Some facts about mercury, or another way to apply potassium permanganate
Main properties of mercury and potassium permanganate
Mercury has been known to humanity from ancient times. Alchemists who strove to discover the philosopher’s stone believed that liquid mercury was the main component of all metals, and could turn into gold.
Mercury is the 80th element in the periodic table, and in nature this substance is quite rare, but it is impossible to imagine modern life without it. Mercury is actively used in metallurgy, and in chemistry it is used to make amalgams of metals and conduct various experiments. It also plays a vital role in medicine: remember the ordinary thermometer, which contains mercury.
In industry, mercury is obtained by the same method that was used in the past, which involves the firing of cinnabar, i.e. bivalent mercury sulfide HgS, a reddish-brown mineral. During firing, mercury vapor accumulates, which is then collected.
HgS + O₂ ⟶ Hg + SO₂↑
There is also a metallothermic method of obtaining mercury:
HgS + Fe ⟶ FeS↓ + Hg
Physical properties of mercury
Mercury is the only chemical element of its kind which is a liquid metal of a whitish-silvery color under standard conditions. Hg melts at a temperature of -38.83 degrees Celsius, and starts to boil at 356.73 °C.
With metals, mercury may form alloys – amalgams. But it does not form amalgams with some metals, including iron. For this reason, mercury can be transported in steel containers.
Mercury displays a relatively low chemical activity. The only thing that can dissolve this metal is aqua regia, a mixture of concentrated acids, hydrochloric and nitric, and also nitric acid (diluted or concentrated) and sulfuric acid. The metal is also quite stable in air and does not mix with water.
Hg + 4HNO₃ (concentrated) ⟶ Hg(NO₃)₂ + 2NO₂ + 2H₂O,
6Hg + 8HNO₃ (diluted.) ⟶ 3Hg₂(NO₃)₂ + 2NO + 4H₂O,
Hg + 2H₂SO₄ ⟶ HgSO₄ + SO₂ + 2H₂O.
Chemical properties of mercury
Mercury also interacts with non-metals: for example, at a temperature of over 300 degrees Celsius, it reacts with oxygen with the formation of mercury(II) oxide:
2Hg + O₂ ⟶ 2HgO.
On heating, mercury actively reacts with sulfur, and as a result of the chemical reaction mercury (II) sulfide forms.
Hg + S ⟶ HgS.
Mercury can enter into a reaction with halogens, for example with the greenish-yellow gas chlorine:
Hg + Cl₂ ⟶ HgCl₂.
Interaction with acids
In the electrochemical series, mercury comes after hydrogen: it does not interact with water, alkalis or non-oxidizing acids.
Toxicology of mercury
Everyone remembers that it’s very dangerous to break a thermometer containing mercury. Even school textbooks tell you what to do in this situation. Indeed, even in small amounts the silvery-white metal can be harmful to human health.
But mercury can be neutralized with potassium permanganate, or as it is popularly known, manganese crystals – purple-black crystals which dissolve well in water.
Here you’ll find easy and entertaining experiments with KMnO₄.
Removal of mercury is called demercuration, and potassium permanganate is used in tandem with other substances, for example, the “affected area” is rinsed with a solution of manganese crystals, and then with iodine.