Nitrogen fertilizers. Ammonium nitrate

Ammonium nitrate is a part of the most important group of nitrogen fertilizers. Nitrogen performs an exceptional role in the life of plants. This substance is included in the composition of chlorophyll, which is the acceptor of protein and solar energy, which is necessary for building a living cell.

Plants can consume only bound nitrogen in the form of amides, ammonium salts, nitrates. A relatively small amount of material is formed due to the functioning of soil microorganisms. It should be noted that modern agriculture can not exist without additional fertilization of the nitrogen group into the soil, which are obtained in the process of industrial binding of atmospheric nitrogen. Mixtures falling into this category differ from each other in form of connection, phase state (liquid or solid). There are also physiologically alkaline and acidic fertilizers.

Ammonium nitrate, the formula of which is NH ₄ NO ₃ , is a white crystalline substance that contains thirty-five percent of nitrogen in nitrate and ammonium form. Both these forms are easy to assimilate plants. Granulated ammonium nitrate is used in large volumes before sowing and as a feeding. In a smaller amount, it is used in the manufacture of explosives.

Ammonium nitrate is of different types. Types A and B, for example, are used for industrial purposes, in explosive mixtures (ammonals, ammonites).

Ammonia and nitric acid are used for fertilizer production . The molecular weight of the obtained substance is 80.043 amu. Pure ammonium nitrate contains sixty percent of oxygen, five percent of hydrogen and thirty-five percent of nitrogen (in the technical product, nitrogen is at least thirty-four percent).

Depending on the temperature, there are five crystalline modifications of the substance. All of them are thermodynamically stable at atmospheric pressure. For each modification, a certain temperature range and a polymorphic transition assume a change in the crystal structure, absorption or release of heat, abrupt changes in the specific volume, entropy, heat capacity, and so on. Such transformations are considered enantiotropic - reversible.

Ammonium nitrate is an oxidizer and is capable of supporting combustion. In the case where the products of thermal decomposition are not able to be freely removed, the substance can detonate (explode) under certain conditions.

When exposed to an elevated temperature (two hundred and ten to two hundred and twenty degrees), ammonia accumulates in a confined space, the concentration of nitric acid decreases. In this connection, a significant decrease in the decomposition reaction is noted. The thermal decomposition hardly stops. When an even higher temperature is applied, a more rapid oxidation of ammonia takes place, the reaction of the accumulating substance begins to flow with considerable acceleration. It can also provoke an explosion.