Soap scum
Encyclopedia
Soap scum is an informal term for the white solid that results from the addition of soap
to hard water
. Hard water contains calcium
or magnesium
ions, which react with the fatty acid component of soap to give what are technically called lime soaps:
In this reaction, the sodium
ion in soap is replaced by calcium ions.
Lime soaps are ineffective in washing dishes or clothes or hair. Thus, hard water needs large amounts of soap to form a lather, and in hair washing the soap scum sticks in the hair. Synthetic detergents are less susceptible to the effects of hard water.
Although soap scum is generally considered a nuisance, its components, calcium stearate
and magnesium stearate
when produced intentionally, are very useful materials in the polymer industry and in pharmaceutical industry.
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...
to hard water
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...
. Hard water contains calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
or magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
ions, which react with the fatty acid component of soap to give what are technically called lime soaps:
- 2 C17H35COO-Na+ + Ca2+ → (C17H35COO)2Ca + 2 Na+
In this reaction, the sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
ion in soap is replaced by calcium ions.
Lime soaps are ineffective in washing dishes or clothes or hair. Thus, hard water needs large amounts of soap to form a lather, and in hair washing the soap scum sticks in the hair. Synthetic detergents are less susceptible to the effects of hard water.
Although soap scum is generally considered a nuisance, its components, calcium stearate
Calcium stearate
Calcium stearate is carboxylate of calcium that is found in some lubricants and surfactants. It is a white waxy powder.-Production and occurrence:Calcium stearate is produced by heating stearic acid, a fatty acid, and calcium oxide:...
and magnesium stearate
Magnesium stearate
Magnesium stearate, also called octadecanoic acid, magnesium salt, is a white substance which is solid at room temperature. It has the chemical formula . It is a salt containing two equivalents of stearate and one magnesium cation...
when produced intentionally, are very useful materials in the polymer industry and in pharmaceutical industry.