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[MUSIC PLAYING]

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PRESENTER: It is used to
determine the concentrations

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of various solutions.

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In this video, we'll take you
through the proper procedure.

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The number one
rule of titration.

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[ALARM BLARING]

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A quick review of
burette preparation.

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Please see the volumetric
techniques video

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for more information.

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Here is the titrant
you'll be using.

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Take your burette and fill
it with a few milliliters

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of titrant.

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Then tilt and rotate the burette
to coat the interior surface

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with titrant.

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Finally, allow the burette
to drain completely,

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then fill to above the 0 mark.

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Firmly and securely clamp
the burette to its stand.

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Hold on a minute, there
are air bubbles in the tip.

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We can't have those.

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In order to get rid
of them, quickly

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rotate the valve back
and forth, letting

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small amounts of liquid pass
through the tip intermittently,

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then slowly drain your burette
to 0, or at least close to it.

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It is not vital that
you drain to exactly 0

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so don't spend all your
lab time doing this.

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Drain to relatively
near it and just

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be sure to record your
starting level of titrant.

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Let the burette
stand for one minute

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to allow drainage from
the interior walls.

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But wait, an idea.

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Before you start your
titration, why not

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try an initial rough titration.

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It really will help.

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With this, we want to get an
idea of where the endpoint is.

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So here we go.

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But wait, it's overshot.

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What?

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How'd that happen?

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[SHOUTS]

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No worries.

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It was a rough titration to
get an idea of the end point.

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Be sure to take note
of how much titrant

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you used so you have
a rough idea of when

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you're near the end point
during the actual titration.

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So let's discuss the end point.

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You really should know
what you're shooting for.

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Here are three titrations.

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Which one has a barely
detectable shade of pale pink?

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Hint, that's what
we're looking for.

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Ta-da, there are your
answers, the middle one.

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It's perfect.

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Here's the undershot one.

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Obviously, it needs more base.

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And here's the overshot one.

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Too much base.

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This time, going above and
beyond is not commendable.

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But here, it's perfect.

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It's a clear solution with
a barely detectable shade

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of pale pink, just
what we're looking for.

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So now we know what we're
aiming for, we can move on

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to the actual titration.

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Hang on to your lab coats.

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Wee!

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First, record initial
burette value.

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Remember, you don't
have to start at 0.

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You could start here,
or here, or even here.

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It doesn't matter.

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Just be sure to record
the starting value.

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Here is our indicator.

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This allows color
changes to be seen.

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You want to add one or
two drops to the solution

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depending on what
kind of acid it is.

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The titration can be
carried out rapidly at first

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since you have a
general idea of where

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the endpoint is due to your
rough titration earlier.

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Always remember to swirl after
each addition of titrant.

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Notice how the color
disappears upon swirling.

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But when you know you're nearing
the end point, what should

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you do?

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Well, when near the
end point, slowly add

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titrant in small increments.

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Closely monitor
any color changes.

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Small increments can
mean one drop at a time.

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Remember to swirl
after each addition.

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Since we want to
reach the end point

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within a fraction
of the drop, we

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need to slowly
approach the end point.

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How do we do it?

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Well, we could use the
plastic tip, as seen here.

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This allows for
smaller drops to come

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through the tip of the burette.

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And this is the parafilm that
will secure the plastic tip

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to the burette.

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First, you want to
take the plastic tip

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and fit it onto the burette,
then take the parafilm

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and wrap it around the tip
and the tip of the burette.

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You must stretch the
parafilm in order

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for it to adhere to the glass
burette and the plastic tip.

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Stretch and wrap,
stretch and wrap,

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then tear off the
end when you're done.

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Make sure it's firm and secure
and then readjust the burette.

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But before you start to
slowly approach the end point,

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remember to empty air
bubbles from the plastic tip.

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But you may be wondering,
what is the difference

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in drop size anyway?

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Take a look here.

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These are drops from
a regular burette tip.

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And here are small drops
from the plastic tip.

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Notice their size compared
to the regular burette.

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So you think you've
reached the end point.

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You must take care
of one last thing.

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There is that last drop.

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In order to make sure you're
reading the burette properly,

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you must pick up this drop.

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Use the inside
wall of your flask

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and touch the tip
of the burette.

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This picks up the drop and
allows it to run down the side.

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Make sure you tilt, rotate,
and swirl the flask in order

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to pick up any stray drops
that are on the inside walls.

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You can't let those
renegade drops get away now.

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But have you really
reached the end point?

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Make sure it's a clear solution
with a barely detectable shade

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of pale pink.

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Also, the color
should be persistent.

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That's when you know you've
reached the end point.

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But be careful, end point
color is not permanent.

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It will disappear within a few
minutes due to carbon dioxide

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absorption from the air.

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So now, it's time for
wrapping things up.

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Let the burette
stand for one minute

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to allow drainage from
the interior walls,

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then record the
final burette value.

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Subtract the final volume
from the starting volume

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and you'll have the
amount of titrant used.

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Ta-da!

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Now you're capable of
making your TA's dream

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titration come true.

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Good luck!

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Remember, this video
is intended to help

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you prepare for lab by
providing a demonstration

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of the proper
experimental technique.

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It is not intended
as a replacement

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for reading your lab manual
or the supplementary material.

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In order to become a
great experimentalist,

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it is important that you
understand both theory

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and technique.

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Now, it's your turn.

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Good luck.

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[MUSIC PLAYING]