Soap scum

Anionic surfactants are the most commonly used class of surfactant. Anionic surfactants include sulfates such as sodium alkylsulfate and the homologous ethoxylated versions and sulfonates, eg, sodium alkylglycerol ether sulfonate and sodium cocoyl isethionate. Nonionic surfactants are commonly used at low levels ( 1 2%) to reduce soap scum formation of the product, especially in hard water. These nonionic surfactants are usually ethoxylated fatty materials, such as H0CH2CH20(CH2CH20) R. These are commonly based on triglycerides or fatty alcohols. Amphoteric surfactants, such as cocamidopropyl betaine and cocoamphoacetate, are more recent surfactants in the bar soap area and are typically used at low levels (<2%) as secondary surfactants. These materials can have a dramatic impact on both the lathering and mildness of products (26). 

Tetrasodium etidronate is used as a water softener in soaps to prevent soap scum and bathtub rings by locking up the calcium and magnesium in the water. 

Pentasodium pentetate, tetrasodium etidronate, and tetra-sodium EDTA are added as water softeners and to protect the dyes and perfumes from the effects of metal ions in the mixtures. These compounds lock up calcium and magnesium in the water, preventing them from reacting with the soap to form insoluble soap scum. 

Figure 5.3 As seen on the side of the tub and drain stopper right), a white residue known as soap scum forms when soap reacts with calcium salts present in hard water.

Question 5.12 Why Does Soap Scum Form Why Are Phosphates in Detergents 53... 

Choose acidic formulations for products designed to dissolve soap scum, hard water spots, stains, rust, or encrustations that are mainly calcium or magnesium salts [10]. 

Soap works because the nonpolar end dissolves in dirt (oil), leaving the polar end outside the dirt. This combination is known as a micelle (see Figure 16-30). To the surrounding water molecules, the micelle appears as a very large ion. These ions tire water-soluble and repel each other due to their like charges, a behavior that causes them to remain separated. Metal ions in hcird water (Ca VMg VFe ) cause a precipitate to form because they react with carboxylate ions to form an insoluble material (also known as the soap scum hanging around the bathtub or shower). 

Removes mildew stains and soap scum effectively by prolonging contact time... 

Hard Foaming Hard Surface Cleaner for Soap Scum Removal... 

This formula produces a copious, dense foam. It is suitable for cleaning soap scum from shower stall tiles and other bathroom and household fixtures. 

Sometimes people refer to water as being "hard" or "soft." If someone says water is hard, he means that there are a lot of calcium (Ca2+) or magnesium (Mg2+) ions dissolved in it. Hard water causes several problems. First, it can cause scales to form on the inside of pipes, water heaters, or teakettles. These scales occur when the calcium or magnesium precipitates out of solution and sticks to the insides of pipes. The scales build up and eventually the pipes are completely clogged. Hard water also prevents soap from lathering, and it reacts with soap to leave behind a sticky film commonly called soap scum. 

There are two solutions to soften water that is too hard. First, the water could be filtered to remove all of the calcium and magnesium ions. But this can be very expensive, so most people use a water softener instead. A water softener is a piece of equipment that can be attached to the water pipes that run into a house. This way, all the household water goes through the water softener before going into the other pipes in the house. Inside a water softener are small plastic beads. These beads have sodium ions (Na+) stuck on them. As the water flows over the bed of beads, the magnesium and calcium ions get replaced with the sodium ions. Since sodium is easily dissolved in water, it does not precipitate out in pipes like calcium and magnesium ions do. As a result, no scales form inside the pipes. Sodium ions do not react with soap to form soap scum, either, and they allow the soap to lather properly. 

SDS has several advantages over soap. Unlike the carboxylate anions in soap, the dodecylsulfate anion does not form insoluble precipitates with hard water ions (e.g., Ca2+), leading to the formation of soap scum. Also, the dodecylsulfate anion is the conjugate base of a very strong acid (H2S04). Therefore, SDS is a weak base, and solutions of SDS are pH neutral. 

A soap is the sodium salt of carboxylic acid attached to a long, nonpolar hydrocarbon chain. When a soap is placed in hard water, the sodium cations exchange with cations such as Ca2+ and Mg2+. The resulting calcium and magnesium salts are insoluble in water and precipitate to form soap scum. ... 

Such a molecule can cause particles of grease or oil to mix somewhat with water and to be washed from a dirty article. Calcium and magnesium ions in hard water react with stearate ions to form a solid, yielding soap scum. To avoid this problem, chemists developed synthetic detergents that do not form insoluble salts with calcium and magnesium ions. Synthetic detergents are similar to soaps in that they have an ionic end and a large hydrocarbon-like end. 

Eliminate soap scumming or hard water precipitates... 

Another common precipitation product is soap scum. Soap scum generally floats on water rather than raining out, so it is normally not thought of as a precipitate—but that is a matter of semantics. Scum can form in bathtubs when soap mixes with hard water that is, water that contains calcium and magnesium ions. Water that contains calcium and magnesium ions is called hard because these ions tend to form insoluble precipitates (that is, little rocks) in the water. 

Figure 3 Minerals and soap react to form soap scum, which comes out of the water solution and coats the tiles of a shower.

Forming Solids from Solutions Under certain conditions, a solute can come back out of its solution and form a solid. This process is called crystallization. Sometimes this occurs when the solution is cooled or when some of the solvent evaporates. Crystallization is the result of a physical change. When some solutions are mixed, a chemical reaction occurs, forming a solid. This solid is called a precipitate (prih SIH pub tayt). A precipitate is the result of a chemical change. Precipitates probably have formed in your sink or shower because of chemical reactions. Minerals that are dissolved in tap water react chemically with soap. The product of this reaction leaves the water as a precipitate called soap scum, shown in Figure 3. 

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