Hello everyone!
I am going to tell about an element which in my opinion is the most colourful one and which is one of the most essential
micro elements in our organism. Today, we'll talk about Iodine.
I think many of you know, that seaweed is rich in iodine (as well as other seafood).
High concentrations of iodine in sea waters and in sea organisms
led to the discovery of this element in the beginning of the 19th century. By the way
When writing the script for this video,
I wondered why there is so much iodine in seaweed and what role it plays is these plants. The answer to this question
stunned me. According to the research conducted in
2008 lots of types of seaweed use iodine-containing
inorganic chemicals. For instance, such as iodides, to protect themselves from atmospheric ozone
in low tides a small amount which is present in the air.
Iodide ions in the cells of seaweed react with nitrogen in the air
forming aerosols from small particles of elemental iodine,
which is oxidised by ozone in the air and then dissolves in water
Thus seaweeds have adapted to the damaging effect of ozone,
which is formed within close proximity to water. Iodide was discovered, as you might have guessed, in
seaweed. For instance
if you take such a rich of iodine seaweed as gobo for wakame and burn it at a high temperature
and then add sulphuric acid to this ash a small amount of violet
Iodine vapors will be released. This is how elemental iodine was extracted for the first time ever.
However, today during the era of globalisation
iodine is no longer extracted from seaweed because doing so it is not very
cost-efficient. Nowadays iodine is extracted from ancient ground waters or from so called potassium ores.
It is very easy to extract iodine from potassium iodide. We just need to take some potassium iodide and dissolve it in water.
Fortunately, the taste of iodide is highly soluble in water.
If to add an oxidiser to this solution for instance potassium iodide,
there will be released a small amount of elemental iodine.
Pure elemental iodine is a dark hard chemical which has turned into such beautiful
crystals. In 20 years in this old jar most probably this
happened because of the sunlight or another source of heat which partly sublimed the iodine and such stunning dark
crystals grew out of it.
Elemental iodine is quite fragile. These crystals are very easy to break with pincers.
Which is why small pieces little by little sublime dyeing everything around in dark iodine stains.
By the way, speaking of sublimation,
elemental iodine has an interesting property.
It easily transitions to a gaseous state and forms beautiful violet iodine vapours.
Let us run an experiment. I'm putting small iodine crystals into a glass and cover
the glass is a rounded glass flask filled with ice cold water.
I'm heating up the glass over a stove which is my iodine is quickly subliming. That is,
transitioning from a solid state to a gaseous state, skipping the liquid state upon reaching
114 degrees Celsius, it starts melting and quickly vaporising. Iodine boils at the temperature of
118 degrees Celsius. If the temperature of the stove is right, on the bottom of the glass
we can see a whole liquid iodine waterfall.
Its vapors rise up, but upon cooling
Immediately condense in the lower part of the glass. On the top we can see thin iodine crystals
grow downwards. Their shapes differ from the crystals in the jar which grew at a slower pace.
Apparently the pace at which crystals grow
affects their crystalline grids. And also keep in mind that these iodine vapours are quite toxic.
This experiment should be done in a fume hood. I let the glass cool for about two hours. After that
I decided to check on crystals. They grew three times their initial length
and now I have highly pure iodine without any inclusions.
Iodine crystals can also be used to produce a liquid iodine and it doesn't take much to do that.
We just need to melt a piece of iodine in a test tube and then just pour out the liquid.
Iodine in the (same?) container. I did that to show you
elemental iodine in a liquid state which is rarely seen because of the precise temperature of just
66 degrees Celsius at which iodine can be liquid in normal conditions.
I think this is the reason why there is a myth that
iodine doesn't exist in the liquid state, but rather it sublimes and forms vapour.
Iodine's property to easy vaporise can be applied in forensic science.
If to take some iodine tincture and add 2 teaspoons of
3% hydrogen peroxide and 1/4 spoon of citric acid treat in some time
In some time there will be released a small amount of elemental iodine.
If to carefully turn the glass upside down and put it on a sheet of paper with a
fingerprint, in some time, you'll see the fingerprint. That's because iodine dissolves
well in fat which we leave along with our fingerprints.
Speaking of the solid state of iodine
it doesn't dissolve well in water. However, it dissolves well in non-polar solvent for instance in alcohol or
hexane, I think you know that it dissolves well in alcohol because you can find tincture of iodine
practically in any Russian pharmacy. However, it is not sold as simple iodine dissolved in ethanol rather
it is a mixture of potassium iodide because it contains tri-iodide ions
which help make iodine more soluble in alcoholic solution.
Such iodine tincture can be used to make another organic chemical, which is iodoform.
We just need to add 10% sodium hydroxide solution
to a few millilitres of iodine tincture. a few seconds later
the solution will become colourless and there will be forming yellowish crystals of iodoform.
In mixtures with fillers such as glycerol and zinc oxide
iodoform is successfully used in dentistry as antiseptic paste.
Also, we can run an interesting experiment with different
solubilities of iodine.
First we need to chloroform into graduated cylinder because it is heavier
liquid then we need to add water and to top it with hexane if we add a few crystals of iodine
to these three layers of liquids we can see this element dissolve in
different layers of the liquids. The lower iodoform layer becomes dark violet.
The middle layer is slightly yellow and the top layer is pink. Judging by the colour,
we can conclude that
iodine dissolved best in the lower chloroform layer, a bit worse in the hexane layer and
almost didn't dissolve in water.
However, if to use sodium thiosulfate instead of water iodine crystals will dissolve well in such a solution.
Although this is a reduction of iodine to sodium iodide rather than dissolving and sodium
thiosulfate will be oxidising.
However, we are not done with running experiments with iodine yet.
It's time to demonstrate a classical reaction with this element
which is a reaction of iodine with
Aluminium. I have reduced a few crystals of iodine to powder in a mortar to make the reaction run
faster. Now I am mixing iodine with aluminium powder
which is very fitting for this reaction because this is a very fine powder. To start with,
I'm going to add a few drops of water and in just a few seconds, the mixture will self ignite.
In this reaction as well as in many other reactions with iodine, their forms a cloud of iodine vapour
which is so hard to stop looking at even for (an) experienced chemist.
By the way, a small portion of this cloud settled on the hood walls leaving striking stains.
But that's okay because
just a few hours later
Such things disappear on their own because of elemental iodine's high volatility.
We haven't finished obtaining iodine clouds yet.
If you remember a TV program on discovery called Brainiac from about 12 years ago,
you must remember Logan's Paste. To make that paste you just need to mix small crystals of iodine
with ammonia solution.
About 50 minutes later their forms nitrogen triiodide
which consists of unstable molecules . When it's wet, it's quite safe.
But when it is dry, it's a very unstable chemical.
After filtration
(we let) the filter with nitrogen triiodide
dry overnight in the laboratory. I strongly recommend you not to try this experiment at home because it's very dangerous
experiment. Now when the paste is dry, it's time to demonstrate how unstable it is.
It's enough to touch the dried nitrogen triiodide
with a thin stick.
The explosion was extremely loud and during this fast reaction nitrogen triiodide
split into gaseous nitrogen and elemental iodine,
which also forms such a violet cloud. This cloud of iodine is also very toxic.
That is why you should not repeat this experiment.
However,
elemental iodine is quite stable and doesn't oxidise when exposed to the air. If to run
experiments not with elemental iodine, but which its oxide, the reaction will get much more interesting.
The thing is, if you cut up hide in oxide it was played into oxygen and elemental iodine,
forming those beautiful violet fumes.
If we add water to the iodine oxide there will form iodine acid which can dissolve some active metals
such as magnesium for instance. In this reaction magnesium forms magnesium
iodide and also there are forms some elemental iodine. Iodine
Oxide is also actively reacts with iron the reaction runs when the mixture is set on fire.
Just like (in) the case with other reactions during this experiment, there forms vapours of elemental iodine.
In slow motion you can see that these fumes look stunning.
Speaking of the physiological properties of iodine, this element is essential for our thyroid gland
because it produces hormones regulate in metabolism such as thyroxine and triidotrionine.
That is the reason why people not live in within close proximity to the seas and oceans
try to consume iodised salt,
which is rich (in)potassium iodide in order for people to be able to reduce a deficit of iodine.
I think now I can end the video about this non-metal, with the heaviest atomic mass at
this point if you want to learn even more
I suggest that you watch other videos on my channel
related to this element
and also if you like this video
don't forget to give it a thumbs up and subscribe to my channel to see many more new and interesting (things).