Solubility of different salts used in the control of the water activity of foods

Solubilidade de diferentes sais usados ​​no controle da atividade de água de alimentos

ABSTRACT

Saturated salt solutions produce environments with specific relative humidities used in several applications, such as determining water sorption isotherms of foods. However, the preparation of saturated solutions requires knowledge of solubility data. Thus, the objective of this work was to determine the solubility of 14 salts: lithium bromide (LiBr), lithium chloride (LiCl), lithium iodide (LiI), magnesium chloride (MgCl₂), sodium iodide (NaI), potassium carbonate (K₂CO₃), magnesium nitrate (Mg(NO₃)₂), sodium bromide (NaBr), potassium iodide (KI), sodium chloride (NaCl), ammonium sulfate ((NH₄)₂SO₄), potassium chloride (KCl), potassium nitrate (KNO₃), and potassium sulfate (K₂SO₄) in the temperature range of 275.15 to 363.15 K at 101.3 kPa. The apparatus for the solubility determination consists of a jacketed glass cell and a magnetic stirrer. Furthermore, polynomial and exponential empirical models were fitted to the observed data to determine salt solubilities. Salt solubilities ranged from 7.39 to 80.41 g of salt·(100 g of solution)^-1. Sodium iodide (NaI) presented the highest (p<0.05) solubility, up to 343.15 K, and lithium iodide (LiI) up to 363.15 K. The specific equilibrium moistures afforded by saturated saline solutions were associated with water activity data. A general mathematical model to determine the solubility of different salts was not obtained because the dissolution behaviors of each salt are distinct. However, the availability of solubility data of saline solutions covering a wide range of temperatures is helpful since the salts have different behavior.

Index terms: Gravimetric method; exponential model; polynomial model; saturation; temperature.