Speed of Sound in Aqueous and Methanolic Lithium Nitrate Solutions

Speeds of sound in aqueous and methanolic lithium nitrate solutions were measured as functions of concentration (0.0181 ≤ m/(mol·kg-1) ≤ 21.818) and temperature (273.15 ≤ T/K ≤ 323.15) at 2 MHz. The isentropic compressibility isotherms for aqueous lithium nitrate solutions converge at 3.75 mol·kg-1, and at this concentration the primary hydration shell of the solute has become just saturated. It has been estimated that there are 15 molecules of water in the primary hydration shell of lithium nitrate, and the calculated primary hydration number of the nitrate ion was found to be 9. For methanolic lithium nitrate solutions, the isentropic compressibility isotherms vary smoothly within the concentration and temperature ranges of study.