Ammonia solution - preparation and application
Nitrogen (nitrogen) has several compounds withHydrogen (hydrogen), of which ammonia is the most important. Under laboratory conditions, it is obtained by heating a mixture of ammonium chloride with potassium hydroxide. Until the end of the 19th century, the Chilean deposit of sodium nitrate was considered the only source of Nitrogen compounds. Thanks to scientific developments, chemists, several methods of fixing the atmospheric nitrogen have been proposed. The first of these was the cyanamide method of ammonia synthesis. This method is based on the property of nitrogen to combine with calcium carbamide. For this, nitrogen is passed through heated calcium carbide:
N2 + CaC2 = CaCN2 + C
The CaCN2 (calcium cyanide) thus obtained is used as a nitrate fertilizer in agriculture. It should be noted that the treatment of this compound with water vapor produces ammonia:
CaCN2 + 3H20 = 2NH3 + CaCO3
Ammonia is processed into nitrate acid and nitrogen fertilizers. In modern chemistry, another method of obtaining NH3 is widespread: its synthesis from Nitrogen and Hydrogen:
1/2 N +3/2 H2 = NH3
The ammonia obtained in this way is called synthetic. Industrial synthesis of ammonia is produced in the presence of a catalyst and at a temperature of 500 degrees.
Ammonia is a gas that has a sharp characteristicsmell, it is lighter than air. Do not inhale NH3 for a long time, as it is toxic. This gas dissolves fairly well in H2O. The concentrated aqueous ammonia solution contains 25% NH3.
When cooled (to -79 ° C), an aqueous solution of ammoniapasses into crystalline hydrate. Scientific studies have shown that the bulk of NH3 in the aqueous solution resides in the form of hydrated molecules (NH3 · nH2O) and only a small part of the dissolved ammonia (about 0.5%) interacts with water:
NH3 + H2O = NH4 + + OH -
Alkaline reaction of ammonia solutions is due topresence of hydroxide ions. Traditionally, ammonia solution is designated as NH4OH. The alkalinity of the solution is due to the presence of a hydroxyl group, which is formed as a result of the dissociation of ammonium hydroxide.
A solution of ammonia is considered a weak base. In laboratories, ammonia is sometimes obtained by heating ammonia. Ammonia is a fairly active chemical compound, interacts with many substances, but exhibits only reducing properties.
Ammonia burns, in the presence of Oxygengreenish-yellow flame, while oxidizing to free Nitrogen. In the presence of a catalyst (platinum), the oxidation of ammonia passes further to the formation of nitro- gen oxide. This reaction is used in the process of nitrate production. It should be said that most of the ammonia thus obtained is spent on the production of nitrate fertilizers, as well as nitrate acid.
During evaporation at -33.4 ° C, liquid NH3 fromThe environment absorbs a lot of heat, causes cooling. This property is used in refrigeration plants to produce artificial ice when storing perishable food. Not infrequently liquid ammonia is used in the construction of underground structures. The ammonia solution is used in laboratory practice, in the chemical industry, in household applications, and in medicine.
Ammonia solution application. Applied as a means to stimulate respiration and remove the patient from an unconscious state. Large concentrations of NH3 can cause respiratory arrest. Sometimes an ammonia solution is used as an emeticmeans (10 drops per 100 ml of water). It should be taken into account that this pharmaceutical agent can not be applied externally in the presence of skin diseases (eczema, dermatitis). When poisoning with ammonia vapor, physicians prescribe acetate, citrate, tartrate (tartaric acid) in 1% concentration. In surgical practice, a solution of ammonia (25 ml / 5 l of boiled, warm water) is used.
