One of the important chemical compounds synthesized in huge batches every year is alkali sodium hydroxide. It has earned such popularity due to its properties. Caustic soda, whose formula is NaOH, is of great industrial importance to humans. Consider this substance in more detail.
Discovery History
For the first time, mentions of a compound resembling caustic soda in properties appear even in ancient times. Even the Bible contains some information about the neter material obtained 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 pieces of different colors (black, gray, white). After all, they did not know anything about the cleaning methods then, so there was no possibility to separate the compound from the coal polluting it.
In 385 BC, soap making was used. The process was based on caustic soda. His formula, of course, was not yet known, but this did not prevent him from extracting from the ashes of plants of the Solyanka genus, from lakes and using it for cleaning household items, washing clothes, and making various 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 soap making processes and technologies began.
Until the 17th century, caustic soda, the properties of which were used with might and main, remained unexplored as a chemical compound. It was combined with substances such as soda, potassium hydroxide, potassium carbonates, sodium. All of them were called caustic alkalis.
Later, the scientist Duhamel du Monceau was able to prove the difference between these substances and divided them into alkalis and salts. Since then, caustic soda has received its true and constant name to this day.
Name synonyms
It should be noted that the name of this substance is not the same and has several synonyms. In total, 6 different options can be identified:
- sodium hydroxide;
- caustic soda;
- caustic soda;
- sodium alkali;
- caustic;
- caustic alkali.
Caustic soda, this compound is called in common people and industry. In chemical syntheses, it is more correct to say sodium alkali or caustic soda. The formula does not change from this. The most common name is caustic. Correct from the point of view of a systematic nomenclature of substances is the name sodium hydroxide.
The chemical formula and structure of the molecule
If we consider this substance from the point of view of chemistry, then it will consist of two ions: sodium cation (Na + ) and hydroxide anion (OH - ). Contacted by electrostatic attraction of uncharged particles, these ions form caustic soda. The empirical formula is NaOH.
The hydroxy group is formed by a covalent polar bond between oxygen and hydrogen, while with sodium it is held by an ionic bond. In solution, the alkali completely dissociates into ions, being a strong electrolyte.
Laboratory method of obtaining
Industrial and laboratory methods for producing caustic soda closely overlap. Often in small quantities it is obtained by chemical and electrochemical methods in smaller plants than in industrial facilities. And tons of material are produced in the same way in huge columns of electrolyzers.
There are several basic methods for synthesizing caustic in the laboratory.
- Ferritic method. It consists of two main stages: at the first, sintering under the influence of high temperature of sodium carbonate and iron oxide (III) occurs. As a result, sodium ferrite (NaFeO 2 ) is formed. At 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 sodium hydroxide from the solution is evaporated to white crystals or flakes. Its purity is approximately 92%.
- The calcareous method. It consists in the interaction between sodium carbonate and calcium hydroxide (slaked lime) with the formation of calcium carbonate and caustic. The reaction is carried out at a temperature of 80 about C. Since the salt formed precipitates, it is easily separated. The remaining solution was evaporated to give sodium alkali.
- Diaphragm and membrane production method. Based on the installation of the electrolyzer. It is supplied with a solution of sodium chloride (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). In 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 option in material terms. He, as a rule, is less energy consuming.
Synthesis in industry
How is a substance such as caustic soda obtained in industry? Liquid and solid caustic is extracted most often by the electrochemical method. It is based on the electrolysis of a solution of the natural mineral halite, the vast majority of which is formed by sodium chloride.
The main feature of this synthesis is that gaseous chlorine and hydrogen are by-products along with sodium hydroxide. The process is carried out in any of three options:
- solid-cathode diaphragm electrolysis;
- with a liquid cathode of mercury;
- membrane with a solid cathode.
The vast majority of caustics produced in the world are still formed by the membrane method. The resulting alkali is characterized by a fairly 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 indispensable element.
- Chemical production (synthesis of esters, soaps, fats, fiber production, etching of aluminum, to obtain oil products, as a catalyst in many processes; is the main substance for neutralizing acids and their corresponding oxides; in analytical chemistry it is used for titration; it is also used to obtain pure metals, many salts, other bases and organic compounds).
- In the manufacture of paper for the treatment of wood pulp (disposal of lignin from wood).
- Caustic soda is also indispensable in human activities. The use of numerous detergents and cleaners based on it is very important. Soap making, getting shampoos - all this does not do without caustic soda.
- Essential for biofuel synthesis.
- It is used on a national scale for the degassing and neutralization of toxic substances that affect organisms.
- Production of drugs and drugs.
- Food industry - confectionery, chocolate, cocoa, ice cream, coloring sweets, olives, baking bakery products.
- In cosmetology to remove foreign formations (moles, papillomas, warts).
- Used in distilleries and tobacco plants.
- In the textile industry.
- Glass production: color, ordinary, optical and other.
Obviously, sodium hydroxide is a very important and useful substance in human activity. It is not in vain that it is synthesized in the world annually in tons - 57 million or more.
Physical properties
White powdery substance, sometimes colorless. It 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 ° C. It absorbs moisture very quickly and passes into the hydrated form of NaOH · 3.5 N 2 O. In this case, the melting point is even lower, only 15.5 ° C. It dissolves almost unlimitedly in alcohols and water . To the touch, both solid and liquid soapy.
Very dangerous in concentrated and diluted form. It can damage all membranes of the eye, up to the optic nerves. Eye contact may result in blindness. Therefore, working with this connection is extremely dangerous and requires protective devices.
Chemical properties
The caustic soda properties are exactly the same as all alkalis: it interacts with acids, acid oxides, amphoteric oxides and hydroxides, salts. From non-metals it reacts with sulfur, phosphorus and halogens. Also capable of reacting with metals.
In organic chemistry, sodium hydroxide interacts with amides, esters, halogen-substituted alkanes.
Storage conditions
Storage of caustic soda is carried out under certain conditions. This is because it is extremely reactive, especially when the room is wet. The main conditions are the following.
- Storage away from heating appliances.
- Hermetically sealed and sealed packaging, not able to pass moisture.
- Dry crystalline caustic is stored in bags of a special composition (dense polyethylene), liquid - in a dark glass container with ground stoppers. If its quantity is large and requires transportation, then the caustic soda solution is placed in special steel containers and canisters.
This substance can be transported in any known manner in compliance with safety regulations, 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, caustic is used more often.
A solution of caustic soda, the formula of which is NaOH, is used in all of the above areas. It is inconvenient only during transportation, since it is better to transport dry caustic. In all other properties it is in no way inferior to crystals, and in some it surpasses them.