Corrosive soda: formula, properties, application

One of the important chemical compounds synthesized by huge batches annually is alkali sodium hydroxide. Such popularity it has earned thanks to its properties. Corrosive soda, the formula of which is NaOH, is of great industrial importance for humans. Consider this substance in more detail.

History of the discovery of matter

For the first time the mention of a compound that resembles caustic soda appears in ancient times. Even the Bible contains some information about the substance neter, extracted from Egyptian lakes. Presumably this was caustic soda.

Aristotle, Plato and other ancient Greek and Roman philosophers and scientists also mention the substance nitrum, which was extracted from natural reservoirs and sold in the form of large variegated pieces (black, gray, white). After all, the methods of cleaning then did not yet know anything, so there was no possibility to separate the connection from the coal polluting it.

In 385 BC we found application of soap making. The process was based on sodium hydroxide. His formula, of course, was not yet known, but it did not stop him from extracting it from the ashes of plants of the genus Solyanka, from lakes and used for cleaning household items, washing clothes, making different soaps.

A little later, the Arabs learned to add essential oils and aromatic substances to the product. Then the soap became beautiful and pleasantly smelling. The active development of processes and technologies of soap making began.

Until the 17th century, caustic soda, whose properties were used to the full, as a chemical compound remained unexplored. It was combined with such substances as soda, potassium hydroxide, potassium carbonate, sodium carbonate . All of them were called caustic alkalis.

Later the scientist Duhamel du Monceau was able to prove the difference of these substances and divided them into alkalis and salts. Since then, caustic soda has received its true and permanent name to this day.

Synonyms of names

It should be noted that the name of this substance is not the same and has several synonyms. In total, you can designate 6 different options:

• sodium hydroxide;
• Sodium hydroxide;
• Caustic soda;
• Sodium alkali;
• caustic;
• Caustic alkali.

This compound is called caustic soda in the common people and industry. In chemical syntheses, it is more correct to speak sodium alkali or sodium hydroxide. The formula does not change from this. The most common name is caustic. The right from the point of view of the systematic nomenclature of substances is the name sodium hydroxide.

Chemical formula and molecule structure

If we consider this substance from the point of view of chemistry, it will consist of two ions: sodium cation (Na ⁺ ) and hydroxide anion (OH-). Binding to each other due to the electrostatic attraction of charged particles, these ions form a corrosive soda. The formula of the empirical form is NaOH.

The hydroxo group is formed by the covalent polar bond between oxygen and hydrogen, while with sodium it is retained by the ionic bond. In solution, alkali completely dissociates into ions, being a strong electrolyte.

Laboratory way of reception

Industrial and laboratory methods of obtaining sodium hydroxide closely intertwine. Often in small quantities it is obtained by chemical and electrochemical methods in smaller installations than at industrial facilities. And tons of substance by the same methods are produced in huge columns of electrolyzers.

There are several basic ways to synthesize caustic in the laboratory.

1. Ferritic method. It consists of two main stages: the first takes place sintering under the influence of high temperature sodium carbonate and ferric oxide (III). As a result, sodium ferrite (NaFeO ₂ ) is formed. In the second stage, it is exposed to water and decomposes to form sodium hydroxide and a mixture of iron and water (Fe ₂ O ₃ * H ₂ O). The resulting caustic soda from the solution is evaporated to crystals or white flakes. Its purity is about 92%.
2. Lime method. It occurs in the reaction between sodium carbonate and calcium hydroxide (hydrated lime) to form calcium carbonate and caustic. The reaction is carried out at a temperature of 80 ° C. As the resulting salt precipitates, it is easily separated. The remaining solution is evaporated and sodium nitrate is obtained.
3. Diaphragm and membrane method of preparation. It is based on the operation of the cell installation. It is fed with a salt solution (NaCL), which is subjected to electrolysis with the formation of free gaseous chlorine and the desired caustic product. The difference between these methods is that with the diaphragm method, the main structural part of the device is the asbestos diaphragm (cathode). With the membrane method, the cathode and anode space is separated by a special membrane.

Thus, sodium hydroxide is obtained in the laboratory, choosing the most advantageous material option. It is, as a rule, less energy-intensive.

Synthesis in industry

How do they get such a substance as sodium hydroxide in industry? The liquid and solid caustic is extracted most often by an electrochemical method. It is based on the electrolysis of a solution of the natural mineral of halite, the vast part of which is formed by table salt.

The main feature of this synthesis is that the by-products together with the caustic soda are gaseous chlorine and hydrogen. The process is carried out in any of three ways:

• Electrolysis diaphragm on a solid cathode;
• With liquid cathode from mercury;
• Membrane with a solid cathode.

The overwhelming majority of the caustic produced in the world is still formed by the membrane method. The resulting alkali is distinguished by a sufficiently high level of purity.

Areas of use

There are quite a few industries in which caustic soda is relevant. The application is based on its chemical and physical properties, making this compound indispensable in many syntheses and processes.

There are several main areas in which sodium hydroxide is an essential element.

1. Chemical production (synthesis of esters, soaps, fats, fiber production, etching of aluminum, for the production of refined products, as a catalyst in many processes, is the main substance for the neutralization of acids and their corresponding oxides, in analytical chemistry is used for titration; Pure metals, many salts, other bases and organic compounds).
2. In the production of paper for processing wood pulp (disposal of wood lignin).
3. In the economic activity of man is also irreplaceable caustic soda. The use of numerous detergents and cleaning products based on it is very important. Soap making, getting shampoos - all this can not do without caustic soda.
4. It is necessary for the synthesis of biofuel.
5. It is used on a national scale for degassing and neutralizing poisonous substances that affect organisms.
6. Manufacture of medicines and narcotic drugs.
7. Food industry - confectionery, chocolate, cocoa, ice cream, coloring of sweets, olives, baking of bakery products.
8. In cosmetology for the removal of foreign formations (moles, papillomas, warts).
9. It is used in alcoholic beverages and tobacco plants.
10. In the textile industry.
11. Production of glass: color, conventional, optical and other.

It is obvious that sodium hydroxide is a very important and useful substance in human activity. It is not for nothing that it is synthesized in the world annually in tons - 57 million or more.

Physical properties

White powdery substance, sometimes colorless. Can be in the form of a fine crystalline powder or in the form of flakes. More often in the form of large crystals. The melting point is quite low - 65.1 ^o C. Very quickly absorbs moisture and passes into the hydrated form of NaOH · 3.5H ₂ O. In this case, the melting point is even less, only 15.5 ^o C. Virtually unlimitedly soluble in alcohols, water . To the touch, both solid and liquid soapy.

Very dangerous in concentrated and diluted form. It can damage all the shells of the eye, up to the optic nerves. Eye contact may result in blindness. Therefore, work with this connection is extremely dangerous and requires protective devices.

Chemical properties

Corrosive properties of sodium show exactly the same as all alkalis: it interacts with acids, acid oxides, amphoteric oxides and hydroxides, salts. From non-metals comes into reaction with sulfur, phosphorus and halogens. Also able to react with metals.

In organic chemistry, sodium hydroxide reacts with amides, ethers, halogen-substituted alkanes.

Storage conditions

Storage of caustic soda is carried out according to certain conditions. This is because it is extremely reactive, especially when the room is wet. The main conditions can be described as follows.

1. Storage away from heaters.
2. Hermetically sealed and sealed packaging, not able to pass moisture.
3. Dry crystalline caustic is stored in bags of special composition (dense polyethylene), liquid - in a dark glass container with ground glass stoppers. If the quantity is large and requires transportation, then a solution of caustic soda is placed in special steel containers and jerricans.

Transport of this substance can be carried out in any known way, observing the safety rules, excluding transportation by air.

Liquid sodium alkali

In addition to crystalline, there is still an aqueous solution of caustic soda. Its formula is the same as for solid. Chemically, the solutions are more applicable and convenient to use. Therefore, in this form, the caustic is used more often.

A solution of caustic soda, the formula of which is NaOH, finds application in all the above areas. It is inconvenient only for transportation, since it is better to transport a dry caustic. For all other properties, it is not inferior to crystals, and in some, it exceeds them.