Mercury (mercuric chloride) chloride: preparation, properties and application

It's no secret that mercury compounds are very toxic and toxic. In the US, they are banned for use in most cosmetic products, and in Canada are included in the list of the most dangerous substances. At the same time, they are widely used in the chemical industry for the manufacture of paints, fungicides, plastics, as well as in medicine and engineering. One of the representatives of this class of substances is mercuric chloride (II), which is better known under its second name - sulema. Let's consider this connection in more detail.

Formula and properties

Mercuric chloride 2-valent is designated HgCl ₂ . This compound is a white crystalline powder. At a temperature of 277 ° C it begins to melt, and at 304 ° C it boils. Under normal conditions (25 ° C), its density is 5.43 g / cm ³ . Mercury chloride is easily chalked up, differs appreciably volatility. The solubility of mercury in water depends largely on its temperature. Thus, at 20 ° C this figure is only 6.6%, but it is worthwhile to bring the water to a boil (100 ° C) and it reaches 58.3%. In addition, mercury chloride is able to dissolve in ether, acids, pyridine; In the NaCl solution, this process is accompanied by the formation of complex compounds. As the electrolyte HgCl _{2 is} rather weak. In daylight, especially when exposed to organic compounds, this substance is easily reduced to monovalent chloride Hg ₂ Cl ₂ (calomel) and metallic mercury.

Receiving

In large quantities, mercury (II) chloride is currently produced only through direct synthesis from mercury and chlorine. The second way to obtain the mercury is to dissolve HgO in concentrated hydrochloric acid (HCl). In practice, it is used less often, mainly in the course of laboratory experiments. In the first case, mercury is heated in a chlorine atmosphere to a very high temperature (about 340 ° C), after which it ignites and burns to form a bluish white flame. The resulting vapors thicken as they cool down and, depending on the preparation technology, form a fine powder or solid pieces.

Application

It should be noted that mercury chloride was the first substance based on Hg, which was used as an antiseptic and disinfectant. In this respect, mercuric chloride is highly effective, but at the same time very toxic. It is able to be absorbed through the skin and mucous membranes and accumulate in the human body. Before, when people did not yet know about the dangers of mercury chloride, they used it to cure skin diseases. Now in medicine it is used more for the disinfection of clothes, linen, items of nursing, etc. Since this substance is very poisonous, its solutions are often specially colored so that it is not mistakenly mixed with other medicines.

In industry, mercury chloride is used in electroforming, for preserving wood, for thermal metallization and bronzing. Sulema is used for the manufacture of batteries, paints for the underwater part of hulls of sea vessels. It is used for tanning leather, in lithography, photography, as an insecticide, etc.