Teachers should verify their own results prior to the use of these lesson plans in a classroom setting. Safety glasses or goggles should be worn at all times. Other protective clothing should be worn as instructed by the teacher. All materials should be properly disposed of as instructed by the teacher. Certain metal ions, particularly those with double and triple charges, interfere with the ability of soap to make suds.
Hard water causes soap to precipitate, as evidenced by a bathtub ring.
Calcium, magnesium, and iron ions are commonly found in hard water. Detergents have largely replaced laundry soap because of their ability to make suds in hard water. However, even detergents are affected by the presence of multicharged cations. Ligands are molecules or ions that can bond to cations by donating a pair of electrons. They are particularly effective at forming complexes with multicharged cations.