1. Chemistry for Changing Times 12th Edition Hill and Kolb
Chapter 21
Household Chemicals:
Helps and Hazards
John Singer
Jackson Community College, Jackson, MI
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History of Cleaning
Many years ago and even today in the third world, clothes are cleaned by beating on rocks in a river or stream. Some plants such as soapworts or soapberries contain saponins, which produce a soapy lather. Wood ashes contain potassium and sodium carbonate, which form alkaline solutions in water with some detergent properties. Sodium carbonate is still sold today as washing soda.
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Fat + Lye → Soap
Soap is made by reacting animal fat or vegetable oil with lye (NaOH).
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Fat + Lye → Soap
Soap works because one end of the molecule is hydrophilic (water attracting) and the other end is hydrophobic (water repelling).
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Fat + Lye → Soap
The hydrophobic “tail” dissolves into oil, leaving the hydrophilic “head” on the outside. This spherical structure is called a micelle.
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Fat + Lye → Soap
Oil and water form an emulsion, with the soap acting as the emulsifying agent. Any substance, such as soap, that stabilizes the suspension of nonpolar substances in water is called a surfactant (surface-active) agent.
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Fat + Lye → Soap
Disadvantage of Soap
Water that contains calcium, magnesium, and iron ions is called hard water. These ions will react with and precipitate soap, reducing its effectiveness.
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Fat + Lye → Soap
Water Softeners
Additives such as washing soda (Na2CO H2O) and trisodium phosphate (TSP = Na3PO4) will raise the pH of water and precipitate calcium and magnesium ions.
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Fat + Lye → Soap
Water Softeners
Water softening tanks are also used in homes and businesses. They contain a polymeric material that hold the calcium, magnesium, and iron ions and exchange them with sodium ions.
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Synthetic Detergents
During World War II, the raw materials for soap production became scarce. Synthetic detergents were developed with cleansing action similar to soap, but without the negative effects of hard water.
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Synthetic Detergents
ABS Detergents: Nonbiodegradable
The first synthetic detergents were alkylbenzenesulfonates (ABS) detergents. Unfortunately, they are nonbiodegradable and produced a foam that appeared on natural lakes and rivers as well as in wells and sewage treatment plants. ABS detergents were banned and replaced by biodegradable detergents.
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Synthetic Detergents
ABS Detergents: Nonbiodegradable
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Synthetic Detergents
LAS Detergents: Biodegradable
Linear alkylsufonates (LAS) detergents have linear chains of carbon atoms that can be broken down by microorganisms.
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14. Laundry Detergent Formulations
Laundry detergents contain a variety of compounds designed for specific functions. These compounds are classified as surfactants, builders, and brighteners.
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15. Laundry Detergent Formulations
Surfactants emulsify the soil and oils. They can be either anionic, cationic, nonionic or amphoteric.
Amphoteric surfactants carry both a positive and negative charge on the same molecule. A betaine is an example of an amphoteric surfactant.
CH3(CH2)nCH2NH2+CH2COO-
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16. Laundry Detergent Formulations
Builders are added to detergent formulas to increase the detergency of the surfactant. Examples include sodium citrate (Na3C6H5O7), sodium tripolyphosphate (Na5P3O10), and sodium hexametaphosophate. These compounds act by causing the sequestration of the calcium and magnesium ions.
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17. Laundry Detergent Formulations
Phosphate builders increase the eutrophication of lakes. Some states have banned their use. Zeolites trap calcium and magnesium ions in a cage-like structure.
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18. Laundry Detergent Formulations
Brighteners are added to detergent formulations to make clothing appear bright and new.
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19. Laundry Detergent Formulations
Liquid laundry detergents have captured much of the market in recent years. Liquid laundry detergents can either be built formulations with sodium citrate, sodium carbonate, or zeolites, or they can be unbuilt formulations high in surfactants and have no builders.
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20. Dishwashing Detergents
Liquid dishwashing detergents, for handwashing, usually contain one or more surfactants, such as LAS or cocamido DEA [CH3(CH2)nCON(CH2CH2OH)2].
Dishwashing detergents for automatic dishwashers are usually strongly alkaline. They can contain sodium tripolyphosphate, sodium carbonate, sodium metasilicate, and a bleach, along with a small amount of surfactant. Sodium hydroxide may also be present.
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21. Fabric Softeners: Quaternary Ammonium Salts
Quaternary ammonium salts with two long alkyl chains are used as fabric softeners. They attach to clothing fibers, forming a layer one molecule thick, which gives the clothing a smooth flexible softness.
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22. Laundry Bleaches: Whiter Whites
Bleaches are oxidizing agents that react with colored stains on fabrics. The more common bleaches are chlorine bleaches containing sodium hypochlorite (NaOCl). Oxygen-releasing bleaches contain either sodium percarbonate (2 Na2CO3 . 3 H2O2) or sodium perborate (NaBO2 . H2O2). These bleaches liberate the oxidizing agent hydrogen peroxide in hot water.
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23. All-Purpose Cleaning Products
A number of all-purpose cleaning products are commonly found in the home. These include household ammonia solutions, baking soda, and common vinegar.
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24. Special-Purpose Cleaners
Toilet bowl cleaners are usually acidic materials to remove calcium carbonate deposits.
Scouring powders contain abrasive materials like silica (SiO2). They may also contain a surfactant and bleach.
Glass cleaners contain isopropyl alcohol, ammonia, and sometimes vinegar.
Drain cleaners usually contain sodium hydroxide to saponify grease. Some contain bits of aluminum that react with the NaOH to release hydrogen gas to agitate the clog. Many contain bleach to degrade hair.
Oven cleaners contain NaOH to cut the greasy material on oven walls.
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25. Organic Solvents in the Home
Organic solvents are available for removing paint, adhesives, waxes, and other materials. Most are volatile and flammable.
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Paints
Paints include lacquers, enamels, varnishes, oil-based coatings, and water-based finishes. They are composed of three basic ingredients: a pigment, binder, and solvent.
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Waxes
Waxes are esters of long-chained fatty acids and long-chained alcohols. Paraffin wax is a mixture of long-chained hydrocarbons. Waxes serve both plants and animals as protective coatings. Many natural waxes are being replaced by silicones.
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Cosmetics
The U.S. Food Drug and Cosmetic Act of 1938 defined cosmetics as “articles intended to be rubbed, poured, sprinkled, or sprayed on, introduced into, or otherwise applied to the human body or any part thereof, for cleansing, beautifying, promoting attractiveness, or altering the appearance…” The main difference between drugs and cosmetics is that drugs must be proven “safe and effective” before they can be marketed.
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Cosmetics
Skin Creams and Lotions
Cosmetics are applied to the dead cells of the corneal layer of the skin.
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Cosmetics
Skin Creams and Lotions
A lotion is an emulsion of oil droplets dispersed in water.
A cream is an emulsion of water droplets dispersed in oil.
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Cosmetics
Skin Creams and Lotions
The oily substance of the cream or lotion forms a protective film over the skin that retains moisture.
Emollients protect the skin by coating and softening it.
Moisturizers hold moisture to the skin.
Humectants, such as glycerol or lactic acid, actually attract water to the skin.
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Cosmetics
Sunscreen Lotions
Sunscreen lotions work by blocking short-wavelength (UV-B) radiation, but allowing the less harmful long-wavelength (UV-A) radiation to pass. Older formulations contained paraminobenzoic acid (PABA), which is water-soluble. Newer formulations contain octyl methoxycinnamate (OMC), which is insoluble in water. Skin protection factor (SPF) tells how long you can stay in the sun compared to no protection. I.e., an SPF of 15 means that you can stay in the sunlight 15 times longer than with no protection. Sunblocks contain opaque powders like zinc or titanium oxide that block all UV radiation.
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Cosmetics
Lipsticks and lip balm are similar to skin creams or lotions in make up and function. They contain oil and a wax and work by holding moisture against the skin.
Eye makeup is used to accentuate and decorate the eyes. They typically contain waxes, soaps, fats, oils, and pigments.
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Cosmetics
Deodorants and Antiperspirants
Deodorants contain perfume to mask body odor and a germicide to kill odor-causing bacteria.
Antiperspirants may contain perfumes and germicides, but also contain compounds such as aluminum chlorohydrate [Al2(OH)5Cl . 2 H2O], which are astringents that constrict the pores of sweat glands to prevent perspiration.
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Toothpaste
Toothpaste is perhaps the most important cosmetic product. Toothpastes are typically composed of a detergent and an abrasive. In addition, there are flavoring agents, coloring agents, sweeteners, and thickeners.
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36. Perfumes, Colognes, and Aftershaves
Perfumes may contain many ingredients. Their components are divided into three “notes”. Notes are categories of volatility. The first note is the most volatile fraction and the third or end note is the least volatile fraction. The end notes often have musky odors.
Colognes are perfumes that have been diluted with alcohol or alcohol/water mixtures.
Aftershave lotions are similar to colognes, but contain a higher percentage of alcohol. Some contain menthol or an emollient.
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Hair Chemistry
Shampoos contain a detergent such as sodium dodecyl sulfate. They can also contain coloring agents, fragrances, and proteins for repairing split ends.
Conditioners are mainly long-chained alcohols or quaternary ammonium salts that coat the surface of the hair and allow the strands to slide past each other.
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Hair Chemistry
Hair color is determined by two pigments, melanin (brownish-black) and phaeomelanin (red-brown). Hair color can be lightened by oxidizing with hydrogen peroxide or changed by dying.
Hair treatment like Grecian Formula® contains lead acetate [Pb(CH3COO)2]. The lead ions penetrate the hair shaft and react with the sulfur to form black lead sulfide.
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Hair Chemistry
Perms are accomplished by breaking the disulfide bonds in the proteins with reducing agents, such as thioglycolic acid. The hair is then curled on rollers and treated with hydrogen peroxide to reestablish new disulfide linkages.
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Hair Chemistry
Hair sprays are resins that form a sticky film to hold the hair in place. A mousse is simply a foam that contains such a resin.
Hair removers are called depilatories. Most contain a strongly basic soluble sulfur compound that attack the peptide bonds in the hair so that it can be washed off.
Hair restorers, such as Rogaine®, contain Minoxidil. Minoxidil was first used as a treatment for high blood pressure. It has the ability to grow fine hair when it is applied to any skin where hair follicles are located.
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41. The Well-Informed Consumer
Many companies spend a lot of money on advertising their products and the most expensive product is not always the best. It is worth the effort to be informed about the products that you buy and use.
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