which brand of soap is best to use in soft water?”
This is a chemistry question that requires a chemical answer. There are many ‘common sense’ answers that don’t do the problem justice. First, soap is made by heating animal fat (triglyceride fats) with lye (sodium hydroxide). The lye (NaOH) gives up its OH group and separates the glycerine from its three fatty acid molecules. This produces one molecule of glycerol and three ionically-bonded molecules of sodium stearate (soap). This sodium salt will give up its sodium ion to a water solution. The stearate will subsequently precipitate if it comes in contact with an ion that wants to hold on to it more strongly. Calcium and magnesium are the usual culprits when ‘hard water’ is used in the shower. The resulting calcium and/or magnesium stearate make the ever- popular ‘bathtub ring’. Sodium stearate (soap) is comprised of a single sodium ion attached to a single stearate ion. This combination is soluble. Calcium and magnesium each have two places to form bonds and each of these metallic io
