Water fills the screen, hydrating the sodic clay particles until they repel one another and begin floating around the water as individual clay particles. A magnification bubble shows the layer of Na+ surrounding the clay particles swelling as the soil is hydrated to create a thick layer of positive charge around each particle. The scene is accompanied with the text 'As water is added to the dry sodic soil, Na+ is hydrated and the layer of positive charge gets wider until the clay particles begin to repel one another and disperse.'
The clay particles move through the water in a random motion as individual particles. This frame is accompanied with the text 'Random movement of clay particles further disperses them as the wide layer of positive charge repels other positive charged particles.'
The clay particles continue to move through the water in a random motion as individual particles. This frame is accompanied with the text 'If the width of the layer of positive charge can be decreased, we can control dispersion. The particles can get close together and attractive forces can take hold.'
This scene shows calcium ions (Ca2+) being added to the soil, replacing the Na+ ions with Ca2+ and decreasing the thickness of the layer of positive charge around each clay particle. A magnification bubble shows the thick layer of Na+ ions around a clay particle being replaced with Ca2+ ions and the thickness of the layer of positive charge decreasing. The scene is accompanied with the text 'Adding calcium (Ca2+) as gypsum to a sodic soil replaces Na+ with Ca2+ ions. This decreases the width of the layer of positive charge as one Ca2+ ion replaces two Na+ ions.'
The final scene shows the clay particles, now surrounded by a thin layer of positive charge of Ca2+ ions, aggregating and settling to the bottom of the water. The scene is accompanied with the text 'The thinner layer of positive charge means that attractive forces dominate repulsive forces, dispersion is controlled and aggregates reform.'