Basic salts are examples of formulas. Table salt formula
Salts are complex substances that are the product of complete or incomplete replacement of hydrogen atoms of an acid with metal atoms, or replacement of hydroxyl groups of a base with an acidic residue.
Depending on the composition, salts are divided into medium (Na2SO4, K3PO4), acidic (NaHCO3, MgHPO4), basic (FeOHCl2, Al(OH)2Cl, (CaOH)2CO3, double (KAl(SO4)2), complex (Ag[( NH3)2]Cl, K4).
Medium salts
Medium salts are salts that are the product of complete replacement of the hydrogen atoms of the corresponding acid with metal atoms or the NH4+ ion. For example:
H2CO3 ® (NH4)2CO3; H3PO4 ® Na3PO4
The name of the average salt is formed from the name of the anion followed by the name of the cation. For salts of oxygen-free acids, the name of the salt is made up of Latin name non-metal with the addition of a suffix –id, for example, NaCl - sodium chloride. If a non-metal exhibits a variable oxidation state, then after its name the oxidation state of the metal is indicated in parentheses in Roman numerals: FeS - iron (II) sulfide, Fe2S3 - iron (III) sulfide.
For salts of oxygen-containing acids, the ending is added to the Latin root of the element name –at for higher oxidation states, -it for lower ones. For example,
K2SiO3 – potassium silicate, KNO2 – potassium nitrite,
KNO3 – potassium nitrate, K3PO4 – potassium phosphate,
Fe2(SO4)3 – iron (III) sulfate, Na2SO3 – sodium sulfite.
For salts of some acids the prefix is used –hypo for lower oxidation states and –trans for high oxidation states. For example,
KClO – potassium hypochlorite, KClO2 – potassium chlorite,
KClO3 – potassium chlorate, KClO4 – potassium perchlorate.
Methods for obtaining medium salts:
Interaction of metals with non-metals, acids and salts:
2Na + Cl2 = 2NaCl
Zn + 2HCl = ZnCl2 + H2
Fe + CuSO4 = FeSO4 + Cu
Interaction of oxides:
basic with acids BaO + 2HNO3 = Ba(NO3)2 + H2O
acidic with alkali 2NaOH + SiO2 = Na2SiO3 + H2O
basic oxides with acidic Na2O + CO2 = Na2CO3
The interaction of acids with bases and with amphoteric hydroxides:
KOH + HCl = KCl + H2O
Cr(OH)3 + 3HNO3 = Cr(NO3)3 + 3H2O
The interaction of salts with acids, with alkalis and salts:
Na2CO3 + 2HCl = 2NaCl + CO2 + H2O
FeCl3 + 3KOH = 3KCl + Fe(OH)3¯
Na2SO4 + BaCl2 = BaSO4¯ + 2NaCl
Chemical properties medium salts:
Interaction with metals
Zn + Hg(NO3)2 = Zn(NO3)2 + Hg
Interaction with acids
AgNO3 + HCl = AgCl¯ + HNO3
Interaction with alkalis
CuSO4 + 2NaOH = Cu(OH)2¯ + Na2SO4
Interaction with salts
CaCl2 + Na2CO3 = CaCO3¯ + 2NaCl
Decomposition of salts
NH4Cl = NH3 + HCl
CaCO3 = CaO + CO2
(NH4)2Cr2O7 = N2 + Cr2O3 + 4H2O
Acid salts
Acid salts are products of incomplete replacement of hydrogen atoms in molecules of polybasic acids with metal atoms.
For example: H2CO3 ® NaHCO3
H3PO4 ® NaH2PO4 ® Na2HPO4
When naming an acidic salt, the prefix is added to the name of the corresponding average salt hydro-, which indicates the presence of hydrogen atoms in the acid residue.
For example, NaHS is sodium hydrogen sulfide, Na2HPO4 is sodium hydrogen phosphate, NaH2PO4 is sodium dihydrogen phosphate.
Acid salts can be obtained:
The action of excess polybasic acids on basic oxides, alkalis and medium salts:
K2O + 2H2S = 2KHS + H2O
NaOH + H2SO4 = NaHSO4 + H2O
K2SO4 + H2SO4 = 2KHSO4
By the action of excess acid oxides on alkali
NaOH + CO2 = NaHCO3
Chemical properties of acid salts:
Interaction with excess alkali
Ca(HCO3)2 + Ca(OH)2 = 2CaCO3 + 2H2O
Interaction with acids
Ca(HCO3)2 + 2HCl = CaCl2 + 2H2O + 2CO2
Decomposition
Ca(HCO3)2 = CaCO3 + CO2 + H2O
Basic salts
Basic salts are products of incomplete replacement of the hydroxo group in the molecules of polyacid bases with acidic residues.
Mg(OH)2 ® MgOHNO3
Fe(OH)3 ®Fe(OH)2Cl ® FeOHCl2
When naming the main salt, the prefix is added to the name of the corresponding middle salt hydroxo-, which indicates the presence of a hydroxo group. For example, CrOHCl2 is chromium (III) hydroxychloride, Cr(OH)2Cl is chromium (III) dihydroxychloride.
Basic salts can be obtained:
Incomplete neutralization of bases by acids
In order to answer the question of what salt is, you usually don’t have to think long. This chemical compound V everyday life occurs quite often. There is no need to talk about ordinary table salt. Detailed internal structure salts and their compounds are studied in inorganic chemistry.
Definition of salt
A clear answer to the question of what salt is can be found in the works of M.V. Lomonosov. He assigned this name to fragile bodies that can dissolve in water and do not ignite when exposed to high temperatures or open fire. Later, the definition was derived not from their physical, but from the chemical properties of these substances.
An example of a mixed acid is the calcium salt of hydrochloric and hypochlorous acid: CaOCl 2.
Nomenclature
Salts formed by metals with variable valence have an additional designation: after the formula, the valence is written in Roman numerals in parentheses. Thus, there is iron sulfate FeSO 4 (II) and Fe 2 (SO4) 3 (III). The name of a salt contains the prefix hydro- if it contains unsubstituted hydrogen atoms. For example, potassium hydrogen phosphate has the formula K 2 HPO 4 .
Properties of salts in electrolytes
The theory of electrolytic dissociation gives its own interpretation of chemical properties. In light of this theory, salt can be defined as a weak electrolyte which, when dissolved, dissociates (breaks apart) in water. Thus, a salt solution can be represented as a complex of positive negative ions, and the first are not hydrogen atoms H +, and the second are not atoms of the hydroxyl group OH -. There are no ions that are present in all types of salt solutions, so any general properties they don't have. The lower the charges of the ions that form the salt solution, the better they dissociate, the better the electrical conductivity of such a liquid mixture.
Solutions of acid salts
Acidic salts in solution break down into complex negative ions, which are the acid residue, and simple anions, which are positively charged metal particles.
For example, the dissolution reaction of sodium bicarbonate leads to the decomposition of the salt into sodium ions and the remainder HCO 3 -.
Complete formula looks like this: NaHCO 3 = Na + + HCO 3 -, HCO 3 - = H + + CO 3 2-.
Solutions of basic salts
Dissociation of basic salts leads to the formation of acid anions and complex cations consisting of metals and hydroxyl groups. These complex cations, in turn, are also capable of breaking down during dissociation. Therefore, in any solution of a salt of the main group, OH - ions are present. For example, the dissociation of hydroxomagnesium chloride proceeds as follows:
Spread of salts
What is salt? This element is one of the most common chemical compounds. Everyone knows table salt, chalk (calcium carbonate) and so on. Among carbonate acid salts, the most common is calcium carbonate. He is integral part marble, limestone, dolomite. Calcium carbonate is also the basis for the formation of pearls and corals. This chemical compound is an integral component for the formation of hard integument in insects and skeletons in chordates.
Table salt has been known to us since childhood. Doctors warn against consuming it in excess, but in moderation it is essential for exercise. life processes in the body. And it is needed to maintain the correct blood composition and the production of gastric juice. Saline solutions, an integral part of injections and droppers, are nothing more than a solution of table salt.
Salts - organic and inorganic chemicals complex composition. IN chemical theory There is no strict and definitive definition of salts. They can be described as compounds:
- consisting of anions and cations;
- obtained as a result of the interaction of acids and bases;
- consisting of acidic residues and metal ions.
Acidic residues can be associated not with metal atoms, but with ammonium ions (NH 4) +, phosphonium (PH 4) +, hydronium (H 3 O) + and some others.
Types of salts
Acidic, medium, basic. If all the hydrogen protons in an acid are replaced by metal ions, then such salts are called medium salts, for example, NaCl. If hydrogen is only partially replaced, then such salts are acidic, for example. KHSO 4 and NaH 2 PO 4. If the hydroxyl groups (OH) - bases are not completely replaced by an acidic residue, then the salt is basic, for example. CuCl(OH), Al(OH)SO4.
- Simple, double, mixed. Simple salts consist of one metal and one acid residue, for example, K 2 SO 4. Double salts contain two metals, for example KAl(SO 4) 2. Mixed salts have two acidic residues, e.g. AgClBr.
Organic and inorganic.
- Complex salts with a complex ion: K 2, Cl 2 and others.
- Crystal hydrates and crystal solvates.
- Crystalline hydrates with molecules of water of crystallization. CaSO 4 *2H 2 O.
- Crystal solvates with solvent molecules. For example, LiCl in liquid ammonia NH 3 gives LiCl*5NH 3 solvate.
- Oxygen-containing and oxygen-free.
- Internal, otherwise called bipolar ions.
Properties
Most salts are solids with a high melting point and do not conduct electricity. Solubility in water is an important characteristic; on its basis, reagents are divided into water-soluble, slightly soluble and insoluble. Many salts dissolve in organic solvents.
Salts react:
- with more active metals;
- with acids, bases, and other salts, if the interaction produces substances that do not participate in further reactions, for example, gas, insoluble precipitate, water. They decompose when heated and hydrolyze in water.
In nature, salts are widely distributed in the form of minerals, brines, and salt deposits. They are also extracted from sea water and mountain ores.
Salts are necessary to the human body. Iron salts are needed to replenish hemoglobin, calcium - participate in the formation of the skeleton, magnesium - regulate the activity of the gastrointestinal tract.
Application of salts
Salts are actively used in production, everyday life, agriculture, medicine, food industry, chemical synthesis and analysis, in laboratory practice. Here are just a few areas of their application:
- Sodium, potassium, calcium and ammonium nitrates (saltpeter); calcium phosphate, Potassium chloride is a raw material for the production of fertilizers.
- Sodium chloride is necessary for the production of table salt; it is used in the chemical industry for the production of chlorine, soda, and caustic soda.
- Sodium hypochlorite is a popular bleach and water disinfectant.
- Salts of acetic acid (acetates) are used in the food industry as preservatives (potassium and calcium acetate); in medicine for the manufacture of drugs, in the cosmetics industry (sodium acetate), for many other purposes.
- Potassium-aluminum and potassium-chromium alums are in demand in medicine and the food industry; for dyeing fabrics, leather, furs.
- Many salts are used as fixatives for determining chemical composition substances, water quality, acidity level, etc.
Our store offers a wide range of salts, both organic and inorganic.
What are salts?
Salts are complex substances that consist of metal atoms and acidic residues. In some cases, salts may contain hydrogen.
If we carefully examine this definition, we will notice that in their composition salts are somewhat similar to acids, the only difference being that acids consist of hydrogen atoms, and salts contain metal ions. It follows from this that salts are products of the replacement of hydrogen atoms in an acid with metal ions. So, for example, if we take the table salt NaCl, known to everyone, then it can be considered as a product of the replacement of hydrogen in hydrochloric acid HC1 with a sodium ion.
But there are also exceptions. Take, for example, ammonium salts; they contain acidic residues with an NH4+ particle, and not with metal atoms.
Types of salts
Now let's take a closer look at the classification of salts.
Classification:
Acid salts are those in which the hydrogen atoms in the acid are partially replaced by metal atoms. They can be obtained by neutralizing a base with excess acid.
Medium salts, or as they are also called normal salts, include those salts in which all hydrogen atoms in the acid molecules are replaced by metal atoms, for example, such as Na2CO3, KNO3, etc.
Basic salts include those in which the hydroxyl groups of bases are incompletely or partially replaced by acidic residues, such as Al(OH)SO4, Zn(OH)Cl, etc.
Double salts contain two different cations, which are obtained by crystallization from a mixed solution of salts with different cations, but the same anions.
But mixed salts include those that contain two different anions. There are also complex salts, which contain a complex cation or a complex anion.
Physical properties of salts
We already know that salts are solids, but you should know that they have different solubility in water.
If we consider salts from the point of view of solubility in water, they can be divided into groups such as:
Soluble (P),
- insoluble (N)
- sparingly soluble (M).
Nomenclature of salts
To determine the degree of solubility of salts, you can refer to the table of solubility of acids, bases and salts in water.
As a rule, all salt names consist of the names of an anion, which is presented in the nominative case, and a cation, which is in the genitive case.
For example: Na2SO4 - sodium sulfate (I.p.).
In addition, for metals, a variable oxidation state is indicated in parentheses.
Let's take for example:
FeSO4 - iron (II) sulfate.
You should also know that there is an international nomenclature for the name of the salts of each acid, depending on the Latin name of the element. For example, salts of sulfuric acid are called sulfates. For example, CaSO4 is called calcium sulfate. But salts are called chlorides hydrochloric acid. For example, NaCl, which is familiar to all of us, is called sodium chloride.
If they are salts of dibasic acids, then the particle “bi” or “hydro” is added to their name.
For example: Mg(HCl3)2 – will sound like magnesium bicarbonate or bicarbonate.
If in a tribasic acid one of the hydrogen atoms is replaced by a metal, then the prefix “dihydro” should also be added and we get:
NaH2PO4 – sodium dihydrogen phosphate.
Chemical properties of salts
Now let's move on to considering the chemical properties of salts. The fact is that they are determined by the properties of the cations and anions that are part of them.
The importance of salt for the human body
There have long been discussions in society about the dangers and benefits of salt that it has on the human body. But no matter what point of view opponents adhere to, you should know that table salt is a natural mineral substance that is vital for our body.
You should also know that with a chronic lack of sodium chloride in the body, death can occur. After all, if we remember our biology lessons, we know that the human body is seventy percent water. And thanks to salt, the processes of regulation and support occur water balance in our body. Therefore, it is impossible to exclude the use of salt under any circumstances. Of course, excessive consumption of salt will also not lead to anything good. And here the conclusion arises that everything should be in moderation, since its deficiency, as well as its excess, can lead to an imbalance in our diet.
Application of salts
Salts have found their application, as in production purposes, and in our daily life. Now let's take a closer look and find out where and what salts are most often used.
Salts of hydrochloric acid
The most commonly used salts of this type are sodium chloride and potassium chloride. The table salt that we eat is obtained from sea and lake water, as well as from salt mines. And if we eat sodium chloride, then in industry it is used to produce chlorine and soda. But potassium chloride is indispensable in agriculture. It is used as potassium fertilizer.
Sulfuric acid salts
As for sulfuric acid salts, they are widely used in medicine and construction. It is used to make gypsum.
Salts nitric acid
Salts of nitric acid, or nitrates as they are also called, are used in agriculture as fertilizers. The most significant among these salts are sodium nitrate, potassium nitrate, calcium nitrate and ammonium nitrate. They are also called saltpeter.
Orthophosphates
Among orthophosphates, one of the most important is calcium orthophosphate. This salt forms the basis of minerals such as phosphorites and apatites, which are necessary in the manufacture of phosphate fertilizers.
Carbonic acid salts
Carbonic acid salts or calcium carbonate can be found in nature in the form of chalk, limestone and marble. It is used to make lime. But potassium carbonate is used as a component of raw materials in the production of glass and soap.
Of course, you know a lot of interesting things about salt, but there are also facts that you would hardly have guessed.
You probably know the fact that in Rus' it was customary to greet guests with bread and salt, but you were angry that they even paid a tax for salt.
Do you know that there were times when salt was more valuable than gold? In ancient times, Roman soldiers were even paid in salt. And the most dear and important guests were presented with a handful of salt as a sign of respect.
Did you know that the concept of “wages” comes from English word salary.
It turns out that table salt can be used in medical purposes, since it is an excellent antiseptic and has wound-healing and bactericidal properties. After all, probably each of you has observed, while at sea, that wounds on the skin and calluses in salty sea water heal much faster.
Do you know why it is customary to sprinkle the paths with salt in winter when there is ice? It turns out that if salt is poured onto ice, the ice turns into water, since its crystallization temperature will decrease by 1-3 degrees.
Do you know how much salt a person consumes during the year? It turns out that in a year you and I eat about eight kilograms of salt.
It turns out that people living in hot countries need to consume four times more salt than those living in cold climates, because during the heat a large amount of sweat is released, and with it salts are removed from the body.
5.Nitrites, salts of nitrous acid HNO 2. Nitrites of alkali metals and ammonium are used primarily, and less - of alkaline earth and Zd metals, Pb and Ag. There is only fragmentary information about nitrites of other metals.Metal nitrites in the +2 oxidation state form crystal hydrates with one, two or four water molecules. Nitrites form double and triple salts, e.g. CsNO2. AgNO 2 or Ba(NO 2) 2. Ni(NO2)2. 2KNO 2, as well as complex compounds, for example Na 3.
Crystal structures known for only a few anhydrous nitrites. The NO2 anion has a nonlinear configuration; ONO angle 115°, H–O bond length 0.115 nm; the type of M-NO2 bond is ionic-covalent.
Nitrites K, Na, Ba are well soluble in water, nitrites Ag, Hg, Cu are poorly soluble. With increasing temperature, the solubility of nitrites increases. Almost all nitrites are poorly soluble in alcohols, ethers and low-polar solvents.
Nitrites are thermally unstable; Only nitrites of alkali metals melt without decomposition; nitrites of other metals decompose at 25-300 °C. The mechanism of nitrite decomposition is complex and includes a number of parallel-sequential reactions. The main gaseous decomposition products are NO, NO 2, N 2 and O 2, solid - metal oxide or elemental metal. The release of large amounts of gases causes the explosive decomposition of some nitrites, for example NH 4 NO 2, which decomposes into N 2 and H 2 O.
The characteristic features of nitrites are associated with their thermal instability and the ability of the nitrite ion to be both an oxidizing agent and a reducing agent, depending on the environment and the nature of the reagents. IN neutral environment nitrites are usually reduced to NO; in acidic conditions they are oxidized to nitrates. Oxygen and CO 2 do not interact with solid nitrites and their aqueous solutions. Nitrites contribute to the decomposition of nitrogen-containing organic matter, in particular amines, amides, etc. With organic halides RXH. react to form both nitrites RONO and nitro compounds RNO 2 .
The industrial production of nitrites is based on the absorption of nitrous gas (a mixture of NO + NO 2) with solutions of Na 2 CO 3 or NaOH with sequential crystallization of NaNO 2; Nitrites of other metals are obtained in industry and laboratories by the exchange reaction of metal salts with NaNO 2 or by the reduction of nitrates of these metals.
Nitrites are used for the synthesis of azo dyes, in the production of caprolactam, as oxidizing agents and reducing agents in the rubber, textile and metalworking industries, as food preservatives. Nitrites, such as NaNO 2 and KNO 2, are toxic, causing headaches, vomiting, depressing breathing, etc. When NaNO 2 is poisoned, methemoglobin is formed in the blood and red blood cell membranes are damaged. It is possible to form nitrosamines from NaNO 2 and amines directly in the gastrointestinal tract.
6.Sulfates, salts of sulfuric acid. Medium sulfates with the SO 4 2- anion are known, or hydrosulfates, with the HSO 4 - anion, basic, containing, along with the SO 4 2- anion, OH groups, for example Zn 2 (OH) 2 SO 4. There are also double sulfates containing two different cations. These include two large groups sulfates - alum, as well as shenites M 2 E (SO 4) 2. 6H 2 O, where M is a singly charged cation, E is Mg, Zn and other doubly charged cations. Triple sulfate K 2 SO 4 is known. MgSO4. 2CaSO4. 2H 2 O (polyhalite mineral), double basic sulfates, for example minerals of the alunite and jarosite groups M 2 SO 4. Al 2 (SO 4) 3 . 4Al(OH 3 and M 2 SO 4. Fe 2 (SO 4) 3. 4Fe(OH) 3, where M is a singly charged cation. Sulfates can be included in mixed salts, eg. 2Na2SO4. Na 2 CO 3 (burkeite mineral), MgSO 4 . KCl. 3H 2 O (kainite).
Sulfates are crystalline substances, medium and acidic in most cases, highly soluble in water. Sulfates of calcium, strontium, lead and some others are slightly soluble; BaSO 4 and RaSO 4 are practically insoluble. Basic sulfates are usually poorly soluble or practically insoluble, or are hydrolyzed by water. From aqueous solutions, sulfates can crystallize in the form of crystalline hydrates. Crystal hydrates of some heavy metals called vitriol; copper sulfateСuSO 4 . 5H 2 O, iron sulfate FeSO 4. 7H 2 O.
Average alkali metal sulfates are thermally stable, while acid sulfates decompose when heated, turning into pyrosulfates: 2KHSO 4 = H 2 O + K 2 S 2 O 7. Medium sulfates of other metals, as well as basic sulfates, when heated to sufficiently high temperatures, as a rule, decompose with the formation of metal oxides and the release of SO 3.
Sulfates are widely distributed in nature. They occur in the form of minerals, such as gypsum CaSO 4 . H 2 O, mirabilite Na 2 SO 4. 10H 2 O, and are also part of sea and river water.
Many sulfates can be obtained by the interaction of H 2 SO 4 with metals, their oxides and hydroxides, as well as the decomposition of volatile acid salts with sulfuric acid.
Inorganic sulfates are widely used. For example, ammonium sulfate is a nitrogen fertilizer, sodium sulfate is used in the glass, paper industries, viscose production, etc. Natural sulfate minerals are raw materials dm industrial production compounds of various metals, builds, materials, etc.
7.Sulfites, salts of sulfurous acid H 2 SO 3. There are medium sulfites with the SO 3 2- anion and acidic (hydrosulfites) with the HSO 3 - anion. Medium sulfites are crystalline substances. Ammonium and alkali metal sulfites are highly soluble in water; solubility (g in 100 g): (NH 4) 2 SO 3 40.0 (13 ° C), K 2 SO 3 106.7 (20 ° C). Hydrosulfites are formed in aqueous solutions. Sulfites of alkaline earth and some other metals are practically insoluble in water; solubility of MgSO 3 1 g in 100 g (40°C). Crystalline hydrates (NH 4) 2 SO 3 are known. H 2 O, Na 2 SO 3. 7H 2 O, K 2 SO 3. 2H 2 O, MgSO 3. 6H 2 O, etc.
Anhydrous sulfites, when heated without access to air in sealed vessels, are disproportionately divided into sulfides and sulfates; when heated in a current of N 2, they lose SO 2, and when heated in air, they are easily oxidized to sulfates. With SO 2 in aquatic environment medium sulfites form hydrosulfites. Sulfites are relatively strong reducing agents; they are oxidized in solutions with chlorine, bromine, H 2 O 2, etc. to sulfates. They decompose with strong acids (for example, HC1) with the release of SO 2.
Crystalline hydrosulfites are known for K, Rb, Cs, NH 4 +, they are unstable. The remaining hydrosulfites exist only in aqueous solutions. Density of NH 4 HSO 3 2.03 g/cm3; solubility in water (g in 100 g): NH 4 HSO 3 71.8 (0 ° C), KHSO 3 49 (20 ° C).
When crystalline hydrosulfites Na or K are heated or when the teeming pulp solution is saturated with SO 2 M 2 SO 3, pyrosulfites (obsolete - metabisulfites) M 2 S 2 O 5 are formed - salts of the unknown free pyrosulfuric acid H 2 S 2 O 5; crystals, unstable; density (g/cm3): Na 2 S 2 O 5 1.48, K 2 S 2 O 5 2.34; above ~ 160 °C they decompose with the release of SO 2; dissolve in water (with decomposition to HSO 3 -), solubility (g in 100 g): Na 2 S2O 5 64.4, K 2 S 2 O 5 44.7; form Na 2 S 2 O 5 hydrates. 7H 2 O and 3K 2 S 2 O 5. 2H 2 O; reducing agents.
Medium alkali metal sulfites are prepared by reacting an aqueous solution of M 2 CO 3 (or MOH) with SO 2, and MSO 3 by passing SO 2 through an aqueous suspension of MCO 3; They mainly use SO 2 from the exhaust gases of contact sulfuric acid production. Sulfites are used in bleaching, dyeing and printing of fabrics, fibers, leathers for grain conservation, green feed, feed industrial waste (NaHSO 3,Na 2 S 2 O 5). CaSO 3 and Ca(HSO 3) 2 are disinfectants in the winemaking and sugar industries. NaHSO 3, MgSO 3, NH 4 HSO 3 - components of sulfite liquor during pulping; (NH 4) 2SO 3 - SO 2 absorber; NaHSO 3 is an absorber of H 2 S from industrial waste gases, a reducing agent in the production of sulfur dyes. K 2 S 2 O 5 - a component of acidic fixatives in photography, an antioxidant, an antiseptic.