Ammonium nitrate

Chemical substance ammonium nitrate, formulawhich NH4NO3, for a long time known to chemists, as far back as 1659 it was discovered by IR Glauber. In the literature, one more name of this compound is widespread: ammonium nitrate. Externally, ammonium nitrate is a white crystal with high hygroscopicity. The boiling point of the compound is 235 ° C, and at 169.6 ° C the ammonium nitrate begins to melt. There are several crystalline modifications, which quite significantly affect the chemical, physical properties and spheres of its application.

For example, these differences are thatdifferent crystal modifications have a different kind of lattice. In total, there are five such modifications. For the first modification, the cubic form of the crystal lattice is characteristic, for the second and the fifth, tetragonal, for the third and fourth, the rhombic form. In this case, as a result of the transition of the connection from one modification to another, a gradual but steady increase in the volume of the unit cell is observed. This property determines the difference in chemical properties. Thus, for example, modification IV has a density of 1.725 g / cm3, the melting point is already 139.4 ° C.

The solubility of ammonium nitrate is as follows: in one hundred grams of water at a temperature of 0 ° C dissolves 119 grams of substance, at a temperature of 25 ° C already 212 grams are dissolved, and at 50 ° C - 346 grams of ammonium nitrate. In addition, ammonium nitrate can dissolve in pyridine, methanol and ethanol. A very important characteristic of the compound is that when the impact is applied or if the ambient temperature is over 270 ° C, ammonium nitrate decomposes, causing an explosive effect.

By means of indicators it is possible to define acidicmedium, which includes ammonium nitrate, hydrolysis with its participation is a reaction, the equation of which can be written as: NH4NO3 + H2O = NH4OH + HNO3. Ammonium nitrate reacts with alkaline solutions. As a result of such reactions, ammonia is formed, and the reaction process itself acts as a qualitative reaction to ammonium nitrate.

As a rule, the substance is produced by carrying outneutralization reaction with 60% HNO3. As a neutralizing agent NH3 is used in the gaseous state. The process generates heat, which is sent to evaporate the solution of ammonium nitrate and the preparation of the substance in the form of granules.

The most common use of nitrateammonium was obtained in agriculture, as a valuable nitrogen fertilizer. The compound is actively used in the manufacture of explosives, and as a reagent - as a zirconium solvent in fuel elements, during nuclear waste recovery operations. Physicochemical properties cause a constant increase in demand in the substance, so its production is steadily increasing and today it reaches 20 million tons per year, when the substance is recalculated into nitrogen.

Ammonium nitrate can be obtained in laboratoryconditions with the strictest precautions and safety rules. For this purpose, a mixture of strongly dilute nitric acid and ammonia is produced in an ice bath (aqueous ammonia solution). To conduct such a reaction is best remotely, for example, using manipulators, and being at a sufficiently safe distance from the location of the mixed solution. Carrying out the reaction consists in the constant mixing of the acid in the ammonia solution during periodic verification by the indicator (litmus test) of reaching the neutral reaction state. In the same way, control over the course of the reaction is also ensured. If the acid medium is exceeded, an alkaline component is added to the solution, and vice versa.