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Introduction to Extractions

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Extraction Purify, Separate Mixtures 0:07
    • Adding a Second Solvent
    • Mixing Two Layers
    • Layers Settle
    • Separate Layers
  • Extraction Uses 1:20
    • To Separate Based on Difference in Solubility/Polarity
    • To Separate Based on Differences in Reactivity
    • Separate & Isolate
  • Theory of Extraction 3:03
    • Aqueous & Organic Phases
    • Solubility: 'Like Dissolves Like'
    • Separation of Layers
    • Partitioning
  • Distribution Coefficient, K 5:03
    • Solutes Partition Between Phases
    • Distribution Coefficient, K at Equilibrium
  • Acid-Base Extractions 8:09
    • Organic Layer
    • Adding Aqueous HCl & Mixing Two Layers
    • Neutralize (Adding Aqueous NaOH)
    • Adding Organic Solvent Mix Two Layers 'Back Extract'
    • Final Results
  • Planning an Acid-Base Extraction, Part 1 11:01
    • Solute Type: Neutral
    • Aqueous Solution: Water
    • Solute Type: Basic
    • Solute Type: Weakly Acidic
    • Solute Type: Acidic
  • Planning an Acid-Base Extraction, Part 2 17:34
    • Planning an Acid-Base Extraction
  • Performing an Extraction 19:34
    • Pour Solution into Sep Funnel
    • Add Second Liquid
    • Add Stopper, Cover with Hand, Remove from Ring
    • Tip Upside Down, Open Stopcock to Vent Pressure
    • Shake to Mix Two Layers
    • Remove Stopper & Drain Bottom Layer
  • Reaction Work-up: Purify, Isolate Product 22:03
    • Typical Reaction is Run in Organic Solvent
    • Starting a Reaction Work-up
    • Extracting the Product with Organic Solvent
    • Combined Extracts are Washed
    • Organic Layer is 'Dried'
  • Finding the Product 26:38
    • Which Layer is Which?
    • Where is My Product?
  • Tips, Tricks and Warnings 29:29
    • Leaking Sep Funnel
    • Caution When Mixing Layers & Using Ether
    • If an Emulsion Forms

Transcription: Introduction to Extractions

Hi, welcome back to

Today, we are going to be talking about using liquid-liquid extractions to isolate compounds.0002

An extraction is a way to purify and separate mixtures.0009

What we are going to be using for liquid-liquid extractions is a separatory funnel or sep funnel for short.0014

I have a picture of it here.0019

Let us assume that we have a mixture of two components A and B that are dissolved in some solvent.0021

What we are going to do is we are going to add a second solvent which now will be immiscible.0029

Typically, we have an aqueous layer and an organic layer.0034

We have two layers now.0037

We are going to shake the separatory funnel.0041

And then, we are going to mix the two layers.0043

When we mix those two layers A and B, components A and B0044

are going to be partitioning between the two different layers.0049

They are going to be separating out.0051

Once the layer settles, we are now going to have something that prefers this top layer A.0055

It will predominantly be in the top layer.0061

B, it seems prefers the bottom layer.0063

It is predominantly in the bottom layer.0064

When we separate, if we draw off that bottom layer into an Erlenmeyer flask,0067

we now have B in the Erlenmeyer flask and A is still in the separatory funnel.0071

We are going to have one component is in our first solvent and the other component is in our second solvent.0076

Where can we use extractions?0083

If we want to separate the two components, two or more components based on their solubility 0086

or maybe their polarity, that is what we use when we do liquid-liquid extraction.0092

Like I said, when we have an organic layer in an aqueous layer.0096

You can also use solid-liquid extraction.0099

If you have ever made tea or brewed coffee, the solid tea leaves contain organic compounds.0102

And then when you boil that into boiling water,0111

that water is going to extract the water soluble components and that is what makes the tea.0115

We all have done extractions before in your life, that would be a solid-liquid extraction.0121

In the lab, typically, we will be doing liquid-liquid extractions which is the aqueous and the organic.0127

Sometimes we can also separate components, based on their reactivity.0133

We call that an acid-base structure.0136

We are going to explore that today as well.0138

Our goal is to separate a mixture of compounds.0142

One other possibility is to isolate your product from a reaction work up.0146

After you have run a reaction, we can use extraction to separate your product from all the other components in the reaction.0150

You can also maybe use it to isolate a natural product, like I said with the tea leaves.0160

That would be a way of getting out some natural products like caffeine.0164

Many of the flavored components, you can extract them from the leaf 0168

or the bark or the tree roots or flower petals, something like that.0173

Extraction is a method for isolating the natural essential oils, as well.0178

What is the theory of extraction? How is this working to separate the components of a mixture?0185

Our dissolved compounds, we describe as the solutes in the solution.0190

They are going to partition between aqueous and the organic phases.0194

That process I had in the beginning, where A and B kind of separate out, we call that partitioning.0198

This is based on the rules of solubility, which is, like dissolves like.0205

Our distribution, we based on polarity.0208

Water is extremely polar so it is going to attract any ionic species.0211

Any salts are going to most definitely move to the aqueous layer, as well as extremely polar compounds;0215

where organic species are going to prefer the organic layer.0222

They are going to prefer it but they are not necessarily going to exclusively move to the organic layer 0224

because that depends on the polarity.0228

Some very polar compounds, organic compounds,0230

especially ones that contain a hydrogen bond like sugar, for example, is highly water soluble.0233

Not everything can be extracted completely with an organic solvent with a single extraction.0239

When you separate the two layers, you are therefore going to separate the components 0247

whichever ones are predominately dissolved in each of those layers.0251

Again, the concept of partitioning is important because we want to recognize that it is an incomplete transfer.0255

We are not 100%, something moving from one layer to the other.0263

Again, with salts, with ionic species, they will most likely transfer almost completely to the aqueous layer.0268

When it comes to organic compounds with different polarities, 0274

we are going to have it partitioning, separating out between both the aqueous layer and the organic layer.0277

Because of that, because when you do an extraction, only some of the organic compound will move to the organic layer.0284

It is common to do multiple extractions.0292

We almost never do a single extraction.0294

We use to do it two or three times to keep drawing out more and more of that organic compound into the organic layer.0297

That partitioning that we have talked about is described by a distribution coefficient given as k.0305

Multiple extractions are better because more would be transferred to the organic layer.0312

For example, let us assume that we have 10g of a compound A that is dissolved in the aqueous layer.0317

Each time we mix these layers, the A is going to partition itself between the two layers.0325

Each time, 90% of that compound A is going to move to the organic layer.0332

If we do a single extraction, starting with that 10g, 9 of those grams are going to move to the organic layer.0336

But 1g is going to remain behind in the aqueous layer.0343

If we do a second extraction, another 90% will be taken out.0347

Now 0.9g is in the new organic layer and only 0.1g remains in the aqueous layer.0352

If we now treat it with a third portion of fresh organic solvent,0357

then we will get another 0.09g and leaving only 0.01g behind.0364

If we did this process just once, we only get 9g.0370

If we proceeded and continue three times, we get 9.99g of the original 10g.0374

This kind of gives you an idea, emphasizes how these multiple extractions 0380

are going to help to try and get every last bit or nearly every last bit of the organic component out.0384

In equilibrium, we are talking about when we mix our two layers, 0389

we are establishing equilibrium between the aqueous and the organic phase.0393

At some point, after we have done a certain amount of shaking, no more shaking is going to change 0397

because the amount of A that is moving from the organic to aqueous 0402

is the exact same amount that has moved from the aqueous to organic.0405

It is the equilibrium that we are hoping to establish by mixing the layers.0408

Our distribution coefficient, our partition coefficient defined as k,0413

is calculated by the concentration of the solute in the organic phase divided by the concentration of solute in the aqueous phase.0417

Here is a picture of our components A and B, and how they are at equilibrium.0426

There are going to be moving from one layer to the other at equal rates.0433

If we have a large k, if it is greater than 1 that means your numerator is a larger number,0437

that means the compound prefers the organic phase.0442

If the k is less than 1, that means your solute prefers the aqueous phase.0446

That is going to be much more difficult to extract out of the water.0452

That is the case where now we want do multiple extractions0457

but maybe even something called the continuous extraction method, 0461

where you have your solid or your liquid that contains the solute.0464

We just keep heating it with fresh solvent, fresh solvent.0473

Even if just 2 or 3% of the compound gets extracted each time, overtime, we are getting it thoroughly extracted.0477

There are some processes out there, called continuous extraction, that are quite interesting.0485

Let us talk about acid-base extraction.0491

So far we are only talking about preference for the aqueous organic layer, 0494

depending on the compounds' polarity.0497

We can actually use the compounds reactivity, if we have a compound that is acidic or basic in nature.0500

Let us take an example, we have a mixture of two components.0508

One is an alcohol and one is an amine.0513

An alcohol does not have any significant, it is not a strong acid or a strong base, whereas an amine is a good base.0516

If we have a mixture containing these two, what we can do is we can extract that mixture0523

with not just neutral water but aqueous HCl.0529

Now we have an acidic component in our water.0533

When we mix those two layers, the amine and only the amine will get proteinated by the acid to give us salt.0537

Our reaction takes place between the amine, our NH₂, an acid.0544

This is acting as a base.0551

The HCl is acting as an acid.0553

We get a proton transfer reaction taking place.0560

We are going to get an amine salt, an ammonium salt as the product.0565

Now our amine group is an ammonium group.0570

It has got a positive charge and the Cl⁻, we have a salt.0573

Where do salts prefer to be in an extraction?0576

Do they prefer the organic phase or the aqueous phase?0580

When we mix these two, the salt is going to move to be aqueous layer, 0585

while the alcohol is going to remain in the organic layer.0589

With aqueous acid, we are going to successfully extract just the amine component 0593

out of the organic layer, by converting it to a salt.0598

Therefore, it has a preference for the aqueous layer.0602

Now we have separated these two components but we want to neutralize our ammonium.0606

Now to the aqueous layer, we are going to add in some base to neutralize it and0613

that will deproteinate the ammonium to get back to the neutral amine.0619

This is still on the aqueous layer.0622

Now if we treated this with organic solvent, we could extract it back into the organic layer.0625

Presumably, the neutral amine will prefer the organic layer.0630

It is only the proteinated amine that prefers the aqueous layer.0635

What we do is we neutralize and then we back extracted into some organic solvent. 0639

Now we have our neutral amine isolated as well.0645

Ultimately with this procedure, with this strategy, we are going to be able to have isolated both the alcohol and the amine0648

from where we used to have them mixed in a single organic layer.0656

Let us think about overall planning an acid-base extraction.0663

We have looked at one example, what if we have an amine where there are other types of reactive functional groups0666

that we can exploit using an acid-base extraction.0672

For example, here are the types of solutes you can have, 0676

so called neutral functional groups in which you have no significant acid or base properties.0680

Alkaline, alcohol, ketones, aldehydes, alkali halides, esters, ethers, etc. 0686

These are ordinary function groups that would all remain neutral and would always prefer the organic layer.0693

If we had an amine that is a basic functional group, so that is something that would react with an acid.0699

And then, we have some acidic functional groups.0705

We have things like phenols.0707

If you have a benzene ring with an O8, that is called the phenol.0709

These are weakly acidic, they are slightly acidic.0712

We can have carboxylic acid which are significantly more acidic.0717

A phenol has a PKA, just a PKA somewhere around 10.0721

A carboxylic acid has a PKA somewhere around 5.0727

This is 10 of 1000 times more acidic having a carboxylic acid.0730

These acidic components would react with any base that is present.0736

We would get a proton transfer that way as well.0740

Let us think about how each of these different components 0743

would interact with various types of aqueous solutions we can have.0746

We can try and extract just with water or we could use aqueous acid, 0751

mild aqueous acid, solute aqueous acid, something like 10% HCl.0755

Or a strong base like 10% sodium hydroxide or a mild base like an aqueous bicarb solution.0759

What are we going to get when we mix these altogether?0768

How about if we had a neutral component, how would any of these functional groups0773

ever be extracted into the aqueous layer, depending on whether we use water or acid or base?0779

The answer is no, these are organic molecules and they are going to prefer the organic phase.0787

We get no reaction, in this case, and that means it stays in the organic layer.0793

No reaction, whether if it is water or a mild acid or dilute acid or a strong base or a mild base.0806

In each of these cases, these neutral components would always remain in the organic layer.0815

Also, if we are to just look at water as the second layer, the aqueous layer that we have in our sep funnel,0822

that would never work to extract any of these organic compounds.0833

Water has no reaction with a basic component or weakly acidic or a more strongly acidic organic functional group.0838

If we use water as our aqueous phase, all of these organic molecules would stay in the organic phase.0850

None of them would transfer to the water phase.0858

But it is going to change now, when we start to have some functional groups that have acid-base properties.0861

It is going to change when we use acidic or basic water.0866

Let us think about an amine, what kind of aqueous solution would the amine react with?0870

The amine is a base that means it can accept a proton.0875

If we were to treat it with an acid, we would expect a reaction to take place.0880

Here is our acid, we would expect the RNH₂ group to get proteinated.0884

You will get RNH₃ which means now this moves to the aqueous phase.0892

Just like the example we saw in the previous slide, when we extract with 10% HCl, 0899

we would expect this amine component to leave the organic layer and move to the aqueous layer.0906

But if we were to use a basic aqueous solution, that would have no reaction with the basic amine.0912

The amine would stay in the organic layer in those cases, because there would be no reaction.0918

What if we had an acidic component?0926

If you have something that is weakly acidic, only weakly acidic, we expect it to react with the strong base.0927

The AR OH would get deproteinated.0935

If it is an acid that means it is a proton donor.0939

The base can remove that proton and we would get the salt.0942

Now that we a salt, this moves to the aqueous.0947

But if we try to use just a mild base, it would not react with the mild acid.0953

That would not be sufficient to extract it from the aqueous layer.0959

Of course, if we use an acid solution that would make no difference because two acids do not react,0964

that would be no reaction as well.0970

Finally, let us take a look at a stronger acid like a carboxylic acid, that would not be extracted up by neutral water,0972

that would not be extracted out by acidic water, whose two acids would have no reaction together.0980

But as soon as we put it in either base, either a strong base or a mild base,0987

we would expect the carboxylic acid to be deproteinated.0992

We start with RCO₂H and we end up with RCO₂⁻.0996

That is going to happen with both, with either base, any type of base.1002

That is where it moves to the aqueous and it moves to the aqueous.1007

Thinking about that reaction, spend a little time looking to start thinking about it developing on your own.1015

Understanding the various ways that the different functional groups are going to react1020

with a different types of aqueous solutions we can have.1025

Now that we see what the general reactivity is, now let us say we had a mixture of all of these.1029

With an alcohol and an amine, ethanol, any carboxylic acid.1037

What if we had all four of those in our reaction, extremely organic layer.1041

Is it possible to extract them out one at a time?1045

Can we plan our acid-basic extraction that way?1049

We can and here is how we would do it.1051

What we would do is our first extraction would be with a mild base like a bicarb.1055

Because the only thing that would react with is the carboxylic acid, the strongest acid in the mixture.1060

That is going to convert it to the carboxylate salt.1066

Therefore, it is going to be extracted out and it is going to move to the aqueous.1069

Again, do a couple of washes, a couple of extractions with the bicarb to fully extract all of the carboxylic acid.1073

Then, we move on to a stronger base like hydroxide and do several extractions with that.1083

What that is going to do is now react with any phenols that are present.1089

It is going to deproteinate those, transfer those out to the aqueous layer.1093

Now all we have left in our organic layer are any amines or neutral functional groups that we have left.1097

What is our next extraction going to be?1105

Now we treat it with acid. If we now extract with HCl…1107

Now the amine is going to get proteinated, converted to a salt, extracted out to the aqueous layer.1112

And then finally, the only thing left in the organic layer is any other functional group1117

besides amines or phenols or carboxylic acid.1123

There is nothing we are going to do to extract those out.1127

Those simply stay in the organic layer and now we have effectively separated all four components.1130

Now what do we do with these three aqueous layers, the separate flasks that we have?1136

We would neutralize each of them to make them neutral.1141

We would add base to neutralize this amine.1144

We would add acid to neutralize the phenol, an acid to neutralize the carboxylic acid.1147

Now all elements are all neutral, now we can extract each of those solutions with an organic solvent.1152

Those would move back into the organic solvent.1157

The goal in the end is to have our compound in an organic solvent1159

because the organic solvent is something that we can remove because it is volatile.1162

And then, we would end up with our final product in a flask isolated by itself.1167

How do you perform an extraction, what is the general technique that we have?1175

In general, you are going to pour your solution into a sep funnel so there is a stopper that comes off here.1180

We are going to make sure our stopcock is closed.1186

This is the valve that allows the solution to pass through.1190

We are going to make sure the stopcock is closed.1196

We are going to put this on a ring to support it.1197

And then, we are going to pour our mixture in here.1200

You can use a funnel to avoid spills.1203

And then, you are going to add your second liquid.1207

Remember, we are going to have an aqueous and an organic.1210

When you add your second liquid, you should watch to see -- does it float on top 1211

or does it sink down to the bottom when you add it?1216

You should watch that and confirm that it is going to where you expect it to go.1218

For most organic solvents, like ether, ethyl acetate, those are less dense than water.1222

We expect them to be the top layer, hexane.1228

Almost always the top layer for organic, but certain hydrogenated solvents like methane chloride 1230

or chloroform are more dense than water.1236

They sink to the bottom layer.1238

Occasionally, your organics are going to be at the bottom.1240

Again, you just want to watch as it goes in, be sure which layer is which.1243

We are going to cover it with a stopper.1249

We are going to add the stopper and we are going to hold it securely with our hands,1251

because we are going to be tipping it over and we never want this to leak.1254

We will hold on to that.1259

As soon as we tilt it over, we are going to open up the stopcock to vent any pressure that is building up.1261

As our solvent is mixed, they are volatile, they are going to build up some gases.1267

We always want to be able to vent this.1271

We always want to point this away from our face so that in case, a little liquid spits out, it does not hit you in the face.1273

We are going to aim this away.1280

I would be wearing safety goggles and a lab jacket, if I were doing this for real.1282

But this is empty, I'm okay.1287

We are going to vent it often.1288

Then, we are going to gently mix our first, venting often.1291

Then, we can mix it a little more vigorously, once we are closer to equilibrium.1294

Finally, when we are ready to separate the layers, we need to remove the stopper.1302

Watch our layers separate into two layers.1307

And then, we can use to stopcock to drain this out into an Erlenmeyer.1309

It is a good idea to always have an Erlenmeyer flask underneath, 1313

in case this leaks or you accidentally had this open, the Erlenmeyer flask is going to collect any spills that you have.1315

Another significant use for extraction, we use it all the time in the lab, is when we do a reaction work up.1325

That is the kind of process we use to isolate and maybe you get to purify a little bit of your product.1332

Most organic reactions are run in organic solvent.1342

Some kinds are ethyl acetate or hexane or ether or methane chloride, varieties can be used.1346

Usually, when we say a reaction is done, I want to start my work up process and I start my product.1354

Very often, the first step is to add water to your reaction mixture.1359

It can either be just water itself or can be used acidic or basic, depending on what your reaction’s conditions are.1363

What that water is going to do is it is going to quench any reactive species.1370

Maybe, you are doing a Grignard reaction, you want to get rid of that excess Grignard reagent.1373

You want to provide a proton source to proteinate that O⁻ that is in the final intermediate.1378

The water is also going to dissolve any inorganic salts you have.1386

For the Grignard, we have magnesium, salts, and so on.1389

That is going to dissolve those and separate those from your product as well.1393

Now we want to isolate our products.1399

What we are going to do is extract our product from the aqueous layer.1400

We are going to add some additional solvent and mix and separate.1404

Then, add some additional organic solvent, mix and separate.1408

Again, by doing multiple extractions, we are going to move all of the products as much as possible,1412

out of the aqueous phase and into our organic phase.1416

Then sometimes, we take those combined extracts, typically, we wash them with various aqueous solution.1420

Maybe, if we use acid in that first step, we can do a bicarb base wash to get rid of any excess acid.1427

We can do various washings.1435

I'm calling this extraction process a washing, because what we are doing is we are removing unwanted material.1437

We describe it as an extraction, when we are removing what we want to isolate.1446

The same process of mixing two layers and separating the layers but it is going to be described differently,1450

depending on whether taking up the thing we want or taking out something that we do not want.1457

Your organic layer is always going to be wet.1465

We describe it as being wet because it has dissolved water.1469

It has just been mixed with our aqueous phase over and over.1473

We need to remove that water, before we can remove the organic solvent.1477

That is called a drying process.1481

There are several steps you can do for this.1483

One thing to remove the majority of water is we can use a brine wash, that means just saturated aqueous NaCl.1486

We have our combined organic layers.1492

We add in some brine and we mix the two.1494

By osmotic forces, that brine is going to draw out the majority of the water from the organic layer1498

because that water would prefer to be with the brine.1504

That will remove most of it.1507

To remove the trace amounts of water, we typically use solid drying agent,1508

something like calcium chloride, sodium sulfite, magnesium sulfate.1513

We pour our organic layers out into an Erlenmeyer flask.1517

We add in some drying agents and wait.1522

What happens is that drying agent, all these species are very good at absorbing water.1526

It is going to suck the water out of the organic layer.1530

As it does so, it clumps up and you can watch as you add some in and swirl around, 1534

it sticks to the sides or sticks to each other, these solids.1540

Then, you add a second portion and you swirl it around and you watch.1544

Maybe add a third portion, swirl it around and watch until eventually 1547

that last portion you add does not clump up with the rest of the pieces.1550

It remains freely flowing and that tells you that your solution is adequately dry.1554

There is no more water left to absorb.1558

It is not an instantaneous process, especially, depending on what solvent and drying agent combination you are using.1562

You want to make sure you wait several minutes to ensure that your solution is completely dry.1567

Once it is dry, we filter off the drying agent, filter it into a tared round bottom flask.1572

And then we remove the solvent, typically by using something like a rotary evaporator or rotovap1577

to under reduce pressure very quickly, remove our solvent.1582

Ultimately, here we have in our round bottom flask, we have our reaction product isolated and fairly clean,1586

compared to all the mess that you had in your reaction mixture, what is called a reaction work up.1593

A couple of hints in finding the product.1601

One concern you might have or confusion that occurs sometimes in an extraction is which layer is which.1603

If we get confused which is the organic, which is the aqueous layer.1610

What you will always do is just add a few drops of water and watch where that water goes.1613

Does it stay on top, does it dissolve at the top layer?1617

Or you see little drops traveling all the way through the bottom layer? 1620

That will confirm which layer is which.1622

Once you draw your layers out and now they are in flasks, it is very easy to forget who is who.1626

You do not want to start working with the wrong layer to continue on with your procedure.1632

It is great to have a Sharpie marker in the lab.1636

Just draw out little something down, write on the glass saying aqueous, organic, brine, so on, because that will avoid confusion.1638

The biggest thing is never ever discard any layer, throw out any layer, 1649

until you are absolutely sure at the end you have your product in hand.1654

That is the biggest rule, is to keep everything until you are done.1658

Because if you had made a mistake somewhere, that is okay if you can step back and find the correct layer that you are missing.1663

But if you throw it out then there is no going back.1671

Make sure you label things to keep track and do not discard anything until the very end.1674

Another question is, let us say we did my whole work up procedure and I put it in the rotovap, 1681

and I do not get any product or I get very little product and we are expecting a lot more in our organic residue left over.1685

Maybe, you need further extraction.1693

Maybe, you did not mix properly or mix long enough to achieve that equilibrium.1695

You can go back and extract some more.1700

Maybe the solvent you used was not an effective one.1702

Maybe you need something that is more polar or less polar to better extract your product.1704

You can also, if you have a compound that is quite soluble in water.1710

What you could do is you could add sodium chloride to your aqueous layer.1716

This process is described as salting out.1719

By doing that, you decrease your compound solubility in the aqueous layer.1723

By adding NaCl to your aqueous layer, it now has ions in there.1728

It is significantly more polar.1732

That can kind of help push your organic product into the organic layer and increase that affinity.1735

And therefore, increase your kp and get more product extracted out.1743

That is called salting out.1746

We might do that for compounds that are quite water soluble.1748

Once again, never discard any layer until your product is recovered because maybe you accidentally,1752

you used one of the organic washings on the rotovap, instead of your organic extractions that you really meant to.1758

That is another good reason to be able to come back and double check your work.1764

Finally, some tips and tricks to ensure successful extraction.1770

This stopcock piece can come out completely.1774

If this is not been secured, it can be very loose and it can leak even though it is closed.1779

Make sure you tighten this valve to make sure it is secure and going to be watertight,1785

and you are not going to have any leaking solvents.1791

Again, that is why we always keep the flask underneath, in case it does leak, you can catch it.1793

I do not think there is a chemist alive who at some point in their career has not accidentally had the stopcock open, 1799

when they introduce their solvent to the sep funnel.1806

We all make that mistake and that is okay, because if you always have an Erlenmeyer underneath, that mistake is not a costly one.1809

Be very cautious when you are mixing layers because pressure can build up.1818

You can have your stopcock until you can have the stopper blow off at a minimum.1825

But if there is a flaw in the glass, for this can actually explode, this can break.1830

If you just shake and shake and never vent, you just start building up pressure.1836

That is the most dangerous thing we are doing here with our sep funnel process.1842

We are going to be venting often.1845

Especially, when we are using a bicarbonate as one of our aqueous layer because this releases CO₂, when it neutralizes.1848

Now you are really having, it can foam and you can really build up your gases.1858

Again, very gentle, slow mixing with constant, frequent ventilation.1862

You want to make sure that you are always dealing with cool solvents, cold solvents.1868

If you have a warm aqueous layer for some reason, and you add ether to that, ether is quite volatile.1872

It is going to shoot right out the top or just evaporate so quickly that everyone in the lab is going to get an instant headache.1877

Make sure that you are never making that mistake.1883

Remember that ether is very volatile, the vapors are flammable.1886

If we are doing an ether extraction, we just always want to be double, extra certain, 1889

that there is no flames around, there are no sparks around.1894

We do not have any hot plates around.1897

All of those can be sources of flames.1900

Also because it is so volatile, ether is another one that really builds up pressure quickly.1903

We want to shake very slowly and vent regularly.1908

A common problem that occurs in extraction is an emulsion.1912

An emulsion is when instead of having a clear organic layer and a clear aqueous layer, 1916

it is all one layer or you might have the organic and aqueous and this third area in the middle, that kind of blended the two.1922

Our goal is to have two distinct layers.1932

It is called an emulsion, when you mix oil and water and they do not separate.1936

Like when you mix salad dressing, if you mix that up, the two layers come together and 1941

it will stay that way, if you add in an emulsifying agent.1947

Those are things that help aqueous and organic layers mix.1949

If you are using hand lotions or creams or something like that, those are oil droplets in water1953

but they stay there because of the emulsifying agents that are in there.1958

Sometimes the components of your reaction act as emulsifying agents and cause emulsions to occur.1962

This is a common thing that can happen.1972

We want to know how to deal with it and you can look up some several strategies for that, some ideas.1974

One thing is just let it sit, swirl it every once in a while to help the two layers separate.1980

But sometimes, it is just a patience thing, they will eventually separate.1985

You could add a little sodium chloride or maybe few drops of ethanol by changing the polarity of the solvent.1989

You can cause them to not like each other so much and therefore they will more likely separate into separate layers.1996

Sometimes you have particulates in your reaction mixture.2004

Just fine little particles.2009

Those particles can also hold the two layers together and cause an emulsion.2011

Sometimes you just want to take your entire mixture, both layers, and pass it through a Buchner funnel, do a vacuum filtration.2016

That is going to separate, that can out any of those little particulates.2022

And then, when you pour it back into the sep funnel, you might find that it separate more easily into two layers.2025

Or you can just transfer it to a flask and let it sit overnight, more time, rather than they are in the sep funnel.2032

A lot of strategies that I’m sure if you Google how do I get rid of an emulsion,2038

you will find more ideas, then you know what to do with it.2043

But the key is to find something to try and try it, so that you can keep moving forward with your lab.2045

I hope you learned something about how extraction works and how we might need it,2051

and how we can now use it in a lab, and that how to do it safely.2058

I wish you luck in your extractions in the future.2064