Hello, everyone!
In this video I want to tell you about such a metal as manganese.
In the periodic table of chemical elements,
manganese is located in the 7th group
in the period of so-called "transition metals."
In nature, manganese is present in the
composition of minerals pyrolusite
and in manganese dioxide and braunite.
Metallic manganese that is derived from these minerals
does not particularly look like a metal.
All because of the lead of manganese dioxide
covering the metal pieces.
Pure manganese is quite fragile, and breaks easily
with little effort.
When heating a piece of manganese,
at first, it gets active and oxidized in the air
as evidenced by the iridescent layer of oxide film.
True, over time, the oxide layer becomes
sufficiently thick and dense to protect the metal from
further oxidation.
This process is called preservation.
By the way, in this shot you can see how well the metal
expands when heated.
The metal manganese reacts well with acid.
[Added?] with sulfuric acid, it forms hydrogen and manganese sulfate.
which has a light pink color.
In its solid state, manganese sulfate is a white powder with a pinkish shade.
When there's a shortage of manganese compounds in the human body,
it is prescribed as a medicine.
With this substance, you can conduct quite an interesting experiment.
Obtaining from it a well-known substance:
potassium permanganate.
To do this, let's take a weak solution of manganese sulfate
and mix it with hydrochloric acid.
After that, we'll add a very powerful oxidant:
sodium bismuthate.
It is the only substance that can take away from the manganese
a whole five electrons,
oxidizing it to oxidation state of +7.
After adding bismuthate to the solution,
you can see a change of the color.
As the solution becomes purple,
it's a clear indication that the solution contains permanganate ions.
The only thing that makes it a less enjoyable reaction
are the floating flakes that are a mass of bismuthate
and the basic bismuth sulfate
that were formed during the reaction.
However, the solution can be eliminated of its color
simply by adding hydrogen peroxide,
which gives five electrons to the manganese,
and restores it back to its divalent state.
Just on its own,
the potassium permanganate is a very strong oxidizer.
And because of that,
its weak solution is still being used in medicine
for disinfection against bacteria and fungi.
It is inexpensive, and at the same time effective.
However,
because of some individuals who use it for other purposes,
such as producing drugs,
it was banned in many pharmacies of [diseased?] countries.
Also in the western countries,
it is still sufficiently being used,
for example,
for healing burns and water disinfection.
This substance is included in the list of essential medicines.
With this compound, you can conduct an interesting experiment
called the "chemical traffic light."
To do this, we'll make a weak solution of potassium permanganate,
and then we'll add an alkaline sugar solution to it.
In the alkaline environment, potassium permanganate
oxidizes the sugar.
Thus, recovering itself first to the green potassium manganate,
and then to the yellow manganate dioxide.
Also, the well-known reaction of
obtaining fire without matches
is never without a potassium permanganate.
Which is only a case of mixing it with glycerin,
and then waiting for five minutes.
After a time, the mixture ignites on its own,
and can even ignite a thermite
because of the high combustion temperature.
In this reaction, the potassium permanganate is an oxidizer,
and glycerin is a reducing agent,
the donor of electrons.
The reaction takes place in several stages,
but the end result can be written down with one or two equations.
Also, if you mix the potassium permanganate
and the concentrated sulfuric acid,
you can obtain a hazardous substance:
the manganese oxide VII (manganese heptoxide).
Therefore, I highly recommend you to avoid repeating
this experiment.
Manganese oxide VII is a green, odorless substance
which can also ignite any combustible material
after a simple contact with it.
For example, with alcohol the reaction
takes place extremely rapidly,
in which manganese oxide VII is reduced to manganese dioxide.
By itself, the manganese dioxide is an excellent catalyst,
meaning it is able to reduce the
activation energy needed for the occurrence of a reaction.
For example, under normal conditions,
hydrogen peroxide is stable, and decomposes
extremely slowly, almost not noticeable.
However, by adding manganese dioxide,
a rapid decomposition begins
of hydrogen peroxide into oxygen and water.
During this reaction, the mixture gets very hot–
almost bubbling–this property of manganese
dioxide is used in organic synthesis
for a more effective oxidation of organic compounds.
Also, a variety of alkaline batteries
are made on the basis of manganese dioxide.
However, the substance plays a role
of the oxidant, or cathode.
Nowadays, manganese metal
is mainly used in metallurgy.
It is added to the steel to increase the tension strength,
and also to remove the unwanted impurities of oxygen
and sulfur from it.
This metal also plays a key role
in the production of stainless steel and
railway rails.
Now you know a little bit more about one of the other metals.
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