What happens to the silver ions in solution when the water is evaporated?
Silver ions in a solution cannot exist without water, so when the water is evaporated the silver ions (cations) must combine with an available anion to form a compound. The predominant anions present in a silver colloid solution are hydroxide and carbonate. The compounds thus formed are silver hydroxide and silver carbonate. Silver hydroxide is unstable and reduces to silver oxide and hydrogen. The silver carbonate will reduce to silver oxide and carbon dioxide. The final compound that remains is silver oxide. This process begins as a single silver ion is forced to combine with a single anion forming a single molecule of the compound. The molecule has no ionic charge and therefore no repulsive force. The lack of repulsion causes the molecules to be attracted to each other by van der Waals’ force of attraction which causes them to aggregate and form small particles of the compound. The size of the particle growth is limited by the reduced mobility of the molecules as the water evaporate
