Scum, from soap

EDTA sequesters calcium and magnesium from hard water, preventing them from forming insoluble soap films (scum) with soaps and detergents. Chelators are sometimes used to sequester metal ions that interfere with dyes and perfumes. 

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

This is the type of substance responsible for bathtub rings. Before synthetic detergents were introduced for shampoos, some of the scum left over from soap would remain in people s hair after they washed it with soap. People would have to rinse their hair with vinegar to wash out the solid salts left over from the soap. 

Hard water contains Fe +, Ca +, and/or Mg + ions, all of which displace Na+ from soaps to form precipitates. This removes the soap from the water and puts an undesirable coating on the bathtub or on the fabric being laundered. Synthetic detergents are soap-like emulsifiers that contain sulfonate, —SOj, or sulfate, —OSOj, instead of carboxylate groups, —COO . They do not precipitate the ions of hard water, so they can be used in hard water as soap substitutes without forming undesirable scum. 

Another consideration of formulators is that consumers, as stated above, do not view products as being as neatly compartmentalized as manufactmers do. When a consumer wishes to clean a dirty bathtub, for example, they may have tried a cleanser, a dilutable APC, and a specialty spray soap scum ranover to do the job. All of these products are competing for the same job—cleaning soap scum from the bathtub surface. The consumer may use any or all of them to get the job done, according to their own personal standard of cleanliness, desire to apply elbow grease, and evaluation of the surface condition (new or worn, sensitive or impervious, etc.). 

Lyotropic Liquid Crystals From Soap Scum to Biological Membranes... 

Dendrimers, Fractals, Neurons, and Trees 769 Lyotropic Liquid Crystals From Soap Scum to Biological Membranes 774 Organic Surfaces Self-Assembling Monolayers and Langmuir-Blodgett Films 778 Free-Radical Living Polymerizations 787 Lycra/Spandex 790... 

As a detergent additive, it can also reactivate detergents or soaps that have combined with calcium to make an insoluble scum. The TSPP sequesters the calcium, replacing it with sodium, which reactivates the detergent or soap, and yet keeps the calcium from precipitating out of solution. 

Sodium carbonate is used in detergent formulas as a water softener, to lock up calcium and magnesium from the water. Calcium and magnesium would otherwise combine with the soap or detergents and form an insoluble scum that would stick to the clothes and the washing machine. 

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. 

Borax is used as a cleaning agent and water softener that removes ions of elements such as magnesium and calcium that cause hard water. When these hard water elements are mixed with soap, they prevent soap from sudsing and form a scum or residue that is deposited on hard surfaces. Borax can ehminate this residue ring by replacing the Mg and Ca ions with the more soluable Na and ions. Borax is the third most important boron compound. 

Hard" water contains impurities dissolved in it, such as chalk, and when ordinary soap is put into hard water, a precipitate, or scum, forms. This is not only unattractive, it is also wasteful, since it prevents the soap from doing its job until all the chemicals causing the scum have been pushed out of the water. One of the main chemical ingredients of hard water is calcium sulfate. 

Water from granite and other similar noncarbonate formations produce soft water, which has the benefit of lathering easily with soap, producing minimum scum or calcium stearate, calcium palmitate, etc. 

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. 

Soapless detergents Soap-like molecules which do not form a scum with hard water. These substances have been developed from petrochemicals. Their calcium and magnesium salts are water soluble and they are biodegradable. 

Soaps Substances formed by saponification. In this reaction, the oil or fat (glyceryl ester) is hydrolysed by aqueous sodium hydroxide to produce the sodium salt of the fatty acid, particularly sodium stearate (from stearic acid). Soap will dissolve grease because of the dual nature of the soap molecule. It has a hydrophobic part (the hydrocarbon chain) and a hydrophilic part (the ionic head) and so will involve itself with both grease and water molecules. However, it forms a scum with hard water by reacting with the Ca2+ (or Mg2+) present. 

Scum. It consists of the floatable materials skimmed from the surface of primary and secondary settling tanks. Scum may contain grease, oils, fats, waxes, soaps, hair, paper, cotton, and plastic materials that have specific gravity less than 1. 

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. 

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. 

Better cleaning products have been developed using chemicals derived from hydrocarbons. These synthetic detergents are carefully tailored to provide excellent cleaning power without the formation of scum. In most applications hydrocarbons derived cleaners have largely replaced soaps made from animal and plant products. Today 80% to 90% of the cleaning compounds used, both in the home and by industries, are based on chemicals derived from fossil fuel hydrocarbons. 

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