I'm trying to make some citric acid.

I could do this with lemons.

I could do it with mold.

Which one am I going to do?

Don't matter because it's going to be easy either way.

So we going to do both.

Juice from lemons and limes is like 5 to 8% citric acid, which that ain't bad.

That's a that's a good amount of citric acid, but you can get way more citric acid into a solution by having a bunch of mold ferment sugar into citric acid in that solution.

It's just faster, it's easier, it's more efficient, and you don't have to grow a bunch of fruit to do it.

But, yeah, I'm going to outsource the fermentation part because thankfully I know somebody who knows how to do that.

The mold that we're looking for is called Aspergillus Niger.

If you've ever seen, like black powdery mold on an onion, that's what we're looking for.

So the actual first step is to find an onion that had a bunch of this black mold on it.

So just imagine me at the grocery store looking around for the grossest onion.

Once I found the mold, I needed to grow up enough of it to actually start a culture.

And I did this using potato dextrose media.

Really, what I did here, I made it myself.

I boiled a bunch of potatoes, I filtered out all the chunks, and then I added some sugar.

And then I have a media that the Aspergillus will grow in.

But I wanted to start it on a plate, so I stamped my onion top onto some plates like this.

After I let that sit for a while.

Oh, it's so gross.

Then I grew some Aspergillus Niger.

It's kind of crazy because you grow plates upside down so that they don't flood when like the water cycle happens.

So looking at it from the top, the Aspergillus first looked white and I was like, oh, I grew the wrong thing.

And then I flipped it over.

And there is our there's our black mold.

Once I had enough of the black mold to start a culture that I needed to give it something to ferment.

So the fermentation broth uses molasses as a sugar source for the Aspergillus.

But the problem is that a lot of molasses contains some metal ions that can interfere with.

So I dropped my mold into my conditions, let it sit and ferment for a few days, ideally inside the broth.

Whole diagram is happening.

We have glucose turning into citrate.

And like pyruvate CoA is in there.

And like the Krebs cycle is there.

And the whole gang from biochemistry is here.

But I can't see if any of that is happening.

All I know is that I grew some more mold, and now I'm giving the mold broth to Chem Thug to see if we can get any.

I hope so.

Before I can get the citric acid out, though, I got to check this mold bar for this other acid, oxalic acid, because that one might mess me up later.

Oxalic acid kind of shows up as a byproduct of the fermentation, and it will also bind to calcium, which is what I'm going to do in the next step.

Now, once I add this calcium hydroxide solution, if there's oxalic acid in here, we should see some solids precipitate out and I don't see anything.

Nah.

It's is not that happening here.

I got this citric acid solution from the citrus juice and the mold broth.

Right.

And I need to get the citric acid out of the solution.

And I'm going to do that by turning it into something that can't stay dissolved in the water.

And that's more or less the heart of this whole process is like playing with the solubility and controlling the solubility.

The first step is sodium hydroxide.

This here is a strong base.

It's going to pull all the protons out the citric acid that will let me pull the sodium citrate out of solution as something slightly different.

The sodium hydroxide is also going to react with a lot of other things in the lemon juice though.

And why the color changes because a couple of those things, when the pH gets high enough and the solution is basic enough it goes from like that yellow color to that orangy color.

I now have my solution free of lemon bits.

Mostly just, you know, sodium citrate and a bunch of other things that I don't care about.

Right?

But I can get the sodium citrate out and leave all the other stuff behind by converting it to calcium citrate.

So I'm going to add some calcium chloride.

And calcium is going to attach itself to those citrates.

It's going to kick the sodium off and it's going to grab onto those citrate.

And it's going to do that because when it does that it falls out of solution as a solid.

Right.

Love this precipitation.

Yo I love precipitation reactions.

They're so gorgeous.

But this is now a solid that I can filter.

Definitely did not settle nearly as much as I hoped it would over the last two days that I left this.

I guess my vacuum pumps just about to be real busy.

Filtering that solid, by the way.

Oh man.

Yeah.

That that that took way too long.

Way, way too long.

So I repeated the process a few times just to make sure I got as much as I could out of this.

You know what I mean?

I do want as much citric acid as I can, so I want to do that.

I might be leaving some calcium citrate But here we are with, you know what we got?

It is not an amazing amount, but it is what it is.

Now, now I got to do the same thing with the mold broth.

And this is more or less the same thing.

It's just a slightly different mess, I'm going to shortcut it and I'm just going to make it basic with some calcium hydroxide.

Because the calcium hydroxide is still a base and it will still pull the protons off the citric acid and make me that citrate.

But it comes with the calcium.

You feel me?

So the calcium will just react right away.

And I get my calcium citrate.

Now I just got to give it a heat and once I do that, you're going to start seeing the calcium citrate crash out.

Which here.

Yeah.

No, this is this is going a little faster than the than the lemons.

That's nice.

I definitely take that.

So now, if you use molasses as a feedstock, you know, I mean, you're going to get it looking like this is going to look ugly and gross, and the molasses is just going to stick to everything, I mean it is molasses and it's kind of ugly.

Yeah.

And it's definitely contaminated.

Sure.

But like in industry, they do it this way.

And also like they they clean it up better and it's going to get cleaned up, you know, I mean it'll it'll definitely be cleaner by the end of this process for sure.

Now, same deal with the lemon juice.

I'm going to repeat the steps a little bit just to make sure I'm squeezing everything I can out of this bro, too.

Now, I mean, I want to get all the citric acid I can at the end of this, especially because the liquid still looks kind of cloudy, which kind of means that there might still be some in there.

But compared to the lemons, the mold broth has done this much faster and with way less effort, I just.

I just wish that the solid was pure calcium citrate.

But it's not.

It's calcium citrate with the molasses stuck to it basically.

But hopefully it's not going to be a problem later.

And the next thing we're going to do is flip this calcium citrate back into citric acid.

And to do that I'm going to add some sulfuric acid to it.

Ooh, can you hear that?

It got dramatic quickly.

What's going to happen is the sulfuric acid is going to give its proton to the citrate and turn the citrate back into citric acid that's going to dissolve.

Actually the foam is probably just the calcium citrate itself puffing up from like, you know, the water that's now boiling off but not yet reacting or turning into calcium sulfate, which is what you get when you do this reaction.

Calcium is going to get kicked off.

Except once it gets kicked off, it's going to go hook up with the sulfate, which is left over after the sulfuric acid does its thing.

And they make this stuff calcium sulfate, which is also just like water insoluble, just like the calcium citrate.

Get it to about boiling and let it boil for about an hour.

And that way I make sure that, like, all the sulfuric acid I added reacts with as much of the calcium citrate as possible.

Which, remember, there's excess calcium citrate in here, which is going to get filtered out in the next step.

Yep.

That's right.

We got one more filtration to do before we're done.

Stay tuned.

You were promised the filtration.

Here is that filtration.

So here I got a bunch of citric acid mixed with other stuff that's making it yellow.

I couldn't tell you what the other stuff is, but once I poured this into this beaker and boil off some of this water.

Eventually, well, first, a little bit more calcium citrate and calcium sulfate is going to come out.

So I'm going to have to filter it one more time.

But it's going to be quick.

But then then once I get the volume down to maybe, like, I don't know, 200 mL from the 600, then you're going to start seeing the citric acid crystallize out.

Yeah, that's what we're going for.

So now I got that calcium citrate from the mold broth and I'm going to turn that into citric acid using sulfuric acid again because the chemistry is going to be the same no matter where the calcium citrate comes from.

As long as I do it right.

Yep.

More filtering.

So much filtering.

This is a large part of chemistry it just happens to be.

But then, then, I'm going to pour it out into a dish.

It slowly evaporates out after a little bit.

You're going to start to see the citric acid crystallize out.

It's quite a bit of solid, just like stuck to this bit of this glass.

None of it really looks obviously like citric acid.

So I don't really have instructions at this point, so I'm just going to lean on my general chemistry knowledge to try and get this cleaned up.

I rinse this with cold water to dissolve a minimal amount of my citric acid product.

And maybe I can transfer some of these solids to a filter paper.

I don't know, those look kind of.

Those look pretty clear and crystally.

I'm gonna test it and let's see if we got citric acid.

If it is, the solid will dissolve in water.

Okay.

Doesn't look like it's dissolving.

It's not a good sign.

I'll just test it with baking soda.

If it's citric acid, it should fizz.

Zero fizzing.

Boy.

This really has been a monumental disappointment.

I am deeply frustrated.

I'm like actually kind of upset.

I'm not going to cry about it.

I isolated so much material from this whole endeavor, and none of it is citric acid.

I think what I got was just too dirty and wasn't enough.

All right, let's see what the lemon's got for us.

Maybe the lemon extraction went better.

It's not dissolving as quick as I expect citric acid to dissolve that.

That is very true.

That's not a good sign.

Let's see what happens when I sprinkle a little baking soda on it.

Oh, there's some fizzing.

There's fizzing.

Not as much as I might expect that this is citric acid but why isn't it dissolving?

That's so weird.

I don't know what this is.

I don't feel like this is citric acid.

I'm going to do it again.

I've been working on this for two months.

I feel like I got to turn my degree in or something.

Because I'm pretty sure the answer is just that.

I didn't have enough calcium citrate to start with.

I'm not doing a comparing or testing chemistry anymore.

I'm just trying to make this happen.

I'm just, like, pissed, you know.

You've seen this part.

We just going to montage our way to 189g of calcium citrate.

Because I'm tight.

This should have worked.

I am pretty proud of myself for isolating all of this.

This is a lot of product.

But I'm not going to calculate the yield and make myself feel bad.

Instead, I'm just going to flip it again.

If I want to consume all of this calcium citrate that I got here, the full 189g or so, I'm going to need about 118g of sulfuric acid.

That is a horrifying amount of sulfuric acid to have to weigh out.

I'm chilling this sulfuric acid solution in some snow, because the colder it is, the less danger it poses.

I'm also putting the calcium citrate on the snow so that it's also very cold.

And when I mix the two it should be very calm.

It's definitely not being crazily dramatic.

It is so calm.

Then if you look close now, you can see that the solid in there is not quite as tan.

It's a little whiter and that's the calcium sulfate forming.

And that I'm going to just filter out.

So now I got to get this water out and I got to make the citric acid crystallize.

We just going to put it in a bigger drying dish.

I can't help but imagine, though, that this would have been way easier with the mold broth.

But anyway, we got these lovely square shaped crystals.

So cute.

Look at that.

And I'm pretty sure that's actually citric acid.

But of course, there was more calcium sulfate.

It's okay.

I've gotten very good at filtering and evaporating liquids at this point.

But this time I got me a fat solution.

I think I figured something out.

Citric acid does dissolve in acetone, but not nearly as well as it dissolves in water.

So what I think I can do here is crash more of it out with acetone.

This is so exciting.

This might be the end of this journey.

When I add this to this, I should get a whole bunch of solid falling out.

Oh, look at that.

It is phase separation.

The top layer is mostly acetone.

The bottom is a mixture of acetone and water.

As they're mixing, it's forcing the citric acid out of solution.

This is not a recrystallization.

This is very much a precipitation.

It feels like a mild miracle that I was able to make this happen.

I feel accomplished.

I feel super accomplished.

I'm going to take a little bit of this solid.

Throw it in this test tube.

Let's see how well this dissolves.

Oh, look at that.

Gone.

It's dissolved.

This is a monumental moment.

I would like to know if this fizzes.

Oh, there it goes.

It took a second.

It's fizzing.

And may not be pure.

It's definitely citric acid.

Now that I know what to do, I just want to make a giant mold broth.

I don't think I'll ever buy citric acid for my lab again.

Definitely still buy it to eat it.

I wouldn't trust myself.