In this video, you're going to learn how to use a Burette.
Before watching this video, make sure
that you've watched the "Meniscus",
"Transfer Pipettes", and "Mohr Pipettes" videos.
This is a Burette. As you can see it looks very similar
to a Mohr Pipette. Burettes are typically used
for titrations and are used to transfer
very accurate and precise volumes of liquid.
Looking at the top of the burette, you'll notice
the first graduation is zero, just like with the Mohr Pipette.
But as you move down, the volume increases.
You'll notice near the bottom of the burette
that the graduation stops.
This is the same as a mohr pipette,
the liquid should never go below this level.
In order to determine the volume of liquid
transferred in the burette, the difference between
the final and initial volumes will be taken.
At the bottom of the burette, there's a stopcock.
This allows you to control the amount of liquid delivered.
When it's horizontal, the burette is closed.
But any variation from this flat angle
causes liquid to leave the burette.
The first thing to do before you start using your burette
is to make sure you have the proper setup,
just like I have here.
You'll need a retort stand, a burette clamp,
and your burette. You should make sure you always use
the proper clamp, or you can break the glasswear.
Next you should make sure that there's no damage
to any part of your burette.
If there is, just tell your TA and get a new one.
You now need to clean your burette.
To do this, remove it from the clamp gently.
Make sure that the stopcock is completely closed,
and add some deionized water to the top of the burette.
This is very similar to cleaning a pipette.
You want to hold the burette with two hands
to make sure it doesn't break, and gently rotate it,
making sure that the water covers
the entire inner surface of the burette.
Once you've done this, gently place it back
on the clamp, and place the waste beaker
underneath the tip.
You'll now want to drain most of the solution
from the burette into the waste beaker.
To do this, gently turn the stopcock.
Don't drain all of the solution out,
leave a tiny bit in the bottom of the tip,
because this allows the prevention of bubbles.
If you find that the stopcock is too difficult to turn,
you can adjust it by turning the knot
one direction or the other, to loosen it or tighten it.
Gently touch the tip of the burette to the side
of the waste beaker to remove the last drop.
You'll want to repeat this process 2 more times
with the deionized water to thoroughly clean the burette.
You'll now want to clean it 3 times with your solution.
You have to do this a little differently
because your solution is not in a squeeze bottle.
So you'll want to lower your burette
so that the top of it is at eye level.
You don't want to pour any solutions above your head
because this can be dangerous.
It's okay that the tip of the burette
hangs below the bench, just make sure
to be careful and not to break it.
Place the funnel in the top of the burette,
make sure you cleaned it first.
You can now pour a small amount of your solution
into your burette.
To do this, and make sure the funnel properly drains,
it's important to raise it up a little bit
to let air into the burette.
You can now rinse your burette the same way
you did with the deionized water.
You'll now want to fill your burette with your solution.
You'll do this the same way you did
when rinsing it with the solution by
lowering it over the edge of the bench.
Now using the same funnel, fill your solution
above the zero graduation mark.
Make sure not to pour too quickly
because you don't want to overflow your burette.
This will cause the solution to spill over the floor.
Once your burette is filled, raise it back
to its original position,
and place the waste beaker under the tip.
You'll now want to let a small amount of solution
drain to prevent the formation of any bubbles.
Leaving a small amount of solution in the burette
like I mentioned before, should have prevented
any bubbles from forming.
But always make sure to check before you begin.
Lower the liquid level to below the 0 line.
It's important that your initial volume is below the 0 mark,
because if it's above, you won't be able to
to get an accurate initial volume reading.
When you're ready to go, remove your waste beaker,
gently touch the tip to remove the last drop,
and replace it with your receiving vessel.
Erlenmeyer flasks are typically used when using a burette.
Adjust your burette to make sure that the
tip of the burette is well below the rim of the flask.
This prevents the loss of any solution
when it's flowing out of the burette.
You should position the burette so that
the handle of the stopcock is on the same side
as your dominant hand.
To properly use the burette, you'll need to hold
the stopcock with your non-dominant hand
and the handle should be between your thumb
and index finger.
With your palm around the back of the burette.
This may feel uncomfortable at first,
but with proper technique, and
will feel more comfortable with practice.
It provides support for the stopcock,
and it frees your dominant hand
to swirl the receiving vessel
while you're adding solution to it.
Now that you're set up, record the initial volume in the burette.
If you have difficulty reading the volume,
use the card shown to you in the meniscus video
called the "Burette card."
Burettes are extremely precise, and the volume
measurements should be made to one-tenth
of the smallest graduation.
You can see here that the meniscus lies between
the 0.8 and 0.9 graduation marks on the burette.
Because the graduations do not get any smaller than this,
the last digit is estimated.
The volume in this burette can be read as
0.83 milliliters.
Hold the flask with your dominant hand,
and begin to turn the stopcock with
your non-dominant hand as demonstrated earlier.
While swirling the flask, it's important to make sure
that the tip of the burette is well above
where the solution is, you don't want to
submerge the tip.
Once you've transferred all of the solution,
return the stopcock to the horizontal position.
You can now rinse down the sides of the flask
to make sure that all of the drops of solution
from your burette makes it into the bottom of the flask.
Let the burette settle for a few seconds,
and then record the final volume.
Taking the difference between the initial
and the final volume will give you
the volume transferred into your receiving vessel.
Once you've finished using your burette,
make sure to drain the remaining solution.
Do this through the tip and not the top.
Then you'll want to rinse it the same way as before,
only rinsing it first 3 times with tap water,
then 3 times with the deionized water.
For the most thorough clean, you can
remove the stopcock.
To do this, unscrew the blue nut.
Then remove the black and white plastic rings.
To keep these safe, make sure to keep them
in a clean, dry beaker.
You can now pull the stopcock from the other end.
You can rinse the inside of where the stopcock was,
and also all of the pieces of the stopcock.
To place it back in the burette, first insert
the large plastic piece, followed by
the white plastic ring, the black rubber ring,
and finally, the blue nut.
Your burette has now been thoroughly cleaned
and can be stored for later use.
To store your burette, you'll want to make sure
that the stopcock is completely vertical
so that it's completely opened,
and you'll want to store it upside down.
This prevents build-up from forming in
the stopcock, and it also allows
all of the water to drain.
Using a burette is something that's very common
in all forms of chemistry.
It can be daunting at first, but with a lot of practice,
you can master it!