Soaps&detergents Paper

Brown 1 Gabrielle Brown Ms. Hodsden English IV 20 October 2009 A world without cleanliness would be an unbearable one: from the reeking stench to the rampant disease, life would be miserable, if at all existent. Thanks to a bit of natural chemistry, people discovered soap long ago and since then have been developing new ways to alter and harness the power of this most critical cleansing agent. Since the time of soap’s discovery, humans have created specialized soaps, scented soaps, barred soaps, pigmented soaps, and even a new cleansing agent altogether: detergent. Soaps and detergents have been a part of human lifestyles for many centuries. They have an interesting way of operating, can be made in various ways, and are used for a large array of tasks and specialized work in today’s modern world. Soaps and detergents must undergo a series of basic steps in order to clean a substance: wetting the dirtied material, detaching the dirt particles from the material, and keeping the dirt particles in the water until they are rinsed away. When cleaning a material with soap or detergent, one must first begin by using water to make the substance wet. Within soaps and detergents are surfactants (“Detergent” 164). A surfactant, shorthand for ‘surface-active agent’, is a double-natured molecule where one part of it is soluble, or dissolvable, in water and another part of it is not. The salts of fatty acids are the surfactants in soaps (Ball), and synthetically made molecules that mimic the design of soap’s fatty acids make up the surfactants in detergents (Farhat 133). A surface-active agent is composed of a head and a long tail. The head end of the surfactant is charged negatively and reacts considerably with positively charged hydrogen in water molecules, thus making the end water-soluble. The tails of surfactants do not have an

Brown 2 affinity for water, but rather for oily hydrocarbon liquids and greases with chemical structures resembling their own, making the tail end of a surfactant water-insoluble. Surfactants are amphiphiles, or molecules with dual natures, and it is because of this property that surfactants are able to lower the surface tension of water. Electrical forces of attraction between molecules hold all liquids together. Surface tension is a net inward force of the surface molecules of a liquid that occurs because surface molecules only have molecules below them to attract to (Ball). By lowering water’s surface tension, surfactants allow for the material being cleaned to be penetrated by water more thoroughly. The next stage in the cleaning process of soaps and detergents is the stage where the dirt is removed, and surfactants play a key role yet again. The head ends of surfactants are hydrophilic, or attracted to water, whereas the tail ends are hydrophobic, or repelled by water; both of these phenomena are caused by electrical attractions between molecules. The hydrophobic tails of surfactants do not attract to water, but instead to the particles of dirt within the soiled material. The hydrophilic heads, meanwhile, attract to the water surrounding the soiled material, which then pulls the tail end, along with the dirt the tail has attracted, off of the material and into the water. Agitation aids in speeding up this process by fracturing the dirt into minute particles and by helping the hydrophilic parts of the surfactant molecules draw the dirt off of the material (“Detergent” 164). Once surfactants have removed the dirt, the material is one step away from being clean. The final stage in the cleansing process involves the surfactants creating a thin layer of molecules surrounding the dirt particles to separate them and to prevent them from immersing into the once-soiled material again. The dirt particles that are surrounded by surfactants are then suspended in the wash water until rinsed away (Detergent 164). By the simple process of wetting

Brown 3 a material, detaching dirt particles from it, and holding the particles in water until rinsed away, soaps and detergents make excellent cleaners and stain removers. Soaps can be made in a large array of fashions, but the same general process takes place whether one is making soap in a traditional fashion or in the industrialized manner. “A true soap is composed of a base and a fat,” says long-time recreational soap maker, Steven Mitchem. The “base” ingredient is alkaline moieties such as sodium hydroxide, potassium hydroxide, sodium carbonate, and triethanolamine ( Farhat 126). Found naturally in wood ashes, this alkaline element is more commonly called lye (Hobson 11). The “fat” ingredients of soap are triglycerides, triesters of fatty acids, which are obtained from tallow (animal fat) or plant oils such as coconut, palm, and kernel (Farhat 125). Soap is the salt of fatty acid (124) derived by using the base to break the bonds between acid and alcohol sections of esters in a chemical reaction known as saponification (LeMay 855). Saphonification works by hydrolysis, which is a reaction where water is added to a reactant and that reactant becomes decomposed (p 950). After saponification, the reactants hydrolyze into glycerin and sodium stearate, commonly known as soap, as seen in figure (A) (Farhat 126). Perfumes, pigments, and other ingredients are not critical to the creation of soap, but rather are additives that make the soap more appealing; accessory ingredients can improve the cleaning ability of the soap, make it a nicer color, add a desired aroma to it, or give the soap skin-softening characteristics (Hobson 9). Soap making style can be classified in two basic methods: the traditional style, and the industrial style. The traditional style of making soap is a very simple one: the maker heats the fat into a liquid, combines the lye with water, and then mixes the two while over heat and adds in any perfume or extraneous ingredients (Mitchem). In the industrial process of making soap, the process begins with the pre-heating of fats and the catalyst, a reaction rate increaser, and then

Brown 4 sending these materials to a machine called a hydrolyzer. As the name implies, the fat is hydrolyzed here by the addition of deaerated-demineralized water creating fatty acids and glycerin (Farhat 127). The fatty acids are flushed out of the top of the tank and are sent to a flash tank, where the water is removed. The fatty acids are then deaerated to prevent darkening by interactions with oxygen, and then distilled in a high-vacuum still. They are then sent to the bottom of the still and cooled down to room temperature in two parallel condensers (129). The fatty acids must then undergo a neutralization reaction, which is a chemical reaction between a base and an acid that terminates the distinguishing qualities of both substances. The products of neutralization reactions are water and a salt (LeMay 951); in this particular instance, the salt is soap. The fatty acids next go to a high-speed mixer neutralizer where they become neutralized by the addition of fifty-percent caustic soda. Caustic soda is evaporated soda lye in which the active ingredient is an alkaline (Hobson 11). At this stage in the manufacturing process, the substance is called neat soap (sixty to sixty-three-percent total fatty matter) and is sent to a blender to create an even neutralization. From here, the soap can be removed for conventional soap production or undergo further treatment by high pressures and temperatures, drying, air combination, and cooling. The soap is then cut into bars, cooled further, stamped, and wrapped, creating a final product of aerated bar soap (Farhat 129). Whether traditional or industrial, it is interesting to observe that the same chemical reactions that were discovered centuries ago still take place in order for soap to be made. The manufacturing of detergent varies greatly with that of soap. Detergents are most importantly comprised of water-soluble surfactants, surfactants that can easily dissolve in aqueous solvent. These water-soluble surfactants are composed synthetically by attaching a

Brown 5 hydrophilic group to a hydrophobic material. Another key factor of detergency is the balance in molecular weight between the hydrophilic portion and the hydrophobic portion (Farhat 133). The manufacturing of detergent begins with the making of detergent slurry, which contains liquid surfactants. These liquid surfactants are alkylbenzene sulfonates and are produced by sulfonating (Fathat 153), adding a sulfuric acid group (“Sulfation”), linear alkylates and then neutralizing with a caustic solution composed of sodium hydroxide. Next, the products of sulfuric acid and sulfonic acid are aged for fifteen to thirty minutes and then diluted with water. The mixture is then sent to the acid settler where gravity separates the two acids due to the mass difference between the heavier spent sulfuric acid and the lighter sulfonic acid. The linear alkyl sulfonates are then neutralized with a base such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, or alkanolamines. The resulting solution salts then move on to a spraydrying process: the detergent slurry is added into a machine called a crutcher along with other additives where the ingredients are mixed. The blend is then sent to a stirred storage container and continuously pumped into a spray dryer. At high-pressure levels, the slurry is sprayed onto a vertical drying tower, usually countercurrent in design. From the drying towers, the newly made detergent granules are put into a mixer where more additives, such as perfume, are combined as well. Finally, the detergent is packaged and put on the market (Farhat 153). This process makes the detergents people use everyday effective and readily available. The widespread use of soaps and detergents has only grown since the ages of their discoveries, as they are both used for a variety of tasks in today’s modern and rapidly changing world. The cleansing abilities of soaps and detergents are used in an impressive array of fields and specialized work, as well as for everyday hygiene and maintenance. Presently, detergent usage has dominated that of soap; in fact, most of the commercial hand, facial, and body ‘soaps’,

Brown 6 toothpastes, shaving creams, etc. are actually detergents (Mitchem). However, soap still remains a large part of society due to recreational soap makers who enjoy making their own recipes and formulas, and also through soap makers who venture to introduce their products into the detergent-ruled market. Certain detergents are used to help clean up oil spills and leaks that would otherwise take nature months to recover from. The popular dish detergent “Dawn” is used to clean off animals, such as reptiles, fish, mammals, amphibians, and birds, that would suffer adverse side effects and eventually die from being coated in the grease. Cleaning birds that have been covered in grease is a daunting task, but Alice B. Berkner of the International Bird Rescue Research Center exclaimed that when washing the birds with “Dawn” detergent, the “oil seemed to fall off the feathers!” When cleaning animals with the detergent, rinsing was made easier and skin irritation did not occur. The detergent is also convenient for the fact that it is inexpensive and easily obtained (Berkner). Thanks to the employment of detergent, the mortality rate of birds and other wildlife after oil pollution has dramatically decreased. Soaps and detergents are also used in the field of aromatherapy. Aromatherapy is the study of scent where the skilled and controlled use of essential oils is utilized for both physical and emotional heath and wellness. Essential oils are the “essence” of a particular plant form from which they are derived. They are tiny droplets contained in glands, glandular hairs, sacs, or veins of various plant parts (Cooksley). Aromatherapists utilize the ability of soaps and detergents to carry essential oils, as well as herbs and parts of plants. Soap and detergent can house desired perfumes that the therapists use to treat their patients with.

Brown 7 Today, soaps and detergents can be found in all manner of public and private residences, including schools, churches, offices, restaurants, and homes and have become a part of many peoples’ day-to-day lives. People have made many noteworthy advances in the science behind soaps and detergents since each of their discoveries. These advances would not have been made possible without first possessing an understanding of how soaps and detergents clean, how soaps and detergents are made, or of the applications of soaps and detergents in the surrounding world. Soaps have been detrimental to the survival of humans for centuries, and now, along with detergents, they will continue to play their roles (and probably develop a couple of new ones) in human life for generations to come.

Brown 8 Works Cited Ball, Philip. The Self-Made Tapestry: Pattern Formulation In Nature. NY: Oxford University Press, 1999. questiaschool.com, 18 October 2009. Berkner, Alice B. “It Was Pretty “Dark” Before “Dawn.” International Bird Rescue Research Center. 2009. 7 November 2009. http://www.ibrrc.org/index.html Cooksley, Valerie Gennari. Aromatherapy: A Lifetime Guide to Healing With Essential Oils. Paramus, NJ: Prentice Hall, 1996. “Detergent and Soap.” World Book Encyclopedia. Chicago: World Book, Inc., 2006. Farhat Ali, El Ali, Speight. Handbook of Industrial Chemistry, Organic Chemicals. New York, NY: The McGraw-Hill Companies Inc., 2005. Hobson, Phyllis. Making Soaps & Candles. Pownal, VT: Storey Communications, Inc., 1973. LeMay, Robblee, Beall, Brower. Chemistry: Connections to Our Changing World. Upper Saddle River, NJ: Prentice Hall, 2000. Mitchem, Steven. Personal Interview. 29 September 2009. “Sulfation.” Dictionary.com: An Ask.com Service. 2009. 30 September 2009. http://www.dictionary.reference.com/browse/sulfation

Brown 9 Figure (A): 3NaOH + C17 H35 COO3 C3 H5  3C17 H35 COONa + C3 H5 (OH)3 Sodium Hydroxide

Glyceryl Stearate

Sodium Stearate

Glycerin