Nh4 2so4 decomposition when heated. Ammonium sulfate. Behavior in soil

Chemical formula: (NH 4) 2 SO 4.

In industry, ammonium sulfate is obtained in the form of crystals by the reaction of ammonia and sulfuric acid, either directly or by oximation of cyclohexanone and neutralization of sulfate ester and free sulfuric acid with ammonia, as a result of the Beckmann rearrangement in the production of caprolactam.
Ammonium sulfate is also a product of ammonia capture by sulfuric acid during coal coking, in the metallurgical industry, and in the production of caprolactam. According to the production process, coke sulfate and metallurgical ammonium sulfate have significant impurities of compounds, even heavy metals.

Application of ammonium sulfate.

Agriculture.
Ammonium sulfate is one of the nitrogen-sulfur mineral fertilizers widely used in agriculture; it contains 21% nitrogen in ammonium form and 24% sulfur. Its hygroscopicity is weak, so during long-term storage it does not cake and retains its flowability. Provides a significant increase in the yield of tea, rye, potatoes, cotton, rice, oats, sugar beets. Competes successfully with the best nitrogen fertilizers. Ammonium sulfate, thanks to the ammonium form of nitrogen, compatible with sulfur, prevents the accumulation of nitrates by 3 times, reduces the content of radionuclides in plants by 2 times. Can be used in contaminated areas.

It is used for all agricultural crops (from potatoes to citrus fruits) on black and gray soils. The fertilizer has a valuable quality - low migration ability, since the ammonium cation is actively absorbed by the soil and this protects it from being washed out. Therefore, ammonium sulfate is recommended to be applied on light soils, during irrigation, i.e. where there is a potential danger of loss of fertilizer nitrogen due to migration phenomena. Ammonium nitrogen from ammonium sulfate is absorbed by plants. Sulfur is necessary for the nutrition of all crops, as it is part of some essential amino acids synthesized by plants.

In biochemistry, reprecipitation with ammonium sulfate is a common method for protein purification.
In the food industry, emulsifier E517 is registered as a food additive.
In fire extinguishing agents, ammonium sulfate is used as a fire retardant.
It is used in the technology of water chlorination with ammoniation, it is introduced into the treated water a few seconds before chlorine, with chlorine it forms chloramines - binding free chlorine, due to which the formation of organochlorines harmful to the human body is significantly reduced, the consumption of chlorine is reduced, and the corrosion of water pipes is reduced.
In the mining industry, ammonium sulfate is introduced into the composition of the explosive as a gel-forming component during the preventive treatment of goafs to reduce flammability and eliminate the danger of spontaneous ignition.

Ammonium sulfate is also used for the production of:
- herbicides;
- animal feed;
- leather dressing;
- construction insulation.

Safety requirements for ammonium sulfate (ammonium sulfate) GOST 9097-82.
Ammonium sulfate is a non-flammable substance. When heated to 235° C, it can decompose, releasing ammonia and sulfur trioxide. To protect against dust, use a dust respirator and canvas gloves.

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Physical and chemical properties

Ammonium sulfate (NH 4) 2 SO 4 - colorless crystals, density - 1.766 g/cm 3. At temperatures above +100°C it decomposes with the release of ammonia NH 3 and the formation first of NH 4 HSO 4, and subsequently (NH 4) 2 S 2 O 7 and sulfanilic acid.

Solubility in water: at 0°C - 70.5 g/100 g, at +25°C - 76.4 g/100 g, at +100°C - 101.7 g/100 g. Oxidizes to N 2 under by the action of strong oxidizing agents, for example, potassium permanganate KMnO 4.

Ammonium sulfate contains:

• nitrogen by mass fraction in terms of dry matter - not less than 21%;
• water - 0.2%;
• sulfuric acid - no more than 0.03%.

Fractional composition of the fertilizer:

• mass fraction of fractions larger than 0.5 mm - no less than 80%;
• less than 6 mm - 100%.

Friability - 100%.

The mass fraction of the residue insoluble in water does not exceed 0.02%.

Application

Agriculture

Ammonium sulfate in agriculture is used as the main fertilizer for various crops.

Industry

Ammonium sulfate in the chemical industry is used as a component of the precipitation bath in the formation of viscose fiber. In the glass industry - as an additive to glass batch to improve its fusibility.

Behavior in soil

When applied to the soil, ammonium sulfate quickly dissolves, and a significant part of the NH 4 + cations enters the soil-absorbing complex. At the same time, an equivalent amount of displaced cations passes into the soil solution. In this case, the ammonium ion loses its mobility. This eliminates the risk of it being washed out during soil leaching.

Being in an exchange-absorbed state, ammonium ions are well absorbed by plants. (Image)

Due to nitrification, ammonium nitrogen turns into nitrate form. The rate of transition of ammonia nitrogen into nitrate nitrogen depends on the conditions necessary for nitrification: temperature, aeration, humidity, biological activity and soil reaction. One of the main factors influencing the rate of nitrification is the degree of soil cultivation.

Waterlogging and increased soil acidity inhibit nitrification. Liming acidic soils significantly speeds up this process. After ammonium nitrogen is converted into nitrate nitrogen, it acquires all the properties of nitrate fertilizers. As a result of the nitrification process, nitric acid is formed in the soil and sulfuric acid is released.

(NH 4) 2 SO 4 + 4O 2 → 2HNO 3 + H 2 SO 4 + 2H 2 O

In the soil, these acids are neutralized by interacting with bicarbonates of the soil solution and cations of the soil absorption complex.

Neutralization of mineral acids is accompanied by the use of bicarbonates of the soil solution and the displacement of bases from the PPC by hydrogen. This weakens the buffering capacity of soils and increases their acidity.

A single application of ammonium sulfate may not affect the soil reaction. With the systematic use of this fertilizer, the soil environment can become significantly acidic. The degree of acidification increases with lower buffer capacity of soils.

Application on various types of soils

When used for a long time, ammonium sulfate has an oxidizing effect on the soil.

On acidic soils

On black soils

On chestnut soils

On light soils

Methods of application

Ammonium sulfate is most suitable for. But it is also acceptable to use for surface winter grain crops, hayfields and pastures, as well as

DEFINITION

Ammonium sulfate is a white substance (Fig. 1), the crystals of which decompose when heated.

It is highly soluble in water (hydrolyzes into the cation). Does not form crystalline hydrates.

Rice. 1. Ammonium sulfate. Appearance.

Table 1. Physical properties of ammonium sulfate.

Preparation of ammonium sulfate

There are industrial and laboratory methods for producing ammonium sulfate. In the first case, the reaction of neutralizing sulfuric acid with synthetic ammonia is used. In addition, flue gases from power plants and sulfuric acid production are used as raw materials for the production of this substance.

The main laboratory method for producing ammonium sulfate is the reaction between concentrated sulfuric acid and ammonia:

H 2 SO 4 + 2NH 3 = (NH 4) 2 SO 4.

Chemical properties of ammonium sulfate

Ammonium sulfate is a medium salt formed by a weak base - ammonium hydroxide (NH 4 OH) and a strong acid - sulfuric acid (H 2 SO 4). It hydrolyzes into the cation. The nature of the aqueous solution of ammonia sulfate is acidic. The hydrolysis equation will look like this:

(NH 4) 2 SO 4 ↔ 2NH 4 + + SO 4 2-;

NH 4 + + SO 4 2- + HOH ↔ NH 4 OH + SO 4 2- + H +;

(NH 4) 2 SO 4 + 2HOH ↔ 2NH 4 OH + H 2 SO 4.

Ammonium sulfate enters into exchange reactions with acids, alkalis and other salts:

(NH 4) 2 SO 4 + H 2 SO 4 (conc) = 2NH 4 HSO 4;

(NH 4) 2 SO 4 + 2NaOH conc = Na 2 SO 4 + 2NH 3 + 2H 2 O;

(NH 4) 2 SO 4 + BaCl 2 = BaSO 4 ↓ + 2NH 4 Cl.

Ammonium sulfate is oxidized by potassium permanganate and potassium dichromate:

(NH 4) 2 SO 4 + 2KMnO 4 = 2MnO 2 ↓ + N 2 + 4H 2 O;

(NH 4) 2 SO 4 + K 2 Cr 2 O 7 = N 2 + Cr 2 O 3 + K 2 SO 4 + 4H 2 O (t = 250 - 350 o C).

When heated to a temperature of 235 - 357 o C, ammonium sulfate decomposes into ammonium hydrogen sulfate and ammonia:

(NH 4) 2 SO 4 = NH 4 HSO 4 + NH 3.

Application of ammonium sulfate

Ammonium sulfate has found wide application in various industries, such as the production of mineral fertilizers, textiles (viscose fiber), powder fire extinguishers, as well as in the food industry (additive E517) and biochemistry.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2