Silicates:

Jump to: What are Silicates?

Historical Uses Implications

How Silicates are Used in Cars? Durable Concretes from Using Silicates Silicate Technology

Silicates in Computers Silicates in Clocks

Silicates in Cosmetics and Hygiene Appendix References

What Are Silicates?

Although silicates are ever present in our lives, the knowledge of the minerals are largely unnoticed by the general public. Silicates make up more than 87% of the earth’s crust, unsurprisingly making their way into the lives of millions of people as well as numerous scientific practices. [4] The most basic definition of a silicate is a compound containing [SiO4]4- anions, however there are numerous branches of silicates that include oxygen atoms replaced by fluorine atoms to make hexafluorosilicates or other exceptions. The category of silicates itself includes over 500 different minerals, making them the most widely used mineral type on the planet. Thusly, raw materials are often times referred to as silicates as they are the building blocks of society. [1] Silicates are composed of both Silicon (Si) and Oxygen (O), making them the most abundant elements in the earth’s crust. These two elements are reactive as oxygen readily wants electrons and silicon can provide them. Silicon is structured in a way where it wants to be “reduced” or lose electrons. These two elements come together to share electrons to form a covalent bond, which is a considerably strong bond between atoms. The most common structure is 1 silicon with 4 oxygen atoms (figure 1) bonded around it in a ‘tetrahedral’ structure. However, other structures exist, contributing to the large variety of uses for the umbrella of silicates.

Figure 1: Anion silicon compound structure (silicate) [4]

Silicates have unique abilities to conduct

electricity at extremely small sizes, which make them very useful in microchips. In turn, microchips are found in every computer, gaming device, and cell phone. Their compact structural unit allows them to create durable and hard crystals, perfect for making powerful technology at small sizes. Their strong compact structure has use in creating long-lasting abrasion and chemical resistant buildings. Many silicates are completely resistant to dissolving in water, making them very useful in construction. Sodium silicates are soluble in water; however, they are used extensively in the creation

of concrete. Historical Uses

The earliest uses of silicates extend back to 5000 B.C. where the Egyptians industrialized pottery and ceramics. Silicates were profoundly used in making durable primitive tools, smooth containers, and even strong roofs to survive storms and keep warm.

Glass making arrived in the third century B.C. Today, glass making has

been largely industrialized in numerous fashions. However, all methods of glass making use silica as a major component which is heated up to over 1700° Celsius. Interestingly enough, the types of silicates used influence the type of glass created as an end product. For example, using quartz in

combination with other minerals creates fused quartz glass, commonly used in telescopes, while silica sand and limestone create glass fibers, largely used in thermal and electrical insulation. Mixing sand silicates with aluminum makes scratch resistant glass on iPhones and other cellphones. Manufactures around the world constantly attempt to find a more resistant and cleaner glass that will see commercial use in the realm of technology.

In the twentieth century, strides in actually

understanding structures and uses of silicates were seen.

Figure 3: Egyptian Pottery [9]

Figure 1: Dioptase, a copper derive silicate [8]

Figure 4: Pouring Cement [10]

William L. Bragg published a paper in 1930 on the actual structure of silicates shortly after Felix Machatschki developed the concept of atomic structures of silicates. In 1936, Harry Berman made a large amount of progress in actually classifying them during his time at Harvard University. Their work in classification and structure analysis spring-boarded our applications today. It is incredible to think this work was done less than 90 years ago, yet the advancements in technology has increased so much. [6]

Applications of silicates are constantly being created today, such as cement, the largest

growing cement being ‘Portland cement’ that is composed of numerous silicates, namely sodium derived silicates [3]. Cement is visible everywhere, but it’s interesting to think the science behind it is ignored. To put it into perspective, China and USA put down over 10 gigatons of cement in the last 3 years, which can roughly make a parking lot the size of 1.2x1010 meters squared, or a slightly larger area than Hawaii… [2] Implications

In the near future, dental cements used for the re-mineralization of teeth may be used. Cavities and poor teeth health may be overcome with the research of Timothy Watson and calcium silicate cements. Using this type of silicate treatment, new restorative materials may be placed into teeth, providing support for decaying teeth and perhaps repair teeth that have been crippled through wear and tear. [7]

For those anxious of starting construction on mars in

upcoming years, there is no need to worry as there are silicates present on mars. Because of the properties of silicates and its oxygen component, many argue that life may be sustainable on mars! Silicates may even be a viable source for colonizing Martian soil in the future. According to an x-ray diffraction of mars, the mineralogy of mars is largely composed of silicates. With the right tools, theories of creating oxygen reactive species have been established by using ‘simulated wind-driven saltation’ (basically erosion with wind) [5]. This leads to the abrasion of silicates and through a series of chemical reactions, reactive oxygen species are created. Unfortunately, the oxygen produced through this method does decrease the survival of certain micro-organism on mars itself. However, further experimentation beyond laboratory simulation is required and perhaps colonizing mars can be done through the use of silicates that can give off oxygen!

Figure 5: Surface of Mars [11]

How Silicates are Used in Cars Cars are a luxury that people can drive around to different places for work, school, or

social activities. However, some people undermine the responsibilities of owning a car. For example, many people do not know what coolant is and how it helps a car maintain normal functionality. Coolant (also known as antifreeze) is a mixture of solutions that helps keep engines from freezing, overheating, and corroding. Coolant basically allows an engine to sustain good health by balancing the temperature changes and provides protection from deteriorating metals [12]. Antifreeze is mostly made up of water and ethylene glycol, but there are many other ingredients that are vital to the function of coolant. Even if it is only a small fraction of the solution, silicates play a major role in stabilizing cars.

Silicates are the main components of the inhibiter system in engines where they form a blanket of protection that insulate the metals. As an inorganic oxide, silicates provide protection from corrosion by interacting at metallic corrosion sites where the metals usually react with different chemicals. Because of silicates, coolant degrades due to rapid inhibitor depletion where the silicates’ protective layer is worn out. Coolant needs to be changed or replenished so that the silicate layer protecting the engine is restored for optimal use. As a sealing agent, silicates also help prevent leakage when used in coolant. Sodium silicate is known as liquid glass

where it is made by combining sodium carbonate and silicon dioxide which results in a white powder that seems to have the same usage and qualities as salts [13]. When the powder is dissolved and heated to over 210 degrees Fahrenheit, the sodium silicate loses its water molecules and liquefies into a fragile, thin layer of glass. Though it may by fragile, the glass layer seals leaks in the engine and will not melt at anything under 1500 degrees Fahrenheit, making the silicate a very powerful and effective sealing substance. In an engine, the glass layer of sodium silicate in coolant will stick to any hot and sharp edges where there seems to be a crack in any part of the engine where antifreeze is circulated. How the liquid solidifies in the crack is simple. The hot air around the crack dries the liquid glass into a crystalline form. The silicate will build up over time where a high concentration of the glass layer is present, and the crack will eventually be sealed.

Sealing with glass can be concerning because glass is brittle, so the silicate has some amounts of metal ions to strengthen the substance to make the crack repair more effective. There may be some downsides to having silicates in the antifreeze, such as the brittleness of the liquid glass that forms and needing to constantly replenish the coolant. But overall, silicates are favorably used to help keep a car’s function in stability.

Figure 6: Green coolant is added to the radiator [16].

Durable Concrete from Using Silicates

Concrete has many different properties that make up the hard and strong structure used in buildings and streets. Concrete is made up of water, rock, and Portland cement. Silicates make up around 75 percent of the chemical composition of Portland cement in which the silicates provide a big contribution to the durability of concrete.

The silicates function to provide the strength of concrete where the silicates chemically react with different substances to change the composition of cement. More specifically, water needs to be added to the silicates, such as tricalcium silicate, to undergo hydration to release

calcium ions, hydroxide ions, and large amounts of heat [14]. Then calcium silicate hydrate crystals begin to form which grows thicker and thicker, making cement less malleable.

The production of hydrated silicates become slower as almost all of the unhydrated silicates undergo chemical reactions to create the hydrates. The strength of the concrete is dependent on the hydration reaction. Since water helps determine the strength and speed of the reactions, people usually use much more water in the

mixture than needed. As less water is used, the faster and stronger the concrete will become. The speed at which concrete hardens won’t allow much time for workers to make use of it. This occurs because it is hardening too fast for people to shape, form, or place the concrete to where it needs to be. Thus, more water is used to give the concrete sufficient workability where workers will have a longer period to make sure the concrete is appropriately placed.

Microsilica, also known as silica fume, is another

type of silicate that adds to the concrete’s durability. It

provides a better distribution and greater volume of hydration products by decreasing the average size of pores in the cement paste [15]. Silica fume particles are so small that they evenly disperse among the cement to create greater bond strength as well as increase electrical resistivity, making microsilica a good protective reinforcement for buildings and streets.

Figure 7: Workers placing down concrete [17].

Figure 8: The Templin Residence Hall from the University of Kansas [18].

Figure 9: A pure silicon crystal, called an ingot. [20]

People need to have the right ratio of silicate comprised cement to water to have a strong and effective structure that provides stability to anything that is being built, such as streets or buildings. It may take a great amount of time for all the silicate hydrates to form, which could take up to years because the hydration reactions become slower as the hydrates become thicker, showing that the relative strength of the concrete also has a time factor. This would explain why buildings take so long to be constructed because workers need to wait for the wet concrete to dry which could take months before people can continue on with the productions. However, this time waited creates a very durable substance that is essential for long lasting structures.

Silicate Technology

An often-overlooked aspect of silicates is their uses in technology. Silicon and silicates

can be used as semiconductors or insulators, a major part of computer chips and transistors. Quartz, a common silicate mineral, has piezoelectric properties which can lead to interesting applications. Piezoelectricity means that a substance will responds to mechanical stress with an electric potential. This is used in a variety of technologies, mostly to keep track of time.

Silicates in Computers

Silicon is a major component of any modern computer chip and there are a few reasons for its ubiquity in the computer world. The qualifying reason, or the reason that silicon can be used at all is due to the fact that it is a semiconductor. Semiconductors are materials that can both conduct electricity like a metal or insulate like rubber. This allows the transistors in a computer need to be able to switch on and off rapidly at room temperature. [19] There are other materials that are semiconductors and some are even better than silicon. For example, both germanium and gallium arsenide have better electronic material properties but silicon can withstand higher temperatures and is very cheap to produce. [19]

One other reason is the abundance of silicon on earth. Silicon is the eighth most abundant element on Earth [19] and, as mentioned in an earlier section, silicate minerals make up around 90% of the Earth’s crust. As it exists in nature, silicon is usually bonded to other elements (like oxygen to make silicates) but, luckily, scientists have developed methods to grow silicon crystals dependable ways to isolate silicon. [20] These crystals are

called ingots and they can be cut into thin wafers, which are then heavily processed to make computer dies. Currently the ingots are made in 300mm diameter cylinders but soon could be made into 450mm diameter cylinders. [20] This greatly reduces the cost of production for the large billion-dollar computer companies, passing on the benefit to you and your wallet.

Before more is discussed about the use of silicon in computers, the structure and function of transistors needs to be explained. To begin, silicon is purified and made into the previously described crystalline structure with very few impurities. [21] Pure silicon in its crystalline structure cannot conduct electricity so it undergoes what is called “doping”. This increases the conductivity of whatever material was doped. The agent that is introduced into the semiconductor is called a dopant. For silicon, both boron and phosphorus are used as dopants and they create two different types of conductivity. Phosphorus has one more valence electron than silicon so when it is added, the extra electron is free to move about the entire structure creating a negative charge and n-conductivity. Boron is just the opposite with one less electron and it creates a hole which sort of acts as an anti-electron that floats through the entire structure. The boron impurities will create a p-conductive material. The p-conductive and n-conductive materials are then layered in a specific pattern to create a transistor. [21]

A very common type of transistor is the MOSFET (Metal Oxide Semiconductor Field Effect Transistor) transistor that is used for a variety of electrical devices. [22] The basic structure of a MOSFET transistor is shown to the right. The n+ regions are the n-conductive regions made of the phosphorus doped silicon. The p region underneath is composed of the boron doped silicon. Above both regions there is a layer of silicon oxide (labeled Oxide) that acts as an insulator (This is another reason silicon is heavily used as a transistor as the creation of the insulating layer is very cheap and easy [19]). Applied on top of the insulating layer is a layer of some conductive material. [21] The transistor has 4 connections but the body is often combined with the source. [22] How MOSFET works is that some voltage is applied to the gate. Let’s say for this example we are using the transistor that is pictured so a positive charge would be applied. The charge then attracts electrons to collect underneath the silicon oxide layer, creating a channel that connects the two n+ regions. Now the source and drain terminals are connected and the electrical circuit is closed. The transistor can be switched on and off simply by applying a charge through the gate connection. [21]

Silicates in Clocks Quartz is perhaps the most common mineral on the Earth and is the low temperature stable version of silicon dioxide. The structure of quartz can slightly vary but the most interesting and relevant property of quartz is its piezoelectricity. Piezoelectricity as explained earlier is the ability to convert mechanical stress into electrical currents. This is due to the distribution of charges in a piezoelectrical crystal. The negative and positive charges are separated but symmetrical, making the overall crystal neutral. The force that is applied disrupts the symmetry of the crystal and produces a current. The reverse of piezoelectricity can happen as well, meaning that if a current is passed through quartz then it will output some force. This property allows the quartz crystal to receive energy and alter it to produce oscillations. [23]

Figure 10: A basic MOSFET transistor [22]

Figure 11: Urban Decay’s Naked Heat Eyeshadow Pallet that is

made with Calcium Sodium Borosilicate and Silica [30]

Figure 12: Urban Decay All-Nighter Foundation that is made with

Magnesium Sulfate [31]

This is very useful in clocks because the oscillations (vibrations) of quartz can be tuned to a specific frequency. In quartz watches, this is 32768 times a second. The quartz is connected to a circuit that counts the frequency which can then be translated to seconds, minutes, and hours. [24]

Silicates are a very versatile group of molecules that uses aren’t simply limited to buildings or makeup. Silicon is heavily used as the primary semiconductor for many companies. As engineers reach silicon’s physical limitations a new semiconductor may appear to replace it but currently that is not likely because of its abundance and cheap cost to produce. Quartz provides another interesting side to silicates because of it piezoelectricity. The applications are not simply limited to clocks either as many early technologies also utilized quartz.

Silicates in Cosmetics and Hygiene Have you ever used makeup, soap, or detergent? In a 2011 study, conducted by the

Renfrew Center Foundation, it was found that one fourth of the woman surveyed in the US started wearing makeup before the age of 13 [25]. The annual revenue of the detergent and soap industry was about 27 billion dollars as of 2010 [26]. The cosmetic and hygiene industries are widely known and are increasingly popular. Why are these facts relevant to silicates? Silicates are main components for many brands in these industries including Bare Minerals, Urban Decay and Tom’s. Sodium Silicate, sodium Metasilicate and Potassium Silicate are used in many skin care products, hair coloring products, shaving creams, eye makeup and oral hygiene products [27,28]. Silicates are prevalent throughout the cosmetic and detergent industries as they are used as buffering agents, absorbents, builders, abrasive agents and much more [29].

If you use makeup, you probably know the brand Urban Decay; you may even own a couple Naked Eyeshadow pallets. Some silicate based Urban Decay products you may be familiar with include All-Nighter Foundation and concealer and the Naked Heat Pallet (see figure 11 and figure 12) [30, 31]. Other makeup companies also use silicates including Bare Minerals in their Sheer Cover Mineral foundation [32]. Why are silicates used in makeup? They have many important properties such as buffering agents, absorbents, anticaking agents, opacifying agents and bulking agents [29]. Buffering agents

are used in cosmetics to maintain the pH of the product. PH determines how acidic or basic a solution is through a 14-point scale where 1 is extremely acidic and 14 is extremely basic. If the pH of skin products is off, it can disrupt the external layer of skin cells causing dehydration, and flaking. It can also leave your skin defenseless to the environment; an increase in pH over 6.5 can

Figure 14: Builders bonding to metal ions (like Ca+) and precipitating out of the solution [43]

Figure 13: Surfactants solution surounding the oil particle and

removing it from the fabric surface [41]

damage our skins natural defense barrier, and this leads to an increased risk of bacterial infections [33]. By controlling the pH so that the products are in a safe range for skin use, silicate help prevent dehydration in skin care products and decreases bacterial infections. Aluminum iron silicates act as absorbents in cosmetic products by increasing a product’s ability to absorb liquids. When used as an anticaking agent, it prevents the clumping of makeup products such as foundations weather as powder or liquid form. Ever have foundation that’s too translucent? Adding silicates can remedy this problem. Silicates act as opacifying agents in makeup. Opacifying agents reduce the transparency of makeup products such as foundation so they are more efficient in covering blemishes [34]. Silicates such as Alumina Magnesium Metasilicate also act as bulking agents which are used to increase the volume of a product by diluting the original product but not changing the original properties [35]. Silicates are used widely through the cosmetic industry and provide many different beneficial aspects.

Want white teeth? Try buying Crest or Tom’s toothpaste. Both brands use silicates which act as abrasive agents [36, 37, 38]. Abrasive agents help whiten teeth because they are scratchy materials that help scrub teeth effectively removing stains as well as food and bacteria. Silicates also act as oral care agents because they reduce oral odors [38]. Hydrated silica creates a gel consistency in toothpaste and acts as a mild abrasive at the same time [39]. If you wash your clothes, chances are you use a detergent that contains silicates. Silicates act as builders in detergents. Builders’ main functions are to enhance the cleansing abilities of the surfactants. Surfactants are the main component of detergent and responsible for the removal of most oils and dirt. Surfactants break down the boundary between water and the dirt and oil particles (see figure 13) [40]. Builders prevent the loss of surfactants by bonding with calcium and magnesium ions (see figure 14). This prevents the formation of scum which is a white precipitate that forms from the reaction between carboxylic acids and the two metal ions stated before [41]. Because of this, builders are used as water softeners [42]. Silicates are considered precipitate builders because they help soften water by forming precipitates with metal ions in the solution [41]. Precipitates are the solids that form when two precipitants react

in a

solution. In addition to extracting metal ions from a solution, silicates have anti-redisposition properties, which means they prevent the resettling of dirt and

oils that are broken down by suspending them above the fabric [42]. Because of this, the particles and precipitates can be easily washed away. Aluminum silicate acts as an anti-caking agent for powder detergent, along with the foundations, and this keeps the powder dry, smooth and clump-free [41]. Some silicates also act as emulsifiers which means they can disperse greasy and oily particles [44]. This allows surfactants to surround the oil and dirt particles more easily. Chemistry relates to everyday life in many ways and very few people understand how silicates impact their lives. Silicates are the most abundant minerals on earth; their two components, oxygen and silicon, are the number one and number two most abundant elements in the earth’s crust [45]. Few people understand how silicates are used in everyday life on the molecular level because chemistry is not a topic that frequently comes up in casual conversation. Elements and atoms make up everything and understanding chemistry can help one understand what is happening in the world around them. Why does ice float? Why do onions make people cry? These questions can be answered through chemistry. Knowing why silicates are used and what they do can help one know which toothpaste brand they should to buy, and which makeup product will be less translucent. By knowing how silicates act on a molecular level, one can purchase the detergent, foundation and skin care products that fit their needs.

Appendix pH - The molar concentration of hydrogen atoms in a solution on a 14-point scale where one is acidic, seven is neutral, and 14 is basic. The pH of a solution can be calculated using the logarithmic equation pH = -log10[H+] [21].

References [1] Silicates http://asdn.net/asdn/chemistry/silicates.php (accessed Nov 19, 2017).

[2] Allain, R. How Much Cement Has China Used? https://www.wired.com/2014/06/how-much-cement-has-china-used/ (accessed Nov 15, 2017).

[3] Portland cement https://en.wikipedia.org/wiki/Portland_cement (accessed Nov 15, 2017). [4] Silicate https://en.wikipedia.org/wiki/Silicate (accessed Nov 15, 2017). [5] Bak, E. N.; Larsen, M. G.; Moeller, R.; Nissen, S. B.; Jensen, L. R.; Nørnberg, P.; Jensen, S. J. K.; Finster, K. Silicates Eroded under Simulated Martian Conditions Effectively Kill Bacteria-A Challenge for Life on Mars https://www.frontiersin.org/articles/10.3389/fmicb.2017.01709/full#B4 (accessed Nov 15, 2017). [6] Timeline of the discovery and classification of minerals https://en.wikipedia.org/wiki/Timeline_of_the_discovery_and_classification_of_mineral (accessed Nov 15, 2017).

[7] Watson, T. F.; Atmeh, A. R.; Sajini, S.; Cook, R. J.; Festy, F. Dental Materials 2014, 30 (1), 50–61.

[8] Alden, A. Which Rocks and Minerals Contain Silicate? https://www.thoughtco.com/what-are-silicate-minerals-4123211?utm_source=pinterest_ip&utm_medium=sm&utm_campaign=shareurlbuttons (accessed Nov 15, 2017). [9] Hood, R. Egyptian Pottery https://www.veniceclayartists.com/egyptian-pottery/ (accessed Nov 15, 2017). [10] Nayar, P. B. D. Global Concrete and Cement Market 2017 by Key Players: CRH, Votorantim, US Concrete, Cemex, Cimpor, Holcim, Buzzi Unicem, Italcementi and Lafarge http://incrediblenews24.com/20170919/global-concrete-and-cement-market (accessed Nov 15, 2017). [11] Composition of Mars https://en.wikipedia.org/wiki/Composition_of_Mars (accessed Nov 15, 2017) [12] Fritz, P. (2006, January 1) Engine Coolant Basics. Machinery Lubrication. http://www.machinerylubrication.com/Read/841/coolant-fundamentals

[13] Rowe, R. Sodium Silicate for an Engine. It Still Runs | Your Ultimate Older Auto Resource. https://itstillruns.com/sodium-silicate-engine-6376297.html [14] Scientific Principles. Concrete: Scientific Principles. http://matse1.matse.illinois.edu/concrete/prin.html [15] (1985, April 1) How Microsilica Improves Concrete. concreteconstruction.net. http://www.concreteconstruction.net/how-to/materials/how-microsilica-improves-concrete_o [16] http://mycarneedsthis.com/wp-content/uploads/2016/04/Engine_coolant.jpg [17] http://www.environmental-watch.com/wp-content/uploads/2014/09/cement.jpg [18] http://worldonline.media.clients.ellingtoncms.com/img/croppedphotos/2017/06/12/lewis_ge nder_inclusive-lead_t640.jpg?a6ea3ebd4438a44b86d2e9c39ecf7613005fe067 [19] (2014, June 11) Why only silicon chip is used in computers? Does it have any special property? UCSB Science Line. http://scienceline.ucsb.edu/getkey.php?key=4527 [20] Comment, G. T. (2015, June 22) What is silicon, and why are computer chips made from it? ExtremeTech. ZiffDavis. https://www.extremetech.com/extreme/208501-what-is-silicon-and-why-are-computer-chips-made-from-it [21] Agrawal, T. (2017, November 8) What is the MOSFET: Basics, Working Principle and Applications. ElProCus - Electronic Projects for Engineering Students. ElProCus. https://www.elprocus.com/mosfet-as-a-switch-circuit-diagram-free-circuits/ [22] hadleytugrazat. (2011, November 25). YouTube. YouTube. https://www.youtube.com/watch?v=jh2z-g7GJxE [23] Lang, C. (2004, January 14) Using Quartz Crystals in Digital Technology, Healing and Meditation. Satya Center. https://www.satyacenter.com/library/crystals/using-quartz-crystals [24] Woodford, C. (2017, May 17) How quartz watches and clocks work. Explain that Stuff. http://www.explainthatstuff.com/quartzclockwatch.html [25] NEW SURVEY RESULTS INDICATE THERE'S MORE TO MAKEUP USE THAN MEETS THE EYE. The Renfrewcenter Center Foundation for Eating Disorders. The Renfrew Center Foundation. http://renfrewcenter.com/sites/default/files/press_release_pdfs/Barefaced%20and%20Beautiful%20Release%20-%20FINAL.pdf

[26] (2010, November 2) Research and Markets: US Soap and Detergent Manufacturing Report: Top 50 Companies Generate about 90% of the $27 Billion in Annual Revenue. Business Wire. Business Wire, Inc. http://www.businesswire.com/news/home/20101102006035/en/Research-Markets-Soap-Detergent-Manufacturing-Report-Top [27] Sodium Silicate. Honest reviews of anti-aging skin care and beauty products. Truth in Aging. https://www.truthinaging.com/ingredients/sodium-silicate [28] Sodium Silicate. Sodium Silicate | Cosmetics Info. Cosmeticsinfo.org. http://www.cosmeticsinfo.org/ingredient/sodium-silicate [29] Silica. Silica | Cosmetics Info. Cosmeticsinfo.org. http://www.cosmeticsinfo.org/ingredient/silica [30] Urban Decay Naked Heat Eyeshadow Palette. ULTA Beauty. Ulta Beauty, Inc. http://www.ulta.com/naked-heat-palette?productId=xlsImpprod16251002 [31] Urban Decay All Nighter Liquid Foundation. Urban Decay. Urban Decay Cosmetics. https://www.urbandecay.com/all-nighter-liquid-foundation-by-urban-decay/ud778.html [32] (2007, June 22) INGREDIENTS LIST FOR POPULAR MINERAL MAKEUP FOUNDATIONS. eBay. eBay Inc. http://www.ebay.com/gds/INGREDIENTS-LIST-FOR-POPULAR-MINERAL-MAKEUP-FOUNDATIONS-/10000000001833019/g.html [33] Raincloud, J. (2017, May 1) pH Balance and Skin Care. Jenni Raincloud. Mediavine Publisher Network. http://jenniraincloud.com/ph-balance-and-skin-care/ [34] Glossary Terms beginning with O. Glossary Terms beginning with O | Cosmetics Info. Cosmeticsinfo.org. http://www.cosmeticsinfo.org/glossary/letter_o#Opacifying_Agent [35] ALUMINA MAGNESIUM METASILICATE. ALUMINA MAGNESIUM METASILICATE || Skin Deep® Cosmetics Database | EWG. EWG's Skin Deep. https://www.ewg.org/skindeep/ingredient/716541/ALUMINA_MAGNESIUM_METASILICATE/#.WhCYHrpFxfE [36] (2017, October 2) Crest Crest 3D White Whitening Therapy Enamel Care Fluoride Toothpaste, .85 Ounce - SmartLabel™. smartlabel.pg.com. Crest. http://smartlabel.pg.com/00037000737353.html#ingredients

[37] Sua. (2016, May 10) Fluoride-Free Rapid Relief Sensitive Toothpaste Toothpaste. Fluoride-Free Rapid Relief Sensitive Toothpaste. Tom's of Maine. http://www.tomsofmaine.com/product-details/rapid-relief-sensitive-toothpaste\ [38] Weighing Your Toothpaste Options. WebMD. WebMD. https://www.webmd.com/oral-health/guide/weighing-your-toothpaste-options#1 [39] Tom's of Maine. Hydrated Silica | Tom's of Maine. Tom's of Maine. http://www.tomsofmaine.com/ingredients/overlay/hydrated-silica [40] (2014) General Cleaners. Essential Industries - Manufacturer - Janitorial Maintenance Systems and Chemicals. Essential Industries, Inc. https://www.essind.com/general-cleaners/the-chemistry-of-cleaning/ [41] Marek Lichtarowicz. 2013. Surfactants. (March 2013). Retrieved November 18, 2017 from http://essentialchemicalindustry.org/materials-and-applications/surfactants.html [42] Inorganic Compounds of Detergents, Builders and Other Additives. Detergent Chemistry: Builders & Additives. HA Campbell. http://www.chemistry.co.nz/deterg_inorganic.htm#silicate [43] Rp, C. (1970, January 1) Chemistry in Surfactants, Home & Personal Care Products, Oleochemicals & Edible oil. LAUNDRY DETERGENTS FORMULATION. Bloggar. http://surfactantschemistry.blogspot.com/2013/07/laundry-detergents-formulation.html [44] (2017) Clean Living. Soaps & Detergents: Surfacants & Builders | Clean Living | American Cleaning Institute. American Cleaning Industry. http://www.cleaninginstitute.org/clean_living/soaps__detergents_products__ingredients_2.aspx [45] Nave, C. R. (2009) Silicates. Silicates. Georgia State University. http://hyperphysics.phy-astr.gsu.edu/hbase/Geophys/silicate.html