What Is Citric Acid?
Citric Acid is an organic acid found in citrus fruits and is a type of hydroxy acid with three carboxy groups (-COOH).
It is a clear colorless or white solid, and is available in two forms: anhydrous crystals containing no water molecules, and monohydrate with a single molecule of crystalline water. Both are odorless and have an acidic taste.
Citric Acid appears in the middle of the TCA circuit (citric acid circuit), which breaks down carbohydrates, fats, and proteins into energy substances, and performs important functions. It also has antibacterial properties and the ability to absorb calcium.
Uses of Citric Acid
Citric Acid is widely used in pharmaceutical, food, industrial, and cosmetic applications, depending on its purity.
1. Pharmaceutical Use
Citric Acid for pharmaceutical use is used as an ingredient in preparations for the purpose of buffering, correcting taste, and foaming.
2. Edible Citric Acid
Edible Citric Acid is added to a variety of foods as an acidulant that imparts a fruity sour taste and as a vitamin C stabilizer. It is also used as a dietary supplement to relieve fatigue, reduce muscle pain, increase appetite, and improve liver function.
Furthermore, citric acid is useful as a pH adjuster because of its acidic nature. By adjusting the pH of food, it can inhibit the growth of microorganisms and improve shelf life.
3. Industrial Use
Citric Acid for industrial use is used to clean calcium carbonate, which causes water stains, due to its property of absorbing calcium. It also neutralizes and removes alkaline stains, making it possible to dissolve and remove soap scum.
It is also used in bath salts and bath bombs.
4. For Cosmetics
Citric Acid for cosmetics is used as a pH adjuster, pH buffer, and astringent, taking advantage of its acidic nature. The pH of the skin is slightly acidic (pH 4.5-6), and a change in pH causes skin irritation. pH adjusters can be added to products to maintain a slightly acidic pH.
Astringent action refers to the effect of tightening pores and inhibiting excessive secretion of sweat and sebum.
In addition to citric acid, other acidic substances commonly used are aluminum chloride, alum, and zinc sulfate.
Properties of Citric Acid
1. Physical Properties
Citric Acid is represented by the chemical formula C3H4 (OH) (COOH) 3, has a molecular weight of 192.13, and is a white, odorless crystal or crystalline powder.
It has a flash point of 100°C, a melting point of 153°C, no boiling point, a decomposition temperature of 175°C, an ignition point of 1010°C, and an explosive range of 1.9 vol/% lower and 4.8 vol/% upper. Its density is 1.665 g/cm3 and pH of 2% aqueous solution is about 2.0.
2. Chemical Properties
With a solubility of 59.2 g/100 g (at 20°C), it is extremely soluble in water and highly hygroscopic. It is also soluble in ethanol.
Although stable under normal handling conditions, it may react violently when in contact with strong oxidizing agents or strong alkaline agents. In addition, its aqueous solution is acidic, and thus has a high potential to corrode metals.
It decomposes at 175°C and converts to aconitic acid. If mixed with air at a certain rate in powder form, there is a risk of dust explosion.
Other Information on Citric Acid
1. Safety of Citric Acid
Citric Acid is a very safe compound, as it is used for both food and cosmetic applications. On the other hand, it is a strong eye irritant and can cause respiratory irritation if inhaled in large quantities, so care should be taken when handling it to avoid contact with the eyes and inhalation of large quantities.
2. Handling Citric Acid
When handling citric acid, wear protective gloves, protective clothing, protective glasses, and a protective mask, and work in a well-ventilated area. It is important to wash hands thoroughly after handling.
Keep the storage area clean to prevent product contamination, and store away from direct sunlight, high temperatures, and high humidity. Since the product is highly hygroscopic, the container should be sealed and stored in a dry place to avoid moisture absorption.
Avoid contact with strong oxidizing agents, strong alkaline agents, and metals, which are hazardous substances that can cause color mixing, and store in polyethylene, polypropylene, glass, etc.