Adsorption Isotherms of Citric Acid Acting as a Growth‐Suppressor onto the (100) and (111) Faces of Sodium Chloride Crystals in Supersaturated Aqueous Solution

The growth‐starting supercooling Δ T G , a degree of supercooling at which a crystal starts to grow when the solution is continuously cooled, was measured in supersaturated aqueous solutions in the presence of citric acid as an impurity. It was measured both for the (100) and (111) faces of sodium chloride crystals. From the measured data of Δ T G , the Langmuir constants of the (100) and (111) faces were determined at pH = 4.5 to be 6.16 ± 0.88 L/mol and 12.5 ± 2.0 L/mol, respectively. This Δ T G method is a convenient method for the determination of adsorption isotherms of an impurity onto specific crystallographic faces of a crystal.