Lactic acid is produced by muscles during intense exercise, causing fatigue. It can also be found in fermented foods like yogurt, and is used in skincare products for exfoliation.
| IUPAC Name | 2-Hydroxypropanoic acid |
| Molecular Formula | C3H6O3 |
| CAS Number | 50-21-5 |
| Synonyms | Milk acid, 2-Hydroxypropionic acid, DL-Lactic acid |
| InChI | InChI=1S/C3H6O3/c1-2(4)3(5)6/h2,4H,1H3,(H,5,6) |
Lactic Acid Properties
Lactic Acid Formula
The chemical formula of milk acid is C3H6O3. It consists of three carbon atoms, six hydrogen atoms, and three oxygen atoms. This formula represents the arrangement and types of atoms present in a molecule of milk acid.
Lactic Acid Molar Mass
The molar mass of milk acid is approximately 90.08 grams per mole. It is calculated by adding up the atomic masses of all the atoms present in one molecule of milk acid.
Lactic Acid Boiling Point
Lactic acid has a boiling point of around 122-135 degrees Celsius. At this temperature, milk acid changes from a liquid state to a gaseous state. The boiling point can vary depending on the purity and concentration of milk acid.
Lactic Acid Melting Point
The melting point of milk acid is approximately 17-18 degrees Celsius. At this temperature, milk acid undergoes a phase change from a solid to a liquid state. The melting point can vary slightly based on the specific form of milk acid.
Lactic Acid Density g/mL
The density of milk acid is about 1.2 grams per milliliter (g/mL). This density value indicates the mass of milk acid present in a given volume. It is an important characteristic used to determine the concentration of milk acid solutions.
Lactic Acid Molecular Weight
The molecular weight of milk acid is approximately 90.08 grams per mole. It represents the sum of the atomic weights of all the atoms in a molecule of milk acid. The molecular weight is used in various calculations and chemical analyses.
Lactic Acid Structure
Lactic acid has a structure consisting of three carbon atoms bonded to each other in a chain, with a hydroxyl (-OH) group attached to one carbon and a carboxyl (-COOH) group attached to another carbon. This structure is responsible for the acidic properties of milk acid.
Lactic Acid Solubility
Lactic acid is soluble in water and forms a clear, colorless solution. It readily dissolves due to its ability to form hydrogen bonds with water molecules. The solubility of milk acid can vary depending on factors such as temperature and concentration.
| Appearance | Colorless liquid |
| Specific Gravity | 1.2 g/mL |
| Color | Colorless |
| Odor | Slightly acidic odor |
| Molar Mass | 90.08 g/mol |
| Density | 1.2 g/mL |
| Melting Point | 17-18 °C |
| Boiling Point | 122-135 °C |
| Flash Point | 79 °C |
| Water Solubility | Fully miscible |
| Solubility | Soluble in ethanol, Water and ether |
| Vapour Pressure | 3.03 mmHg at 25 °C |
| Vapour Density | 2.55 (air=1) |
| pKa | 3.86 |
| pH | Approximately 2.4-3.4 |
Lactic Acid Safety and Hazards
Milk acid poses some safety concerns and hazards. It is considered a mild irritant to the skin, eyes, and respiratory system. Direct contact can cause irritation, redness, and discomfort. Ingestion of concentrated milk acid can lead to abdominal pain, nausea, and vomiting. It is important to handle milk acid with caution and use appropriate protective measures, such as gloves and goggles. In case of skin or eye contact, rinsing with plenty of water is recommended. Additionally, proper ventilation should be ensured when working with milk acid to prevent inhalation of vapors.
| Hazard Symbols | Corrosive (C), Irritant (Xi) |
| Safety Description | Wear protective gloves and eye/face protection. Avoid breathing vapors. Avoid release to the environment. |
| UN IDs | UN3265 |
| HS Code | 2918.12.00 |
| Hazard Class | Class 8 (Corrosive) |
| Packing Group | PG III |
| Toxicity | Lactic acid is considered to have low acute toxicity. It may cause irritation and burns to the skin and eyes. Inhalation of vapors may cause respiratory irritation. Ingestion of concentrated milk acid can cause gastrointestinal irritation. Proper handling and safety precautions should be followed to minimize potential risks. |
Lactic Acid Synthesis Methods
There are several methods to synthesize milk acid.
One common method is the fermentation of carbohydrates by milk acid bacteria. In this process, microorganisms convert sugars, such as glucose or lactose, into milk acid through anaerobic metabolism. This fermentation occurs naturally in foods like yogurt, sauerkraut, and pickles.
Another method involves chemical synthesis using acetaldehyde as a starting material. Acetaldehyde undergoes a reaction with cyanide ions, resulting in the formation of lactonitrile. Afterward, hydrolysis occurs, leading to the conversion of lactonitrile into milk acid. This method requires careful handling and control of reaction conditions.
Scientists actively produce milk acid through bioengineering techniques by genetically modifying bacteria like Escherichia coli. They engineer these bacteria to express enzymes that convert glucose or other sugars into milk acid. This method allows for the production of milk acid on a larger scale and with greater control over the process.
Lactic acid is derived from renewable resources such as corn or sugarcane by chemically hydrolyzing starch or cellulose present in these plant materials into glucose. Microbial or enzymatic action then ferments the glucose into milk acid.
Each of these methods has its advantages and limitations in terms of cost, scalability, and environmental impact. The choice of synthesis method depends on the specific application and desired properties of milk acid.
Lactic Acid Uses
Milk acid finds numerous applications across various industries. Here are some common uses:
- Food and Beverage Industry: Milk acid acts as a natural preservative, acidity regulator, and flavor enhancer in food products like dairy, bakery, and beverages. It contributes to the tangy taste of yogurt and imparts a sour flavor to sourdough bread.
- Pharmaceutical Industry: Milk acid actively contributes to the production of pharmaceuticals, including drugs, ointments, and creams. It serves as a pH adjuster and stabilizer in formulations, enhancing their efficacy and shelf life.
- Skincare and Cosmetics: Milk acid is a key ingredient in skincare products due to its exfoliating properties. It helps remove dead skin cells, promoting a smoother and brighter complexion. Anti-aging creams and lotions actively utilize it as an ingredient.
- Textile Industry: In the textile industry, milk acid actively assists in dyeing and regulates pH during the dyeing and printing processes. It aids in improving color fastness and dye penetration.
- Bioplastics: Milk acid is a precursor for the production of biodegradable polymers such as polymilk acid (PLA). Companies widely use PLA in packaging materials, disposable cutlery, and other eco-friendly products.
- Cleaning Products: Cleaning products utilize milk acid as a potent natural disinfectant and descaler. It helps remove mineral deposits and stains from surfaces, making it an environmentally friendly alternative to harsh chemicals.
- Industrial Applications: Milk acid serves as a raw material for the synthesis of various chemicals, including lactates, solvents, and biodegradable plastics.
The versatile nature of milk acid makes it a valuable ingredient across diverse industries, contributing to the development of sustainable and functional products.
Questions:
Q: What is lactic acid?
A: Milk acid is a compound produced by the muscles during intense exercise or fermentation of sugars by microorganisms, found in fermented foods like yogurt.
Q: Where does lactic acid fermentation occur?
A: Milk acid fermentation occurs in various organisms, including bacteria, fungi, and our own muscle cells.
Q: What is lactic acid fermentation?
A: Milk acid fermentation is a metabolic process that converts sugars into lactic acid, occurring in the absence of oxygen, resulting in energy production.
Q: What does lactic acid do?
A: Milk acid contributes to muscle fatigue and soreness, regulates acidity levels in the body, and serves as an intermediate in various biochemical pathways.
Q: Which is a commercial use for lactic acid fermentation?
A: Milk acid fermentation is commercially used in the production of yogurt, sauerkraut, pickles, and other fermented foods.
Q: How to get rid of lactic acid?
A: Gentle exercise, adequate hydration, and stretching can help in the removal and breakdown of lactic acid from muscles.
Q: Where is lactic acid found?
A: Milk acid is found in various natural sources, such as dairy products, fermented foods, and the muscles of animals.
Q: How to reduce lactic acid in the body?
A: To reduce milk acid buildup, one can incorporate proper warm-up and cool-down routines, maintain a balanced diet, and gradually increase exercise intensity over time.