Ammonium bifluoride is a toxic inorganic compound of industrial production used in the glass, oil and metallurgical fields. The substance is often used as a substitute for hydrofluoric acid or hydrogen fluoride.
General Description and Physical Properties
Ammonium bifluoride most often has a solid state of aggregation and is presented in the form of crystals. The latter are characterized by high solubility in water, but zero in acetone and alcohol. The crystals have an orthorhombic syngony with a discrete group of motions P man. The substance decomposes at temperatures above 238 ° C.
This bifluoride does not have flammable and explosive properties.
Structure and chemical formula
The substance has several synonymous names, such as ammonium fluoride bifluoride , acid ammonium fluoride, ammonium hydrofluoride, etc. This compound has the chemical formula NH 4 (HF 2 ).
The chemical composition of the substance includes:
- ammonium cation (NH 4 + );
- bifluoride or hydrogen difluoride;
- anion (HF 2 - ).
A notable feature of this compound is the presence of the strongest hydrogen bond with a length of 114 microns. It combines fluorine and hydrogen in a centrosymmetric triatomic bifluoride anion. The energy of this bond exceeds 155 kJ / mol -1 .
In the crystalline form of the substance, four fluoride centers surround each ammonium cation, forming a tetrahedron.
Production form
Ammonium bifluoride is produced in two forms:
- solid (white crystals);
- in the form of a solution.
The solution is a clear liquid with a smell. The concentration of the starting material in such a mixture is from 28 to 30%.
Substance use
Ammonium bifluoride has a very wide range of applications. In particular, it is used for:
- glass processing;
- anodizing aluminum;
- as a substitute for more toxic and aggressive hydrofluoric acid, which improves environmental friendliness and reduces the cost of glass processing;
- cleaning metal surfaces;
- disinfection of thermal pipelines, leather and wood products;
- manganese casting (as flux);
- sand removal from oil wells;
- elimination of rust in boilers and pipes;
- flushing oil wires.
The replacement of hydrofluoric acid with ammonium hydrofluoride is used not only in glass processing, but also in well drilling.
Toxicity characterization
The hazard class of ammonium bifluoride is ADR 8. This substance is quite toxic to the human body with a strong corrosive effect. On contact with skin, this compound causes irritation, and on prolonged exposure burns. Ammonium bifluoride in the eyes can cause damage to the visual organ.
Inhalation of oxygen in conjunction with this substance causes the following symptoms:
- irritation of the mucous membranes of the nasopharynx and respiratory tract;
- nosebleeds;
- cough;
- wheezing
- dyspnea;
- nausea and vomiting.
The interaction of ammonium bifluoride with water leads to the formation of very dangerous hydrofluoric acid, which enhances the traumatic effect of this compound on contact with wet skin. In the case of a prolonged and intense exposure of a substance to the body, its effect leads to fluorine poisoning, stomach pain, weakness, seizures, and even death.
Regular human contact with ammonium bifluoride leads to the development of a pathological condition called fluorosis, in which fluoride is deposited in the bones and teeth.
Environmental friendliness
For the environment, this substance is less dangerous than for humans through direct contact. Ammonium bifluoride has a very important environmental quality - rapid decomposition (within a few days), which eliminates the possibility of its accumulation.
However, in a humid environment, this substance decomposes into hydrofluoric acid and ammonia, which are toxic to living organisms.