Lithium peroxide is a strong oxidizing agent with the formula
Li2O2.
It readily reacts with CO2 in the air and for this reason it's commonly used
as an air purifier.
Unlike other CO2 scrubbers it has a very low molecular weight which makes it
particularly useful in spacecraft.
On top of this it also has the added benefit of releasing oxygen gas.
To make the lithium peroxide I use two main chemicals, 35% hydrogen peroxide and
lithium hydroxide.
The hydrogen peroxide was purchased from the store and the lithium hydroxide was
made in a previous video starting from lithium metal.
I honestly didn't really need to make it myself and it can be pretty easily
purchase from eBay.
The procedure that I'm following for this preparation is from a patent and
I'll provide a link to it in the description.
To start things off I added a hundred and twenty five milliliters of
thirty-five percent peroxide to a beaker.
The next thing that we need to do is add about 50 grams of lithium hydroxide.
I turn my stir plate and with vigorous stirring we can start to add the lithium hydroxide.
Immediately after adding it, it will start to react and produce lithium hydroperoxide.
Things will slowly heat up as we continue to add the lithium hydroxide
and some of our hydrogen peroxide will start to break down.
Hydrogen peroxide is quite sensitive and it pretty easily breaks down into water
and oxygen gas.
So the bubbling that you see here is actually the release of oxygen gas and
the solution isn't boiling.
The addition of the lithium hydroxide will heat things up and we want to keep
the temperature below something like 60 C.
After adding a decent amount of lithium hydroxide the stir bar started to have
some troubles, so I had to dilute things with a little bit of distilled water
It took about 20 minutes but we eventually add the last bit of lithium hydroxide.
The reaction mixture is then covered with plastic wrap and we let things stir
for about 15 minutes.
When I come back 15 minutes later things have taken on a very slight yellow color.
The beaker is then transferred to a hot plate and we heat things up to about a 100°C.
The moment the temperature reaches a 100°C we take it off heat and we
pour it into a vacuum filter funnel.
A vacuum is pulled to remove the liquid and we should be left with our lithium
hydroperoxide on the filter.
On top of the hydroperoxide we actually have a few chunks of lithium hydroxide
that didn't react. So using a scoopula
I quickly get rid of them.
The hydroperoxide in the filter is then broken up using a glass stir rod.
The next thing that we need to do is convert the hydroperoxide of lithium
into the actual peroxide that we want.
This conversion is carried out by heating the lithium hydroperoxide while
under a vacuum.
So what I'm doing here is transferring the hydroperoxide into a round bottom
flask and then I'm going to pull a vacuum and heat it up over an oil bath.
These are set up where the flask is under vacuum and we have an oil bath at
around a 120°C. The dehydration of the hydroperoxide to the
peroxide, is pretty uneventful and visually not very much happens.
I heated it under vacuum for about an hour and when I was done I was left with
a nice dry powder.
The lithium peroxide was then transferred directly from the flask to a
storage container.
The final yield was about 25 grams which corresponds to a percent yield of about
fifty two percent.
The patent that I was following advertise a yield of about eighty three
percent, so a yield of 52 is a little bit on the low side.
Before proceeding on to doing any experiments the first thing that I'm
going to do is make sure that we actually have lithium peroxide.
In order to do this I'm going to carry out a very simple peroxide test.
To carry out the test we need to first prepare the test solution which involves
mixing about one gram of potassium iodide in about ten milliliters of
glacial acetic acid.
I use a glass stir rod to mix things up but most of the potassium iodide is going to
remain unresolved.
We're done making our test solution now and all we need to do is add a little
bit of our alleged lithium peroxide.
When a small amount of the lithium peroxide is dumped in you can see that
immediately it starts to take on an orange yellow color.
This color change occurs because the peroxide is a strong oxidizer and it
oxidizes the colorless I minus ions to colored I2.
With this positive result we can move on and experiment a little with the lithium peroxide.
The first thing that I wanted to do was to test out the CO2 scrubbing
capabilities of the lithium peroxide.
To carry out this simple test I started by filling two test tubes with some CO2 gas.
To the tube on the right I then added probably way too much lithium peroxide.
To test out the tube that contains only CO2
I light a match and put it inside. The match is extinguished almost immediately
when it comes into contact with the CO2.
Now when we try it with the tube that has the lithium peroxide we can see that
the match actually maintains a flame for quite a bit longer.
And a CO2 only atmosphere like in the other tube the match would have been
extinguished almost immediately.
So this is a good indication that oxygen is being produced.
I went ahead and try to reignite a burning stick but there just wasn't
enough oxygen to get a flame going again.
It we look at the equation of the reaction between the lithium peroxide
and CO2, we see that to moles of CO2 are used and it produces one mole of oxygen.
Gases at room temperature tend to occupy the same volume and this means that if
we're absorbing two moles of CO2 and only producing one mole of O2, we will
let most be filling half of the tube with oxygen.
Even if all of this you two were consumed we get a maximum oxygen
concentration of about fifty percent.
Given that we have a maximum concentration of about fifty percent,
it makes sense that we're not seeing the reactions we do when we have a tube
filled with pure oxygen.
Anyway with that being said I'm going to move on and do some flame tests.
For the flame test I put a little bit of the lithium peroxide on the bottom of a pan and then
I shot it with a blowtorch.
The important thing to notice here is the characteristic crimson red color of lithium.
I also tried to add a little bit of organic solvent to the peroxide and
light it on fire.
I tried with a few different common solvents and nothing really happened in
each case.
I didn't film it but there were a few times where I gotta pop but that was
probably the most that happened.
I thought it was going to be much more reactive and I was really surprised when
I saw that not much happened.
As a final experiment I added a little bit of lithium peroxide to some hot water.
When it's added two hot water it very quickly reacts to form lithium
hydroxide and oxygen gas.
Anyway that's it for now and the next video that i'm going to be posting is on the reverse
aldol cinnamaldehyde to make benzaldehyde.
As usual like to extend a big thanks to all my supporters on Patreon and especially
those who donate five dollars or more.
Anyone who donates and supports my Patreon gets to see my videos 24 hours
before I release it to youtube. And if you donate five dollars more you get
your name at the end of the video like you see here.
In the next few months though I want to work on my Patreon page a lot and I want
to get more rewards going and maybe even get some higher tier ones and I want to
also offer some Patreon exclusive content.
Also as usual here's the videos that I've currently filmed and the ones that
plan to work on.
If you have any suggestions or ideas please feel free to leave them in the comments.