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You might have noticed stearic acid as an ingredient in the lotions, creams and soaps. Have you ever wondered, what is stearic acid and why is it used in the loations, creams and soaps? Stearic acid is a long chain saturated fatty acid which is used to stabilize the formulation and give smooth satiny texture to these products. In this article, we will study about stearic acid and properties, structure and uses of Stearic Acid.
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Keyterms: Soaps, Creams, Lotions, Carbon, Alkane, Octadecanoic acid, Stereophonic acid, Lipid, Insulators, Stearic acid, Fatty acid
Also Read: List of Strong Acids
What is Stearic acid?
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- Stearic acid is a saturated fatty acid with a long chain of carbon atoms.
- It is obtained from an octadecane (a straight-chain alkane carrying 18 carbon atoms).
- It is a white solid with a slightly pungent and greasy odour.
- The chemical formula of stearic acid is C18H36O2.
- Stearic Acid is also known as Octadecanoic acid and Stereophonic acid.
- It can be found in a variety of plant and animal lipids.
- It is mostly found in shea butter and cocoa butter as a component.
- It can float on water.
- It also acts as a plant metabolite, an algal metabolite, a Daphnia Magna metabolite, and a human metabolite all in one.
Read More: Dilution Formula
Properties of Stearic Acid
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| Chemical Formula of Stearic acid | C18H36O2 |
| Molar Mass of Stearic acid | 284.484 g·mol-1 |
| The density of Stearic acid | 0.9408 g/cm3, at 20°C 0.847 g/cm3, at 70 °C |
| The melting point of Stearic acid | 69.3 °C in 156.7 °F; 342.4 K |
| The boiling point of Stearic acid | Decomposes at 361 °C in 682 °F; 634 K 232 °C In 450 °F; 505 K at 15 mmHg |
| Thermal Conductivity | 0.173 W/m·K (70 °C) |
| Refractive index (nD) | 1.4299 (80 °C) |
Structure of Stearic acid
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Stearic acid has a crystal-like structure.
Chemically, it can be represented as:
Uses of Stearic Acid
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- Stearic acid has a bifunctional nature, the polar head group can be linked with metal activities while the nonpolar chain is soluble in organic solvents.
- Stearic acid is used as a surfactant and softening agent in a variety of applications.
- It is used as a culinary ingredient
- Stearic acid is used in the production of cleansers.
- Stearic acid is used for the pearly effect in soaps, cosmetics, and detergents.
- It is widely used in chewing gums.
- Candles are made from fatty stearic acid.
- It is widely used in the production of insulators.
- As an antioxidant coating for aluminium and iron powder to prevent oxidation.
Production of Stearic acid
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- The saponification of triglycerides in the presence of hot water at a temperature of around 100°C produces stearic acid. The resulting combination is distilled.
- Commercial stearic acid is usually a combination of stearic and palmitic acids.
- Purified stearic acid fats and oils are more productive in animal fat, which may be up to 30%, while it is generally less than 5% in vegetable fat.
- Stearic acid is made from carbohydrates with the help of the fatty acid synthesis machinery. In this, acetyl-CoA contributes to the formation of two-carbon building blocks.
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Adverse Impacts of Stearic Acid
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- When stearic acid and magnesium combine, magnesium stearate is produced, which is toxic and can cause a variety of adverse effects.
- This chemical molecule is also flammable and heats up spontaneously.
- Stearic acid is non-toxic but it can cause irritation in the respiratory system and skin.
Things to Remember
- Stearic acid is a saturated fatty acid with a long chain of carbon atoms which is obtained from an octadecane.
- The chemical formula of stearic acid is C18H36O2.
- It is also known as Octadecanoic acid and Stereophonic acid.
- It has a slightly pungent and greasy odour.
- Stearic acid has a crystal-like structure.
- Stearic acid is used as a surfactant and softening agent in a variety of applications.
- It is used as a food ingredient
- Stearic acid is used in the production of cleansers.
- The pearly effect of soaps, cosmetics, and detergents is due to the stearic acid.
Also Read:
Sample Questions
Ques: What is stearic acid's melting point? (1 Mark)
Ans: The melting point of Stearic acid is 69.3 oC.
Ques: What is the use of Stearic acid? (1 Mark)
Ans: Stearic acid is commonly used in shampoos, shaving creams, and detergents to thicken and preserve the form of soaps.
Ques: Is Stearic Acid good for consumption? (2 Mark)
Ans: Stearic acid is a saturated fat that is utilised in a variety of diets. When compared to carbohydrates and other saturated fats, stearic acid is far better to consume since it decreases LDL (low-density lipoproteins) cholesterol, also known as bad cholesterol.
Stearic acid is safe for consumption. Animal fats are the major dietary source of this acid while plant fats provide just a minor contribution. Similarly, there is no evidence that stearic acid consumption causes heart disease, and it has no effect on a person's blood lipid profile during consumption.
Ques: What Is the Effect of Stearic Acid on the Skin? (2 Mark)
Ans: Stearic acid, which is found in soaps and face cleansers, aids in the removal of dirt and bacteria from the skin's surface. Stearic acid's creamy yet waxy texture is very gentle, which is why it's used in body care products. It not only locks in skin's hydration and dryness, but it also protects the skin's surface from water loss via a waxy protective barrier. It also doesn't clog pores and is gentler on sensitive skin, however, if irritation occurs, a sensitivity test should be performed before use. As a result, stearic acid is harmless for the skin.
Ques: Is Stearic Acid Water Soluble? (2 Mark)
Ans: Many organic solvents are soluble in stearic acid. It is mildly soluble in alcohols, phenyls, and alkyl acetates, for example. Carbon tetrachloride, carbon disulfide, and methyl formate are all soluble in the chemical (even known as methyl methanoate). The solubility of stearic acid in dichloromethane at room temperature is approximately 3.58 grammes per 100 grammes of dichloromethane. Stearic acid is not very water-soluble; just a fraction of a milligramme of stearic acid may be dissolved in a hundred grammes of water. Stearic acid is soluble in chloroform at a rate of 15.54 grammes per hundred grammes.
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