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From: dwilkins@orion.polaristel.net (Don Wilkins)
Newsgroups: sci.chem
Subject: Re: How many drops =1ml
Date: Mon, 21 Oct 1996 00:12:29 GMT

On Sat, 19 Oct 1996 16:01:19 -0500, kleem chaudhary
<kchaudha@callisto.uwinnipeg.ca> wrote:


>On 19 Oct 1996, William Wu wrote:
>
>> kristo@minn.net wrote:
>> : About how many drops of water = 1ml?
>> 
>> **ABOUT** 20... of course it depends on the size of your drops. =P
>
>
>Unless you're doing analytical work, in which case you might want 
>half-drops!  There's a great philosophical question, is there such a 
>thing as half a drop?  I remember doing titrations in my analytical 
>chemistry lab and we were told to just use half-drops near the endpoint.  
>But can you really get half drops?  It becomes a drop in itself. 
>Comments?

20 drops is the number usually given in analytical work. Obviously
there can be some variation.

Half drops? No it doesn't become a drop in itself with proper
technique.

The technique when you approach an end point and want less than a drop
is to allow liquid to start to build up the drop size and when you
guess the size is appropriate turn off the stopcock and:

1. snap the burette with a finger to dislodge the liquid. (in this
case it becomes a drop).

2. Wash the  unfinished drop into the solution being titrated using a
wash bottle. (Questionable technique)

3. Touch a stirring rod to the unfinished drop and then wash the
titrant on the stirring rod into the solution using a wash bottle. (OK
if you use a dry stirring rod)

OK now for the quiz. When you pour the last of the wine into a glass
how many drops are left in the bottle?
Answer below:




With a little skill you can manage to count out 25 drops almost every
time. You will be able to do this enough times (with some practice) to
win consistently in barroom bets at your favorite pub. 

A little more than one cc gone to waste on every bottle.

 
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