[neilep (OP)]

See these Pipettes !

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Two questions ?

What determines the size of a drop out of each pipette ?..I presume different size ends will give different size drops yes ?


And..why are they called Pasteur Pipettes ?....did he also invent the Pipette ?...is it as simple as that ?

[Karen W.]

The top part of the squeezer portion and the thinner diameter tubes however minimal, add to, and determine the droplet size I believe!

[Karen W.]

The top has so much space to hold a certain amount of water thus the diameter of the tube can accomodate the bigger amounts of the water allowing a larger drop to be formed at tip.

I am not qualified to add my two cents, but that would be a pure guess and observation on my part! LOL

[neilep (OP)]

Seems like good guesses to me karen mam.

So, if the pipette could hold even more liquid it could eventually  make a very big drop ?...hmmmmmm !!!..

I thought the size of the hole where the liquid comes from might have something to do with it !!

[Karen W.]

Yes I think so two.. if you look at your three samples each hole is just a

tiny bit bigger, it seems to me, which would allow for more volume I

would think! Thus the reason for the bigger reservoir.At least that would be my guess. The tip size is almost unnoticeable..More water would be more weight per drop wouldn't it? So if the tips were all the same how could they accommodate the amount of water to enlarge the droplet size..

I think you are right!!!

[Karen W.]

So if the tips were the same perhaps it wouldn't matter how much water the bulb held because the tip would determine the amount that could actually pass through the opening..... You must be right!

[eric l]

I'm affraid most of the guesses are wrong.

• Pasteur pipettes are named after Louis Pasteur (http://en.wikipedia.org/wiki/Louis_Pasteur), who invented them, no doubt about that
• Pasteur's pipettes were glass pipettes with a rubber squeezer, rather than the disposable plastic things known as Pasteur pipettes now; the glass part was sterilizable or disposable
• the squeezer part is not intended to contain liquid, just air.  You press the squeezer, put the tip in the liquid and by releasing the squeezer you have a relative vaccuum sucking up the liquid; you dispense by pushing the squeezer again
• the marks on the stem part are there to indicate the volume dispensed
• when a drop can fall off freely, the size of it is determined by a)the outer diameter of the end of the tip, b) the surface tension of the liquid and c) the density of the liquid 
• Pasteur pipettes are mainly used to dispense in direct contact with some surface (filter paper, Petri plate or other), so drop size does not really matter.  The use as eye droppers is quantitatively less important.

[Karen W.]

You know.. as I read that it makes perfect sense and Neily was right about the tip.. I had wondered if thicker liquid would change the size of the drop but I thought nahhhh! LOL see what I know.. LOl when you said that about the air suddenly my brain went to thanksgiving dinner and using the turkey baster to suck up and push out liquid over the bird!... Nice job eric and neil!

[stefny]

Hello,
Nice post
sorry, i am new register for this site
so please guide me
Thanks

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