The manganese oxide (MnO 2) is an inorganic chemical compound consisting of manganese element with a +4 oxidation number and oxygen in oxide formation has an oxidation number of -2. It is also known by the names of manganese (IV) oxide and manganous anhydride.
It is a dark brown to black solid. It is found in nature as the mineral pyrolusite, black in color and which crystallizes forming dendrites (branched elongations). It can be obtained as a black residue in the reaction between ethylene and potassium permanganate after the formation of glycol by the oxidizing action of potassium permanganate.
It is very important in the glass industry due to its character as an oxidizing agent, since it eliminates the green color from ferrous compounds and turns them into ferric.
Chemical structure
The chemical structure of the compound corresponds to that of an anhydride and not that of a basic oxide, as would be expected since it is made up of a metal and a non-metal.
This special case is due to the behavior assumed by manganese in the different oxidation states it possesses. Thus, for oxidation states +2 and +3 it forms the oxides MnO and Mn 2 O 3 respectively, which when reacting with water form the manganous hydroxides and manganic hydroxide, respectively.
However, Mn 2 O 3 in a slightly acidic medium behaves like an anhydride. With the oxidation states +4, +6 and +7, MnO 2, MnO 3 and MnO 4 form acids when reacting with water.
In a slightly acidic medium, MnO 2 behaves like a basic oxide, so it could form the corresponding hydroxide.
It should be borne in mind that in this case we are not talking about amphoteric properties, according to which a compound can behave like an acid or a base. This is a special case of Mn behavior.
Properties
Applications
- Used as a source of manganese
- As an oxidant in alkaline batteries
- Paints for glass, ceramics and porcelain.
- In obtaining chlorine and iodine.
- In the decomposition of hydrogen peroxide for the formation of gaseous oxygen and water.
- In the decomposition reaction of potassium chlorate for the production of gaseous oxygen and potassium chloride.
- Dissolved in acetone or dichloromethane, it oxidizes primary alcohols to aldehydes and secondary alcohols to ketones.
- Manufacture of alkaline batteries.
As a catalyst
This applies in oxidation-reduction reactions, for the removal of sulfides such as H 2 S and cations such as Fe +2 and Mn +2, arsenic and radium that are found in groundwater that present contamination by this type of compound.
This contamination can be generated either by uncontrolled spills of toxic materials, by washing contaminated soils or by the presence of chemical elements at the time of water extraction.
The high purity MnO 2 obtained from pyrolusite used as a filter (Filox) is the most effective means of removing this kind of impurities from groundwater.
Health effects
- Avoid contact with skin.
- In case of contact, wash the corresponding area.
- Do not inhale the powders.
- On eye contact irritation and redness are observed. Wash with plenty of water, let the water run through the eyes and seek medical assistance in case of seriousness.
- In contact with the skin irritation and redness are observed. Wash the affected area with plenty of soap and water.
- Prolonged contact with the skin removes its natural fat, triggering a dermatitis.
- By inhalation it can cause a flu-like illness (metallic fumes). The condition is characterized by high fever, chills, dry mouth and throat, muscle pain, and headache.
- May irritate the respiratory tract and increase the incidence of respiratory infections (pneumonia). Poisoning from absorption of inorganic manganese salts through the lungs is unlikely, but chronic poisoning can occur.
- Chronic exposure to manganese dioxide dust or smoke over a long period of time can affect the central nervous system and lead to the development of Parkinson's-like disease, walking difficulties, muscle spasms and behavior changes.
- By ingestion it can cause abdominal pain and nausea.
- It is not flammable, but helps spread fire in incandescent materials. If heated above 535 ° C the substance decomposes to manganese (III) oxide Mn 2 O 3 and oxygen, which is flammable and increases the fire hazard. In this case, the fire must be extinguished with foam or carbon dioxide.
- In case of spillage, do not handle the compound without proper personal protection.
- Store the compound in well-closed containers, in a cool, dry place and away from incompatible substances such as organic material and combustible material.
- The storage location should be dry and have acid corrosion resistant floors with good drainage.
- Personal protection material should be used, such as gloves, safety glasses, filter masks against vapors, dust and smoke.
References
- B, (2015), Manganese Dioxide, The Royal Society of Chemistry - Chemistry world, retrieved from chemistryworld.com
- Karal, (2014), Mangnese Dioxide, Safety Data Sheet, Recovered from, karal.com.mx
- Your virtual teacher. (2015-02-25). Inorganic Manganese Compounds (Special Case 1) - Theory Lesson), retrieved from, youtube.com
- Ecured, (nd), Manganese Dioxide, Recovered from ecured.cu
- Angarita G, Johnny., (2017), Manganese Dioxide: An Exceptional Technology. Hidroteco, recovered from hydrotecocr.com
- Fernández, G., (2015), Manganese Dioxide MnO 2 / acetone, Organic Chemistry, Recovered from quimicaorganica.net
- Tronox, (2011), Manganese Dioxide, Safety Data Sheet, Recovered from, tronox.com