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Distillation Lab

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
  • Glassware Overview 0:04
  • Heating a Sample 3:09
    • Bunsen Burner
    • Heating Mantle 1
    • Heating Mantle 2
    • Hot Plate
  • Simple Distillation Lab 8:37
  • Fractional Distillation Lab 17:13
  • Removing the Distillation Set-Up 22:41

Transcription: Distillation Lab

Hi, welcome back to www.educator.com.0000

Today, we are going to be talking about some laboratory techniques.0002

The first thing we need to talk about is ground glass glassware.0005

Most of our reactions that we run in organic chemistry use round bottom flask like this.0009

This is very convenient for mixing all your reagents and your solvent that is dissolved.0014

There are no crevices to get caught up in but they do not stand up very well.0020

We can use a cork ring like this to support it, when we want it on the table.0024

And then, now we are going to clamp it with a clamp, when we want to do something with it.0030

The neck of this is made as ground glass glassware.0036

These are very precisely manufactured.0041

Two pieces of ground glass fit together to make an airtight fit.0044

But when they are dry, you can see that they kind of get stock and they can get frozen together.0049

That is not good because these are very expensive pieces of glassware.0055

You want to handle our ground glass glassware very carefully.0058

Before we fit any two pieces of ground glass glassware together, all we need to do is we need to lightly grease the joints.0061

We are going to get some stopcock grease or something else like that that is in your lab.0068

All you need to do is apply a very small amount to the male joint only.0073

All the way to the top where it is the widest part.0078

You can see how it tapers down a little bit.0082

We are going to put it in the widest part here just a little bit.0084

And then, you see when you fit these two together and they slide around, 0088

you can see how fully it is coming up on the camera, you get you can see it turns transparent or translucent.0092

You can kind of see through where it is greased.0098

It is very easy to slide these against one another.0100

When you are fitting ground last pieces together, they already has these little grease sign.0104

You can see how instead of being very white, it is gray or more transparent.0109

They should fit together.0115

Every time we fit pieces together, we should only do that.0116

If they do not slide very easily and have a nice solid fit there, we should add a little more grease.0119

That means when you are disassembling then, these are going to be sticky with grease.0126

We want to make sure we clean them properly.0130

We need some organic solvent, something non polar to get rid of the grease which are very non polar.0133

Hexane is ideal, I have a little acetone just from home, some nail polish remover0139

Just putting a little of that, some organic solvent on a paper towel.0144

And then, we can wipe the joint and you see when it dries, it is going to go back to that clear, acetone is quite as good as hexane.0150

It is going to go back to that clear thing.0157

Clean the male joints, the female joins, to make sure they are not tacky and 0159

they should be that nice great color, when you are done as well.0163

That is called greasing you ground glass joints.0166

That is how we get proper airtight connections between joints.0170

Vapor wound not escape, the liquid vapors would not escape.0177

Also, you can even draw this under vacuum and you can have a complete vacuum seal just using this ground glass pieces.0182

The next thing we are going to talk about is, how do we heat a sample, if we need to heat a sample.0189

There are several different methods we can use.0195

Again, we can imagine that our reaction is in a round bottom flask, something like this.0198

We have this clamped to a ring stand.0206

We can use a Bunsen burner, this is something that is a great source of heat.0208

We would hook this up to the gas line and use a match or striker to light this.0213

In fact, I will give you a quick lesson.0219

There is a valve on the bottom here that controls how much gas is coming through.0221

You want to make sure you have turned this clockwise to totally close this first.0226

Then, hook it up to the gas, light your match.0231

And then, with your match held just next to where the gas is going to come out.0234

If you put it right over at the gas, the gas is going to blow out your match.0239

But just next to it and then slowly with your other hand, open up that valve so that you slowly let the gas out.0243

And, you and you can light the flame and then you can adjust this second valve allows how much oxygen is coming in.0251

This one is how much gas is coming in and that we can get that mixture, you have that perfect blue flame.0257

This is a great way to heat a reaction or a flask, or a solution is something.0262

Remember, for organic chemistry, many of our liquids or solvents are flammable.0269

Most of our solvents are flammable.0274

You would not use a Bunsen burner very often in your organic lab, unless you are doing, maybe a sting distillation or something, where we have water there.0276

More often, what we are going to use is something like this, a heating mantle.0283

This is simply, we have like an asbestos cover here, a flame proof cover.0288

Inside, there are wires, a choral of wires.0295

As we pass electric electricity through them, it is going to cause the wires to heat up.0298

This just becomes a little device that gets warm.0302

We sit our round bottom flask in there, nice and securely, and that heats it up without any flames or any sparks.0306

The problem is if we were to hook this up directly to the wall,0313

there would be just a constant supply of electricity here and it just get hotter and hotter and it would catch fire.0318

That is not good. 0324

We need to have some kind of regulator.0325

This is the cord that the heating mantle fits into.0328

It has a curved plug.0330

When you insert it into the curve plug then you twist it, and then it is going to lock the two in place.0332

Make sure you twist it. This is the plug that I’m not going to plug into a wall.0338

Instead, I'm going to have some kind of twist like this, a variac.0341

I’m going to plug it into this and then this can get plugged into the wall but now what we have here is a variable control of our electricity.0345

We can turn this on and the numbers dial something tell us how much electricity is coming to it.0354

It is going to say how hot our heating mantle is going to get.0359

Make sure that when you are using heating mantle like this,0362

that it does not get plugged directly into the wall, that is a significant safety concern.0365

Make sure instead it goes into a variac.0369

Sometimes, these all look very different.0374

Sometimes, these are big, very often heavy.0375

Here is another example of the heating mantle.0378

Instead of having a fabric con, this is a ceramic well.0381

This is nice, it fits a 250 ml round bottom flask but you can put in a smaller flask, 0385

or even a test tube, and then, fill the rest of this with sand.0391

That is a way that it can fit any size and that makes it very nice heating element.0395

But again, this has no controls on it, this would be something that you cannot plug in directly to the wall.0400

You would have to plug that into a variac as well.0406

Some units have the variable controller built right in.0408

This unit has heating, this is for a smaller flask.0412

It has the heating element in here but it also has the voltage control right on here.0417

If you see the dial on here, you can see that you are going to have some way of controlling how much heat goes in,0422

and then, this is a standalone piece.0426

Sometimes, we use hot plates as a way to heat solutions.0430

This is great if you have your solution in an Erlenmeyer flask, you can just that Erlenmeyer flask right on here, nice and flat.0435

That is a good way of heating things, specially, if we are doing a crystallization or something like that.0442

Some things are just hot plates, all they do is turn on and they get hot.0448

Some things are stirs, you know what stir does.0452

Here we have our clamp, our round bottom flask who is clamped on here.0455

It has got a magnetic stir bar in there.0459

When they turn this on, it will start to stir because as we are heating a solution,0461

remember, you want to avoid having hot spots.0466

We either have to have a boiling chip in there to promote even heating or we have to stir it somehow.0469

Most often, especially if you have a reaction going on, we will set it up with the stir like this.0476

Notice that this stir does not have to be touching the stir plate, you would still have room to insert.0482

If this is just a stir, you would still have room here to put a heating mantle here and stir it, and so on.0488

This and this heating up, but not the right size.0496

That is a great way to stir a reaction as it is going.0499

I think those are all the different ways of heating a solution.0505

We will see some different applications for heating a solution, 0507

either running a reaction or maybe running a distillation, or perhaps doing a recrystallization.0510

It all starts with the round bottom flask.0518

This is where we are going to hold the liquid that is to be purified.0520

Because this is going to be heated and this is going to be containing hot boiling liquid,0525

that is the most important thing to secure properly, fastened securely to a ring stand.0529

I’m going to be using a clamp to hold this.0537

Notice that the round bottom flask, every round bottom flask has a lip at the top.0541

You want to make sure the clamp goes underneath that lip so that they cannot slide through it.0546

It is proper placement of the clamp.0551

Also notice that for a ring stand, the base should be facing the same direction as the clamp.0554

If you have it twisted like this, that does not support it, that can trip right over.0561

Make sure the base is in the correct position as well, I have seen that mistake quite a few times, 0565

when I have students setting up a distillation apparatus.0569

We are going to secure a clam properly to the ring stand, that is step one.0574

And then, we are going to fit that with a distillation head.0577

All my joints have already been pre-greased.0581

When it fits on, it slides very nicely.0584

This has two parts.0587

One that go straight up, that is where a thermometer is going to go.0589

The thermometer has been fitted into a ground glass adapter.0593

Again, ground glass goes into ground glass.0596

Notice where my thermometer bulb is, I want the thermometer bulb in the proper position 0600

so that it can record the temperature of the vapors.0604

Vapors is going to hit and condensed.0608

We are going to get the temperature.0609

But we want to get the vapors as they travel to where the condenser arm is going to be.0611

If our thermometer bulb, we can just twist this to adjust it.0616

If it is too high, then we are going to be missing the vapors as they travel.0621

If it is too low, then that is going to be fitting into where the neck is already kind of constricted.0625

You are not going to get a good flow of the gas vapors.0634

It is going to condense, you are going to get a lot of reflux instead.0637

We want to make sure we place it, everything about the angle of this condenser arm.0640

We want to make sure that thermometer bulb is below but not where it is going to be constricted.0645

That looks like, it might be pretty good.0650

The next part is going to be our condenser arm.0653

The condenser has a hole that goes straight through it and that is where our vapors are going to come through.0655

And then, it is jacketed by cool water so the water never touches the reaction mixture, the vapors.0660

You might have more than one of these to choose from.0670

Some of these have a narrow bore and others have a wider bore.0672

The wider ones are for packing.0676

We want to get the narrow one so it is as efficient as possible, when it cools.0677

We are going to fit that on here.0682

Again, twist to make sure they have a good fit and then we can use a cap clip.0684

These clips will hold these two glass places in place.0691

That is handy because otherwise it is easy for this joint to come loose.0695

It is very handy to use this clip, if you have one.0699

There is a wide part and a narrow part.0703

There is a wide part, a narrow part of the ground glass.0705

We are going to clip this on to hold those two conveniently in place.0707

It is also very convenient to clamp your condenser at this point0715

because the condenser is going to be filled with water which is going to make it quite heavy.0720

This is a good place to get a little bit of support.0725

It can be a loose clamp does not have to be held very tightly.0727

If you over clamp your system, it is really hard to get all of the ground glass joints to fit properly.0730

Loosen your clamp a bit for a little support.0734

What goes on next is called the claisen adapter and this is going to take our condensed vapors in the down direction.0737

Now I have to use a clip of some kind to secure these.0750

Make sure that you put the skinny part with the skinny part.0753

I have to use something to secure this because the claisen adapter is just hooked.0757

There is nothing holding it, it could very easily fall off if you do not have a clamp on or secured with rubber band or something.0761

Remember, a ground glass joint, ground glass glassware is very expensive.0767

We do not want to break that.0772

Absolutely, you have to have a clamp there.0773

And then, what are we going to collect in, I have this really low because all I need to do is use a round bottom flask here.0775

I made it a little too low.0781

We want to elevate this.0783

I forgot to mention that here.0784

We want to have some distance off of the bench top because we are going to have our heat source here.0785

We want to be able to raise and lower our heat as needed.0791

It should never be real close to the bottom.0795

But then, we also have to get a room at the other side for our collection container.0798

In this case, I'm using a round bottom flask.0803

We do not want to do that, if what we are collecting is quite volatile and has a low boiling point, 0807

then you might want to put this in an ice bath so that it stays nice and cold and stays liquid.0813

We could do that too, we could fit an ice bath in here.0820

I'm going to use another clamp to make sure it all stays together and it stays put.0823

This is our setup here, the next thing we want to do is get our water running.0832

We need some tubing and we want to fit each of these adapters with some tubing.0838

Put that on nice and firmly, so that it cannot pop off.0847

In fact, if you are running a distillation for long period of time or a reflux for a long period of time,0849

there are clamps you can get for this.0854

Or you can use wire to attach them because you never want these to pop off.0856

When it is unattended, not only you could have flooding problems but your reaction could burn dried,0860

if you do not have some way of cooling the vapors.0863

That would not be good.0867

That is more of an issue when you are in a reflux because that can go overnight or for several hours.0868

This is where we are going to run or water through.0874

This bottom one is where we are going to attach this now to a tap.0875

We want to always add water to the bottom so that it will fill up to the top and then drain out.0880

This top hose is simply going to go to a sink where it can drain out and empty.0887

Notice if you aim the adapters in the up position then you have more bubbles.0893

A common mistake is to put the water in the wrong direction.0899

If you have water coming in here, imagine, if you have water coming in here,0902

it would just pour straight out and empty out.0905

You would never get this filled.0908

Adding it to the bottom forces it to fill up and then drain from the top.0910

That way this is going to be a full condenser and it is always going to be cool to the touch.0915

You just need a very small amount of water.0919

After you hook up your hoses, very lightly turn on the water.0921

You just need a trickle going through.0924

If you put it too fast, you can have the tubing pop off.0927

Once your water is going on, before you start heating, you want to have a quick look through again,0934

your round bottom flask that has your distillation solution in here.0940

Make sure you have a boiling temperature tube.0945

If you are not going to be able to stir it, you want to have to have a boiling chip or two, 0949

so that we will ensure even hitting or would not bump.0952

Make sure this is nice and secure.0956

Make sure your ground glass joints are fitted together nicely.0958

Your water is running.0964

Then, we are ready to add our heat.0965

We can bring our heating in.0966

I’m using a heating mantle in this so that we can support underneath it.0968

Make sure that your heating mantle is not plugged into the wall.0973

But that it is properly plug into a variac, variable voltage regulator.0976

Very often, it is a really good idea to go through the whole apparatus with your instructor.0983

Before you flip the switch, your instructor will make sure you have everything properly put together.0988

When it is ready to go, then you can adjust your variable control, it will start heating.0995

Watch your distillation and see as it progresses.0999

Now if I wanted to do a fractional distillation, what is going to change about this apparatus is 1004

we are going to be adding this, this is a fraction heating column.1008

This is now has the wide bore condenser tube.1010

It has been filled with some kind of packing material.1015

These are glass beads, in this case.1018

What we are doing is we are introducing surface area for those vapors to hit.1020

If I can take this apart a little bit, your fractional distillation is going to end up being much taller.1025

You want to give yourself more room for that.1037

We are going to put the fractional column is right onto the initial round bottom flask.1042

This does not need to be clamped because it is being held on by gravity.1049

Again, over clamping, especially if you can cut them the perfect distance, the same distance apart can cause problems.1053

If you need to, loosely clamp it for support, if you feel better about that, that is fine.1058

But it does not really have to be clamped.1062

Our thermometer doctor goes on top up here.1065

What the fractionating does is, remember, as our hot vapors come up,1067

they are going to heat the packing material and condense, but then that is going to be hot.1072

It is eventually going to evaporate and then condense, evaporate and condense.1078

We call that reflux.1082

As it slowly moves its way up, remember, every time that evaporates,1083

it is going to be more further enriched in the lower boiling component.1087

You are going to, eventually, by the time it exits, the vapors exit the top here,1090

they are going to be pure compound.1096

I’m sorry, pure lower boiling point component.1100

Now we can fit on the condenser and again, the clamp here is going to hold it in place and make it less likely to come loose.1105

And now I have to bring my clamp all the way up here to clamp this loosely.1114

This is very important to make sure that this angle is that the natural angle you wants it to be with this steel head.1119

Put it in the right position and then move your clamp to fit that.1125

You do not want to clamp it and then not have it match the angle that it wants to be.1131

Now my flask is coming off here, you can touch it again.1135

You might be collecting this into a graduated cylinder.1140

For measuring volume or distillates, you might be collecting into some other container.1144

A round bottom flask is very convenient.1149

Again, this is something you can ice now.1152

With the fractional distillation, you are going to need to kind of build up something here.1153

Maybe a third ring stand to support your ice bath, if you are going to do that.1157

One thing to point out is when we use all these ground glass joints, these are airtight joint, 1161

you want to make sure you are not heating it sealed system, that would be bad news.1167

Because when you heat something, the vapors expand, you would increase pressure.1170

If you have a sealed system then it could explode.1174

Let us take a look at this, where is it not seal?1177

It is sealed all the way up here.1179

All the way up here, we have water coming around, jacketing this.1181

It comes in here and right at this point is where we have an opening to the atmosphere.1185

That is the part where this opening lets air exchange in and out, so that you never have pressure building up.1191

In fact, if you wanted to do a vacuum distillation, sometimes we have oils, very high boiling, 1200

and it is difficult to distill them without destroying them or degrading them, then what you are going to do is a vacuum distillation.1205

If I hook this up to a vacuum source, now this whole system is sealed and it is at a reduced pressure.1212

If I hit hook that up to a water aspirator, some vacuum pump or something like that, this is our reduced pressure.1217

Now my oil is going to evaporate in a much lower temperature.1223

It is often a challenge to keep this whole apparatus hot for the fraction distillation,1229

because we want it to reflux but we want it to eventually make its way up here.1233

A lot of times, we can grab some aluminum foil and jacket this loosely.1237

You can jacket it at the bottom, you can jacket it all the way up the top here.1245

We want it to stay hot and this is where we want it to condense.1249

You can jacket that all.1253

Aluminum foil conduct heats, it does not insulate.1254

We are doing it loosely so we are packing it with air.1260

This kind of stops the vapors, if you have run it near an air conditioning in your lab or something very cool.1263

This will just keep it warmer.1269

Ideally, if you can pack this with cotton or glass wall, and then with the aluminum foil jacket,1270

that would keep it really well insulated, depending on how hot you are boiling.1276

That is another thing.1281

As our distillation is proceeding, we are going to be keeping an eye in the temperature.1282

The temperature is going to give us some clue about what is distilling over.1286

If we are distilling over pure compound, the temperature should be nice and steady.1290

We are watching, we are collecting our distillate.1295

And then, if we noticed a change in temperature, for drops, or it starts to shoot up, 1298

then we could take off this flask and put on a new one, and then, collect the second component.1302

You know ideally in a fractional distillation, if you have two components,1307

you can distill off the first component, switch containers, distill up the second component.1309

And then, you would be able to separate your two liquids.1314

When you are setting this up too, one more thing about a fractional distillation is you want this to be vertical.1320

Take a step back and notice is it tilting further back or side to side.1326

If it is, then loosen your clamps and straightened it up, then tighten your clamps1331

because if it is at a steep angle, then you are just going to go out of reflux.1335

You distillation is going to take forever to go.1339

You want it to be nice and vertical.1341

Let us say our reaction, our distillation is done.1343

We have collected as much as we want.1345

Keeping an eye on the round bottom flask because we never want to distill the dryness.1348

If almost all of our mixture is gone or we have collected as much of what we want,1353

every different components, then we are ready to disassemble.1360

The very first thing you do when you disassemble is you lower your heat source and physically remove your heat source.1362

And that is why it is so important to have your initial round bottom flask clamped in an elevated position.1369

Because you need to be able to get the heat source in and out easily.1376

We need to totally remove it because just turning it off is not going to do the trick.1379

Just like if we turn off the oven, if you are baking cookies, if you turn off the oven, your cookies is still baking right.1383

The oven is still hot.1387

You have to turn off your heating mantle but then make sure you remove it so this whole system can start to cool.1389

You want the whole system cool, before you disassemble it.1394

Because if I start taking this apart, then these hot vapors are now going to be filling up the room.1397

Let this cool.1403

As it cools, you can touch it and you can use a little beaker of cool water.1404

Eventually, you have a nice bath to make sure it is super cool.1410

Depending on how volatile your compounds are, you know how much care you need to take and how cool it needs to be.1413

Finally, once it is totally cool then you can take off your receiving flask and then go analyze this and read it.1418

Disassemble everything and then we are going to not only clean the glassware but then remember there is grease in all these joints.1427

We need to get some hexane on a paper towel and clean all those joints very nicely,1433

so they are not sticky and they are ready for the next use.1438

I think that covers the basics for distillation, our fractional distillation.1443

I hope that was helpful and good luck with your distillation in the future.1450