Salts are divided into medium, acidic, basic, double and mixed. All of them are widely used in everyday life, but even more - in industry. Understanding the classification of salts makes it possible to understand the basics of chemistry.
How to classify salts
First, let us define salts. They are chemical compounds in which a metal atom is connected to an acid residue. Unlike other classes of substances, salts are characterized by an ionic chemical bond.
Representatives of this class are divided into several groups with specific features.
Normal salts
Middle salts in their composition have only cations of a certain metal and an acid residue. As an example of such compounds, sodium chloride, potassium sulfate can be mentioned. This group is considered the most common in the earth's crust. Among the methods for their preparation, we note the neutralization process between acid and base.
Acid salts
This group of compounds consists of metal, hydrogen, and an acid residue. Polybasic acids form such compounds : phosphoric, sulfuric, carbonic. As an example of an acid salt that is widespread in everyday life, sodium bicarbonate (baking soda) can be noted. Such substances are obtained by the interaction between the middle salt and the acid.
Basic salts
In these compounds, there are metal cations, a hydroxyl group, as well as anions of the acid residue. An example of a basic salt is calcium hydroxychloride.
Mixed salts
Double salts mean the presence of two metals that replace hydrogen in acid. The formation of substances of a similar composition is characteristic of polybasic acids. For example, two active metals are present in sodium potassium carbonate at once. Double mixed salts are important for the chemical industry, are widely used in everyday life.
Features of Mixed Salts
Double salts of potassium and sodium are found in nature in the form of sylvinite. Potassium is also able to form mixed salts with aluminum.
Mixed (double) salts are compounds that consist of various anions or cations. For example, bleach has in its composition an anion of hypochlorous and hydrochloric acid.
Of particular interest are double ammonium salts. Most of the resulting substances are used as mineral fertilizers.
Obtaining double ammonium salts is carried out by the interaction of ammonia with polybasic acids. Diammonium phosphates are in demand in the manufacture of flame retardants (flame retardants). Impurity-free double salts are required in the pharmaceutical and food industries.
Ammonium zinc, magnesium phosphates are of industrial importance. Due to the insignificant solubility in water, such salts act as flame retardants in paints and plastics.
These double salts are suitable for impregnating fabrics and wood, protecting surfaces from high humidity. Iron and aluminum ammonium phosphates are an excellent tool to protect metal structures from natural corrosion processes.
Examples of double salts of technical importance can be given for iron and zinc. They are a breeding ground for the cultivation of yeast, are in demand in the manufacture of matches, the production of insulating materials, mica.
Getting
Double ammonium salts are obtained by thermal saturation of phosphoric acid with ammonia and a certain alkali. Dimmonium phosphate is of industrial interest. It is produced by heat treatment with ammonia phosphoric acid. A successful process requires a temperature of about 70 degrees Celsius. The technology involves the formation of precipitated aluminum and iron phosphates, which also find their industrial application.
Some difficulties arise with the names of double salts due to the fact that they contain yes an acid residue, or two cations.
Magnesium ammonium phosphate is in demand in the chemical industry, so the technology for its creation has certain features. Extraction of phosphoric acid, which is mixed with magnesium phosphate, is carried out by neutralization with gaseous ammonia.
Complex compounds
There are certain differences between complex and double salts. Let's try to find out the features of complex salts. In their composition, the presence of a complex ion, which is enclosed in square brackets, is assumed. In addition, a complexing agent (central ion) is present in such compounds. It is surrounded by particles called ligands. Complex salts are characterized by stepwise dissociation. The first step is the formation of a complex ion in the form of a cation or anion. Next, there is a partial dissociation of the complex ion into a cation and ligands.
Features of the salt range
Given that there are many different types of salts, their nomenclature is of interest. For medium salts, the name is formed on the basis of anion (chloride, sulfate, nitrate), to which the Russian name of the metal is added. For example, CaCO3 is calcium carbonate.
For acid salts, the addition of a hydro-prefix is characteristic. For example, KHCO3-potassium bicarbonate.
The nomenclature of basic salts implies the use of a prefix hydroxy. So, the salt of Al (OH) 2Cl is called aluminum dihydroxochloride.
In the name of double salts containing two cations, you must first give the name to the anion, then list both metals that make up the compound.
More complex names are characteristic of complex compounds. In chemistry, there is a special section that deals with the study of such salts.
If we analyze the physical properties of different representatives of double salts, it can be noted that they differ significantly in their ability to dissolve in water. Among the double salts there are examples of substances having good solubility, for example, sodium chloride, potassium. Among the sparingly soluble compounds, double salts of phosphoric and silicic acids can be mentioned.
By chemical properties, double salts are similar to normal (medium), able to interact with acids and other salts.
Ammonium nitrates and salts undergo thermal decomposition, forming several reaction products.
In the case of electrolytic dissociation of such compounds, residue anions and metal cations can be obtained. For example, when decaying to aluminum ions of potassium alum, aluminum and potassium cations, as well as sulfate ions can be found in solution.
Separation of the salt mixture
Given that two metals are contained in natural minerals at once, the need arises for their separation. Among the many methods for separating salt mixtures, fractional crystallization can be distinguished. This method involves the preliminary melting of the double salt, its subsequent division into different compounds, then crystallization. This option for the separation of mixtures is associated with the physical characteristics of substances. When the mixture is separated by chemical methods, reagents are selected that are qualitative for certain cations or anions. After the precipitation of some parts of the double salt, the precipitates are removed.
If it is necessary to separate a three-component system in which there is a solid phase, and emulsions are also present, centrifugation is carried out.
Conclusion
Double salts differ from other types of salts by the presence of two metals in the formula. In pure form, such compounds are rarely used, mainly they are initially separated by physical or chemical methods, and only then they are used in various fields of industrial production. Double salts are also used in the chemical industry as a source of obtaining many popular chemicals.