Mercury Oxide

Let us know about the Mercury Oxide. Mercury oxide (I), whose chemical formula is represented as Hg 2 or, it is a compound in the solid phase, which is considered toxic and unstable from a chemical point of view, it turns into mercury in its initial form and Oxide (II).

Mercury Oxide

There are only two chemical species that can form mercury when combined with oxygen, as this metal has two unique oxidation states (Hg). + and Hg 2+ ): mercury oxide (I) and mercury oxide (II). The mercury oxide (II) solid is in a state of aggregation, which obtains in two relatively stable crystalline forms.

This compound is also known simply as mercury oxide, so only this species will be treated hereafter. A very common reaction that occurs with this substance is that, when subjected to heating, decomposition occurs, producing mercury and gaseous oxygen in an endothermic process.

chemical composition

Under atmospheric pressure conditions, this species occurs in two unique crystalline forms: one known as cinnabar and the other known as montrodita, which is rarely found. Both forms become tetragonal above 10 GPa of pressure.

The cinnabar structure is based on primitive hexagonal cells (hP6) with sacral symmetry, with the helical axis oriented to the left (P3) 2 21); Instead, the structure of the monodite is orthorhombic, based on a primitive grid that slides planes perpendicular to the three axes (Pnma).

In contrast, the two forms of mercury oxide can be distinguished visually, as one is red and the other yellow. This difference in color occurs thanks to the dimensions of the particle, since the two forms have the same composition.

To produce the red form of mercury oxide, the heating of metallic mercury to a temperature around 350 °C, or in the presence of oxygen in the pyrolysis process of mercury (II) nitrate (Hg(NO)) can be resorted to. 3 ) 2 ).

In the same way, precipitation of Hg ion can be resorted to to produce the yellow form of this oxide 2+ with the base aqueous form.


– It has a melting point of about 500 ° C (equivalent to 773 K), above which it undergoes decomposition, and a molar mass or molecular weight of 216.59 g / mol.

– It is in a state of solid aggregation in various colors: orange, red or yellow, according to the degree of dispersion.

– It is an oxide of inorganic nature, the ratio of which with oxygen is 1: 1, which makes it a binary species.

It is considered to be insoluble in ammonia, acetone, ether and alcohol as well as other solvents of organic nature.

– Its solubility in water is very low, being about 0.0053 g/100ml at standard temperature (about 25 °C) and with increasing temperature.

– It is considered soluble in most acids; However, the yellow form indicates greater reactivity and greater solubility.

When mercury oxide is exposed to air it undergoes decomposition, while its red form is exposed to light sources.

– When subjected to heating of the temperature at which it decomposes, it releases mercury gases of high toxicity.

Mercury can be combined with oxygen at a cost-effective rate only when heated to 300-350 °C.


It is used as a precursor in obtaining elemental mercury, as it undergoes decomposition processes quite readily; In turn, when it decomposes it produces oxygen in its gaseous form.

Similarly, this oxide of inorganic nature is used as a standard type of titrant or titrant agent for ionic species, since a compound that has a greater stability than its initial form is produced.

In this sense, mercury oxide undergoes dissolution when it is found in a concentrated solution of the parent species, producing a compound called hydroxylposose.

These compounds are complexed with the structure M X (OH) and , where M represents a metal atom and the subshells x and y represent the number of substituents found in the molecule of that species. They are very useful in chemical investigations.

In addition, mercury(II) oxide can be used in laboratories to produce various metal salts; For example, mercury acetate (II), which is used in organic synthesis processes.

This compound is used, when mixed with graphite, as a material for cathodic electrodes in mercury batteries and the production of mercury oxide and zinc electric cells.


– This substance, which very weakly manifests basic characteristics, is a very useful reagent for various applications such as those mentioned earlier, but at the same time it poses a significant risk to human beings when exposed to this Presents..

Mercury oxide has a high toxicity, being able to be absorbed through the respiratory tract as it releases irritating gases as an aerosol, in addition to being extremely toxic if it is exposed to direct contact through the skin. is absorbed or if it is absorbed with it.

This compound causes irritation to the eyes and can cause damage to the kidneys resulting in kidney failure.

– When consumed in one way or another by aquatic species, this chemical substance bioaccumulates in them and affects the bodies of humans who regularly consume them.

– the heating of mercury oxide produces mercury vapor that has high toxicity in addition to gaseous oxygen, thus increasing the risk of flammability; That is, to produce fire and improve combustion in them.

This inorganic oxide has a powerful oxidizing behavior, for which it reacts violently when exposed to reducing agents and certain chemical substances such as sulfur chloride (Cl). 2 S 2 ), hydrogen peroxide (H 2 O 2 ), chlorine and magnesium (only when heated).