Greetings fellow nerds.
In this video we're going to make manganese sulfate which we'll need in upcoming videos.
And I’ll show you two ways of doing it.
One using sulfuric acid and oxalic acid, and another using sulfur dioxide.
First, an important distinction.
Manganese sulfate is not magnesium sulfate.
These are two different chemicals, not an alternative spelling as some believe.
With that cleared up, let's start.
My source of manganese in this case is the manganese dioxide we obtained from batteries in another video.
I wanted to use pure stuff but was unable to obtain it as seen in a previous video.
So here is my stock.
Now onto the first step.
The first thing that needs to be done with manganese dioxide is thoroughly wash it with water.
Here I got about 500mL of water
and I’m adding about 100g of manganese dioxide from the battery.
I'm going to let it stir for half an hour to thoroughly break up all the chunks.
Once that's done, simply filter it out.
As you filter, add water to thoroughly wash out the soluble contaminants like zinc and ammonium chloride.
Once that's done you'll have a wet battery paste that actually consists of manganese dioxide
along with a large amount of carbon as well as a few other contaminants like iron oxides.
You don't have to dry it, just go to the next step.
In the first method to convert it to manganese sulfate you start with 30 grams of oxalic acid,
add about 200 mL of water, and then add 13 mL of concentrated 98% 18 molar sulfuric acid.
Stir it up.
It's going to heat up a lot when you add the sulfuric acid.
Add another 100mL of water and stir to get as much of the oxalic acid dissolve as you can.
It won't all dissolve but that's fine.
Now get the paste of manganese dioxide and carbon and start scooping it into mixture.
What's happening is the oxalic acid is reducing the manganese dioxide
and then reacting with the sulfuric acid to form carbon dioxide.
The result is manganese sulfate and water.
The carbon dioxide can be seen here bubbling out of the mixture.
This provides an indication of when it's done.
Just keep adding the black paste and stirring until it stops bubbling.
It's impossible to say exactly how much you'll need,
because all batteries are different and the state of charge before opening the battery also has an effect.
Just keep going until it stops fizzing.
For the amount of acids in this video I needed about 100g worth of battery paste to react it.
Anyway, once it's finished, just filter it through.
Boil the filtrate to concentrate it, but don't boil it all the way,
or else it'll start popping liquid at you.
You should now get this pink solution of manganese sulfate
with a small amount of iron contaminants that were present in the original paste.
Try and stick to right ratio of oxalic acid, sulfuric acid and water.
I found that if you use too much of either of the acids, or too little water,
a lot more iron gets dissolved alongside the manganese sulfate,
and you'll have a yellow solution that's massively contaminated with iron.
I don't need to purify it since I’m going to use it to make electrodes
but if you want to know I’ll make a separate video.
For now, let me move on to the second method of making manganese sulfate,
which is cheaper and actually better as well.
For the sulfur dioxide method
I first got another 100g of washed manganese dioxide battery paste.
Here it is in a 500mL round bottom flask
and mixed with water to create a slurry about 300mL in volume.
Now I need to bubble in sulfur dioxide
and in a previous video I made a sulfur dioxide generator
using sodium metabisulfite and hydrochloric acid
along with some specialized glassware.
In this video I’m going to instead use burning elemental sulfur for the sulfur dioxide since it's cheaper.
So here is the setup.
I got the manganese dioxide slurry over here and I’ve already placed a magnetic stir bar inside.
To get sulfur dioxide into the mixture I’m going to use a vacuum pump
and this specialized glass adapter.
Once it's sealed into the round bottom flask
a vacuum pump will pull sulfur dioxide gas down through this inner tube
where the gas exits and mixes with the slurry.
Any air or extra sulfur dioxide then rises out and is sucked into the vacuum pump.
Ok let's put it to use.
Here I’m installing it onto the round bottom flask.
The adapter is attached by a tube to the glass funnel,
which will help collect the sulfur dioxide.
This here is our sulfur candle.
It's nothing more than a tin can filled with 50 grams of sulfur and brown paper towel as a wick.
It's an excess of sulfur since some of it will inevitably be lost
through the inefficiency of collection in this crude setup.
Anyway I've turned on the vacuum
and you can see considerable bubbling in the flask as the air is being pulled through.
All that's left now is to light our sulfur candle and let it burn producing sulfur dioxide.
Placing the funnel over it the sulfur dioxide is being pulled into the slurry.
What's happening is the sulfur dioxide is directly reacting with the manganese dioxide
and producing manganese sulfate.
Now I waited for the candle to burn down completely which took about two hours
so I’ll skip over that.
Here we are.
You can see the funnel is lined with soot and ash from the burning sulfur and paper towel.
This is why I prefer this vacuum setup to pull gases through the system
rather than using a gas pump right after the burner
as the pump would be clogged with all this soot.
Anyway here is our finished reaction mixture.
Simply filter it out and already you can see it's a nice pink color.
The iron in the battery paste is not dissolved even though an excess of sulfur dioxide was used.
This is the advantage of the sulfur dioxide method in that not only is it cheaper,
but it's also much more forgiving of unknown stoichiometry and purity.
Now once again, boil it to concentrate it and let it evaporate to crystallize slowly on it's own.
There is still a little iron contamination so for extra purity do a recrystalization or two.
And there you have manganese sulfate.
We'll be using this along with a few other chemicals to make manganese dioxide electrodes in an upcoming video.
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