Tartaric acid is a naturally occurring organic acid found in various plants, particularly in grapes. It is widely used in the food and beverage industry, especially in winemaking and baking, due to its acidic properties and ability to stabilize certain ingredients. Tartaric acid is also used in the pharmaceutical and cosmetic industries. Chemical Properties 1. Structure: o Tartaric acid is a dicarboxylic acid with two carboxyl groups (-COOH) attached to a central carbon atom that is also bonded to a hydroxyl group (-OH). This gives it the formula HOOC-CHOH-COOH. o The molecule has two stereocenters, leading to the existence of several isomers, including the naturally occurring L-tartaric acid, which is the most common form used in industry. 2. Solubility: o Tartaric acid is moderately soluble in water, with a solubility of about 14 g/100 mL at room temperature. o It is also soluble in alcohols such as ethanol but has limited solubility in non-polar solvents. 3. Acidity: o Tartaric acid is a weak diprotic acid with two acidic protons. Its first dissociation constant (pKa₁) is approximately 2.98, and the second dissociation constant (pKa₂) is around 4.33. o The presence of two carboxyl groups allows tartaric acid to donate two protons in aqueous solutions, making it relatively acidic compared to many other organic acids. 4. Optical Activity: o Tartaric acid exhibits optical activity due to its chiral centers. The naturally occurring form, L-tartaric acid, is optically active and rotates plane-polarized light to the left. o Its optical activity is crucial in the context of enantioselective reactions and in differentiating between various isomers in analytical chemistry.

Glycolic acid is the simplest alpha-hydroxy acid (AHA) and is widely used in skincare products due to its effective exfoliating properties. It is naturally derived from sugar cane but can also be synthesized. Glycolic acid is highly valued in dermatology and cosmetics for its ability to improve skin texture and tone. Chemical Properties 1. Structure: o Glycolic acid has a simple structure with two carbon atoms. The molecule consists of a hydroxyl group (-OH) attached to the alpha carbon, which is adjacent to the carboxylic acid group (-COOH). o The presence of both the hydroxyl and carboxylic acid groups gives glycolic acid its unique chemical properties. 2. Solubility: o Glycolic acid is highly soluble in water, which makes it easy to formulate in aqueous-based skincare products. o It is also soluble in alcohols and some organic solvents, but its solubility in non-polar solvents is limited. 3. Acidity: o Glycolic acid is a relatively strong acid among AHAs, with a pKa of around 3.83. This indicates that it readily dissociates in water to release hydrogen ions (H+), contributing to its acidic nature. o When used in skincare, the pH of glycolic acid formulations is usually adjusted to ensure safety and efficacy, often ranging between 3.0 and 4.0. 4. Exfoliating Properties: o Glycolic acid’s small molecular size allows it to penetrate the skin more easily than other AHAs. It works by breaking down the bonds between dead skin cells, promoting their removal and revealing fresher, smoother skin underneath. o This property makes it effective in treating various skin conditions such as hyperpigmentation, fine lines, acne, and uneven skin texture. 5. Hygroscopic Nature: o Glycolic acid is hygroscopic, meaning it can attract and retain moisture from the environment. This property can help increase skin hydration when used in lower concentrations in skincare products. 6. Chemical Reactivity: o Glycolic acid can react with bases to form glycolate salts, which are sometimes used in different industrial and cosmetic applications. o It can also undergo esterification reactions with alcohols, producing glycolic esters, which may be used in some formulations.

Lactic acid is an organic acid that plays a crucial role in various biological processes and is widely used in the food, pharmaceutical, and cosmetic industries. It is naturally produced in the body during anaerobic respiration and is found in fermented foods like yogurt and sourdough bread. Lactic acid is also a key ingredient in skincare products due to its exfoliating and hydrating properties. Chemical Properties 1. Structure: o Lactic acid is a hydroxycarboxylic acid with a hydroxyl group (-OH) and a carboxyl group (-COOH) attached to the same carbon atom, making it an alpha-hydroxy acid (AHA). o It exists in two optical isomers: L-lactic acid (L-enantiomer) and D-lactic acid (D-enantiomer), with L-lactic acid being the form commonly found in the human body. 2. Solubility: o Lactic acid is highly soluble in water, which makes it easy to incorporate into aqueous formulations for various applications. o It is also soluble in ethanol and other polar organic solvents, although it is less soluble in non-polar solvents. 3. Acidity: o Lactic acid is a weak acid with a pKa of approximately 3.86, indicating that it partially dissociates in water to release hydrogen ions (H+), contributing to its acidic nature. o Its acidity allows it to lower the pH of solutions, making it useful in products designed to exfoliate the skin or preserve food. 4. Hygroscopic Nature: o Lactic acid is hygroscopic, meaning it has the ability to attract and retain moisture from the environment. This property makes it valuable in skincare products for its moisturizing and humectant effects.

Sodium hydroxide, commonly known as caustic soda or lye, is a highly caustic and corrosive inorganic compound. It is widely used in various industrial processes, including the manufacture of paper, textiles, and detergents, as well as in water treatment and chemical synthesis. Sodium hydroxide is known for its strong basic (alkaline) properties and is a key ingredient in many chemical reactions and products. Chemical Properties 1. Structure: o Sodium hydroxide is an ionic compound composed of sodium (Na⁺) cations and hydroxide (OH⁻) anions. o The hydroxide ion is responsible for its strong basicity, while the sodium ion balances the charge, making it a neutral compound overall. 2. Solubility: o Sodium hydroxide is highly soluble in water, dissolving readily to form a strongly alkaline solution. The dissolution of NaOH in water is exothermic, meaning it releases a significant amount of heat. o It is also soluble in ethanol and methanol but is insoluble in non-polar solvents like ether. 3. Basicity: o Sodium hydroxide is a strong base, meaning it completely dissociates into sodium ions (Na⁺) and hydroxide ions (OH⁻) in water. This complete dissociation results in a high pH, typically around 14 for concentrated solutions, making it extremely alkaline. o The hydroxide ions are highly reactive and can neutralize acids, forming water and a corresponding salt. This reaction is fundamental to many of its applications in industry and laboratory settings. 4. Reactivity: o Sodium hydroxide is highly reactive, especially with acids and acidic compounds. When it reacts with acids, it forms water and a salt in a neutralization reaction. For example, reacting NaOH with hydrochloric acid (HCl) produces sodium chloride (table salt) and water: NaOH+HCl→NaCl+H2O\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}NaOH+HCl→NaCl+H2O

Citric acid is a weak organic acid that is naturally found in citrus fruits such as lemons, limes, and oranges. It is a key intermediate in the citric acid cycle (Krebs cycle), which is essential for cellular respiration in all aerobic organisms. Chemical Properties 1. Structure: o Citric acid has three carboxyl (-COOH) groups and one hydroxyl (-OH) group attached to a central carbon chain. This structure allows it to function as a tricarboxylic acid. 2. pH and Acidity: o It is a weak acid with a pKa of 3.13 for the first dissociation, 4.76 for the second, and 6.40 for the third. In aqueous solutions, it partially dissociates, contributing to its acidity. 3. Solubility: o Citric acid is highly soluble in water, with a solubility of approximately 148 grams per 100 milliliters at room temperature. It is also soluble in ethanol but less so in organic solvents like acetone or ether. 4. Chelating Properties: o It acts as a chelating agent, meaning it can bind to metal ions, such as calcium or magnesium, forming complexes. This property is useful in water softening, food preservation, and cosmetics. 5. Thermal Decomposition: o When heated, citric acid decomposes at temperatures above 175°C, releasing carbon dioxide and water, and leaving behind a residue of carbon. This property is useful in some industrial processes where controlled thermal decomposition is required. 6. Buffering Capacity: o Due to its multiple carboxyl groups, citric acid can act as a buffer, helping to maintain a stable pH in solutions. This makes it useful in pharmaceuticals, food, and cosmetic formulations. 7. Reactivity: o Citric acid can react with bases to form salts, known as citrates. These salts, such as sodium citrate or potassium citrate, are often used as emulsifiers, preservatives, or pH regulators. 8. Oxidation: o Although relatively stable, citric acid can be oxidized to form carbon dioxide and water in the presence of strong oxidizing agents.