How to Use a Volumetric Pipette

here we have three ways of measuring out

25 milliliters of liquid the 25

milliliter beaker the 25 million

cylinder and the 25 milliliter

volumetric pipet the difference between

these is the beaker will measure 25

milliliters the graduated cylinder will

measure 2 25.0 milliliters and the

volumetric pipette will measure 2 25.00

milliliters so the difference here is

the beaker only gives us two significant

figures the graduated cylinder gives us

three significant figures and the

volumetric pipette will give us four

significant figures so to get the most

accurate and precise reading possible

we'll be learning how to use the

volumetric pipette correctly today the

first thing when getting your volumetric

pipette is to clean it with water

because you do not know what

contaminants are on the inside when you

are using your volumetric pipette always

make sure to have one hand secure on the

volumetric pipette and the other hand

secure on the bulb do not assume that

the bulb is going to be holding the

volumetric pipette these are only

supposed to be gently fits in with one

another they will not hold if you just

try holding the biometric pipette with

only the bulb this bottom part will drop

out and it will break so please make

sure that you always have one hand

secure on the pipette itself so when

you're cleaning this out the first thing

you want to do is just squeeze the bulb

and then suck up some water and you only

have to get about half filled here

and once you're satisfied with that you

can just hold it over a waste beaker and

then just swirl it around to make sure

that the water contacts all the insides

and then just let it slowly drain out

and keep spinning it just to make sure

that all the inside surfaces have been

thoroughly washed and once you're done

with that just let the water drain out

and just let it do it naturally and you

may do this one to three times however

many times it takes you to be satisfied

that the inside is actually clean this

particular one is actually pretty nice

and clean here so we don't need to do

much more with that all right you may

notice that there's a little liquid it's

okay to blow this stuff out now because

we don't want to give this diluting our

next sample now after you've rinsed your

pipette with water you also want to

rinse it with the solution that you're

going to be using to avoid any dilution

of the solution from residual water left

in the pipette so you only have to again

fill this up about halfway

so right there is about that we want to

try minimizing the waste that we

actually have and then at this point

again this is going to be over your

waste speaker just swirl this around so

this way it kind of coats the interior

surfaces and any water that was in there

gets rinsed away and once you're happy

with that just let it drain into your

waste container

now once all that is done we're ready to

get our solution alright now that we've

rinsed it we're ready to fill it up and

what we notice is that there is a line

right about here and this is the line

that we want to fill up to so we want

the bottom of the meniscus to match up

to where this line actually is so again

making sure you have one hand secured on

your pipettes press out your bulb and

then start sucking your liquid this may

take two or three times depending upon

you know how successful you are so that

time I didn't get a quite filled so

again I just again hold it over here

with my index finger and then I just

press the bulb again and then suck up

some more liquid

so you'll notice that right here is

where my line actually is and what we

want to do is get it from up here down

to my line so you simply just hold this

over your waste container and from your

finger up here just slightly release it

not all the way but you just want it

loose enough so then some air can get in

and your liquid starts draining down and

you just let it drip down until you're

able to see where it matches up so the

meniscus is matching up with the line

right now as you can see right there the

line and the meniscus are all lined up

so now we simply just hold it over our

vessel and just let it drain and this

may take about a minute for it to fully

drain here

okay now when it's fully drained you'll

notice that there's a little bit of

liquid in there now what's actually

going to happen is is I'm standing here

you'll probably start noticing a little

bit of a drop forming on the outside

that's because the liquid that's

actually like adhering to the outside of

the glass is actually draining down here

and is actually going to start putting

this liquid out so you want to wait

about thirty seconds for that additional

liquid to come out and actually here you

can see the drop which is starting to

emerge so obviously you won't always

have this over your container not in

front of the camera but then just let it

drip out and then when that final drop

actually comes just touch it to the side

of your container and just let it fall

in all right now at this point you'll

notice that there's still a little bit

of liquid left in there we don't want to

go and blow that out even though you're

gonna be very very tempted to the reason

is that these pipettes are designed to

deliver me and that they're designed to

leave that little bit of liquid left in

there and not have it being blown out so

even though it's very tempting please

make sure that you do not blow that out

and put it into there because right now

this contains 25.00 milliliters of

liquid if you add that little bit extra

it's gonna be over and we simply just

don't know how much it will be by so

then at the end of the day when you are

done with this make sure that you rinse

it out with water and that's the same

procedure that we started with so again

you will just go there suck up the DI

water make sure you hold it over your

waste container and spin it around a

little bit and then just let it drain so

this way it washes out and as nice and

clean for the next person okay and that

is how we use our volumetric pipettes