Soap scum

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Soap scum or lime soap is the white solid composed of calcium stearate, magnesium stearate, and similar alkaline earth metal derivatives of fatty acids. These materials result from the addition of soap and other anionic surfactants to hard water. Hard water contains calcium and magnesium ions, which react with the surfactant anion to give these metallic or lime soaps. [1]

2 C17H35COONa+ + Ca2+ → (C17H35COO)2Ca + 2 Na+

In this reaction, the sodium cation in soap is replaced by calcium to form calcium stearate.

Lime soaps build deposits on fibres, washing machines, and sinks. Synthetic surfactants are less susceptible to the effects of hard water. Most detergents contain builders that prevent the formation of lime soaps.

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<span class="mw-page-title-main">Alkaline earth metal</span> Group of chemical elements

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<span class="mw-page-title-main">Calcium oxide</span> Chemical compound of calcium

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<span class="mw-page-title-main">Sodium carbonate</span> Chemical compound

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<span class="mw-page-title-main">Magnesium stearate</span> Chemical compound

Magnesium stearate is the chemical compound with the formula Mg(C
18
H
35
O
2
)
2
. It is a soap, consisting of salt containing two equivalents of stearate (the anion of stearic acid) and one magnesium cation (Mg2+). Magnesium stearate is a white, water-insoluble powder. Its applications exploit its softness, insolubility in many solvents, and low toxicity. It is used as a release agent and as a component or lubricant in the production of pharmaceuticals and cosmetics.

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Sodium stearate is the sodium salt of stearic acid. This white solid is the most common soap. It is found in many types of solid deodorants, rubbers, latex paints, and inks. It is also a component of some food additives and food flavorings.

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<span class="mw-page-title-main">Calcium stearate</span> Chemical compound

Calcium stearate is a carboxylate salt of calcium, classified as a calcium soap. The salt is a component of some lubricants, surfactants, as well as many foodstuffs. It is a white waxy powder.

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Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odor, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.

<span class="mw-page-title-main">Magnesium acetate</span> Chemical compound

Anhydrous magnesium acetate has the chemical formula Mg(C2H3O2)2 and in its hydrated form, magnesium acetate tetrahydrate, it has the chemical formula Mg(CH3COO)2 • 4H2O. In this compound magnesium has an oxidation state of 2+. Magnesium acetate is the magnesium salt of acetic acid. It is deliquescent and upon heating, it decomposes to form magnesium oxide. Magnesium acetate is commonly used as a source of magnesium in biological reactions.

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<span class="mw-page-title-main">Cobalt(II) stearate</span> Chemical compound

Cobalt(II) stearate is a metal-organic compound, a salt of cobalt and stearic acid with the chemical formula C
36
H
70
CoO
4
. The compound is classified as a metallic soap, i.e. a metal derivative of a fatty acid.

Nickel(II) stearate is a metal-organic compound, a salt of nickel and stearic acid with the chemical formula C
36
H
70
NiO
4
. The compound is classified as a metallic soap, i.e. a metal derivative of a fatty acid. The compound is harmful if swallowed and may cause skin sensitization.

Lead stearate is a metal-organic compound, a salt of lead and stearic acid with the chemical formula C
36
H
70
PbO
4
. The compound is classified as a metallic soap, i.e. a metal derivative of a fatty acid. The compound is toxic.

References

  1. Angelo Nora, Alfred Szczepanek, Gunther Koenen (2005). "Metallic Soaps". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a16_361.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)