A typical bottle of food vinegar that you canfind in the kitchen of any housewife, has in the composition of many other acids and vitamins. Adding a couple of drops of the product to cooked food, salads causes a natural enhancement of taste. But few of us really thought about the properties and real scales of the application of the main component - acetic acid.
The formula of acetic acid CH3COOH, which relates it to a number of fatty carboxylic acidsacids. The presence of one carboxyl group (COOH) refers to monobasic acids. The substance is found on the globe in organic form and is obtained synthetically in laboratories. Acid is the simplest, but no less important representative of its series. Easily soluble in water, hygroscopic.
The physical properties of acetic acid and density vary depending on the temperature regime. At room temperature in 20aboutC acid is in the liquid state, has a density of 1.05 g / cm3. Has a specific smell and sour taste. The solution of the substance without impurities hardens and passes into crystals at a temperature below 17aboutC. The process of boiling acetic acid begins at a temperature above 117aboutC. The methyl group (CH3) of the formula of acetic acid is obtained by the interaction of alcohols with oxygen: fermentation of alcohol substances and carbohydrates, souring of wines.
The discovery of vinegar was one of the first in the seriesacids and was carried out in stages. Initially, acetic acid began to be extracted by distillation of Arab scientists of the 8th century. However, even in ancient Rome, this substance, derived from sour wine, was used as a universal sauce. The name itself from Ancient Greek is translated as "sour". In the 17th century, scientists in Europe managed to extract a pure substance of matter. At that time, they derived the formula and found an unusual ability - Acetic acid in the vapor state was ignited by blue fire.
Until the 19th century, scientists found the presence ofacetic acid only in the organic form - as part of the compounds of salts and esters. In the composition of plants and their fruits: apples, grapes. In the body of humans and animals: sweat secretions, bile. At the beginning of the 20th century, Russian scientists accidentally extracted acetic aldehyde from the reaction of acetylene with mercury oxide. For today, the consumption of acetic acid is so great that its main production takes place only in a synthetic way on a huge scale.
Will there be pure acetic acid or with the presence of impurities in the solution depends on the method of extraction.Food acetic acid is obtained by a biochemical method in the process of ethanol fermentation. In industry, several ways of extracting acid are isolated. As a rule, reactions are accompanied by a high temperature and the presence of catalysts:
The industrial way is more efficient and economicalbiochemical. Thanks to the industrial method, the volume of production of acetic acid in the 20-th and 21-st century has grown hundreds of times, compared with the 19th century. For today, the synthesis of acetic acid by carbonylation of methanol gives more than 50% of the total volume produced.
In the liquid state, acetic acid is colorless.The acidity level of pH 2,4 is easily checked with a litmus test. Acetic acid when it hits the indicator stains it red. The physical properties of acetic acid vary visually. When the temperature drops below 16aboutC, the substance takes a solid form and resemblessmall crystals of ice. It dissolves easily in water and interacts with a wide range of solvents, except hydrogen sulphide. Acetic acid reduces the total volume of the liquid when diluted with water. Independently describe the physical properties of acetic acid, its color and consistency, which you observe in the following image.
The substance ignites at a temperature of 455aboutWith the release of heat in 876 kJ / mol.The molar mass is 60.05 g / mol. The physical properties of acetic acid as an electrolyte in reactions are weak. The permittivity is 6.15 at room temperature. Pressure, like density, - variable physical value of acetic acid. At a pressure of 40 mm. gt; Art. and temperature 42aboutC will begin the process of boiling. But already at a pressure of 100 mm. gt; Art. The boiling occurs only at 62aboutFROM.
Reacting with metals and oxides,the substance shows its acid properties. Perfectly dissolving more complex compounds, the acid forms salts, which are called acetates: magnesium, lead, potassium, etc. The pK acid value is 4.75.
When interacting with gases, vinegar enters intosubstitution reaction with subsequent displacement and formation of more complex acids: chloroacetic, iodoacetic. Dissolving in water, the acid dissociates with the release of acetate ions and hydrogen protons. The degree of dissociation is 0.4 percent.
Physical and chemical properties of aceticacids in a crystalline form create diamers on hydrogen bonds. Also, its properties are needed when creating more complex fatty acids, steroids and sterol biosynthesis.
Detect acetic acid in solution foraccount for the identification of its physical properties, for example smell. It is enough to add a stronger acid to the solution, which will begin to displace the salts of vinegar with the release of its vapors. By laboratory distillation of CH3COONa and H2CO4 it is possible to obtain acetic acid in dry form.
We will draw experience from the school program on chemistry 8class. The physical properties of acetic acid clearly demonstrate the chemical reaction of dissolution. It is enough to add copper oxide into the solution to the substance and lightly heat it. Oxide completely dissolves, making a solution of bluish color.
Qualitative reactions of the substance with manysolutions form: esters, amides and salts. However, during the manufacture of other substances, the requirements for the physical properties of acetic acid remain high. It should always have a high degree of dissolution, and therefore, do not have third-party impurities.
Depending on the concentration of acetic acidaqueous solution, a number of its derivatives are isolated. The concentration of the substance more than 96% has the name - glacial acetic acid. Acetic acid in 70-80% can be purchased at grocery stores, where it will be called - acetic essence. Table vinegar has a concentration of 3-9%.
In addition to food specialties, acetic acidhas a number of physical properties, to which mankind has found its application in everyday life. A solution of a substance of low concentration easily removes plaque from metal products, the surface of mirrors and windows. The ability to absorb moisture also plays good. Vinegar well removes smells in musty premises, removes stains from vegetables and fruits on clothing.
As it turned out, the physical property of acetic acid - To remove fat from the surface - can findapplication in folk medicine and cosmetology. A weak solution of food vinegar is treated with hair to give them shine. The substance is widely used to treat colds, remove warts and skin fungi. The use of vinegar as part of cosmetic wraps to fight cellulite is gaining momentum.
In compounds of salts and other complex substances, acetic acid is an indispensable element:
Annually production of acetic acidincreases. Today its volume in the world is more than 400 thousand tons per month. The acid is transported in strong steel tanks. Storage in plastic containers at many production facilities in connection with the high physical and chemical activity of acetic acid is prohibited or limited to a period of several months.
Acetic acid of high concentration hasthird degree of ignition and releases toxic fumes. It is recommended to wear special gas masks and other personal protective equipment while working with acid. A lethal dose for the human body from 20 ml. At the time of ingestion, the acid first burns the mucous membrane, and then affects the other organs. In such cases, immediate hospitalization is needed.
After getting acid on the exposed areas of the skin, it is recommended to immediately wash them with running water. Surface burn with acid can cause tissue necrosis, which also requires hospitalization.
Scientists of physiology have found out, that to the person at allRequired acetic acid - without food additives can do without. But people with acid intolerance, as well as with stomach problems, the substance is contraindicated.
Acetic acid is used in book printing.
The substance was found in small quantities in honey, bananas and wheat.
Cooling the acetic acid and vzboltav with a container, you can observe its sharp congealing.
A small concentration of acetic acid can reduce the pain symptom from an insect bite, as well as minor burns.
Admission to food products with low content of acetic acid reduces the level of cholesterol in the body. The substance stabilizes the level of sugar in diabetics well.
The use of protein and carbohydrate food together with a small amount of acetic acid increases their digestibility by the body.
If the food is salted, just add a few drops of vinegar to smooth the salty.
Millennium use of acetic acidled to the fact that its physical and chemical properties find their application at every step. Hundreds of possible reactions, thousands of useful substances, thanks to which humanity goes further. The main thing is to know all the characteristics of acetic acid, its positive and negative qualities.
Do not forget about the benefits, but you always needremember what harm can cause careless handling of acetic acid of high concentration. By its peril, it stands next to hydrochloric and sulfuric acid. Always remember about safety when using acid. Properly and carefully dilute the essence with water.
