for solutes which do not undergo protolytic reactions with a solvent the resulting values of hydration numbers are independent on the system pH-for these solutes n h can be determined both in pure aqueous solutions and in mixtures containing ions. For solutes which undergo reactions with an acid or base, the Pasynski method yields hydration numbers which are a combination of compressibilities of substrates and products of occurring reactions.

Hydration of Amino Acids from Ultrasonic Measurements

“…Such a simple arithmetic analysis explains very well the observed values of the hydration numbers and leads to calculated n h values very close to the experimental ones. This was also recently proved by us for reacting systems such as amines in acidic and carboxylic acids in alkaline solutions …”

Hydration Numbers of Nonelectrolytes from Acoustic Methods

“…This method was used for determining hydration numbers of polymers, including poly(ethylene glycol)s and poly(vinyl alcohol)s, − carbohydrates and their derivates, ,− sweeteners, , alcohols, glycols, carboxylic acids and amines, − ethanolamines, amino acids, − ,− and albumins of the human serum and hen egg …”

Effects of Alkaline Earth Metal Ions on Thermodynamic and Ultrasonic Properties of Ascorbic Acid

“…Another parameter studied was solvation number , ( S n ), obtained by eq S normalN = ( n 1 / n 2 ) ( 1 − κ s / κ s 0 ) Where n 1 and n 2 are the numbers of moles of the solvent and the solute and κ s and κ s 0 are compressibility coefficients of the solution and the pure solvent. Considerably high solvation numbers (Table ) obtained especially at low solute concentrations and at low temperatures indicate either strong electrostriction around the chloride ions and/or cation electrostrictive interaction exceeding the first solvation shell .…”

“…R and W were increasing linearly with electrolyte molality (Figures 5 and 6) indicating the solute−solvent interactions in the system. 31 Another parameter studied was solvation number 32,33 (S n ), obtained by eq 14…”