InFormation
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Registered: 2-12-2010
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Flask Neck Size
Stupid questions -
I brought myself some nice glassware this week, but the stoppers recommended by the suppliers are a terrible fit to my new flasks. I ordered #11s for
my 250mL Erlenmeyers (advertised 32mm neck), and #12s for my 500mL Erlenmeyer (advertised 37mm neck).
Almost all of them don't even fit.
At first I thought the recommended stoppers must have been advertised wrong, but then I measured the necks of my flasks:
1. 250mL - 26mm neck.
2. 250mL - 29mm neck.
3. 500mL - 28mm neck.
My #11s fit flask 2 (one of the 250mL's) perfectly, and some of them in the 3rd flask. My #12's only fit my 500mL when jammed in, corner by corner.
Flask 1 accepts none of the stoppers I purchased.
All this in mind, I was wondering:
1). Do flasks normally have such differences in neck size?
2). Do stoppers get less stiff after a while and fit better?
3). How far down the neck is a stopper supposed to go? - at the moment, on flask 2, they only reach about 3-4mm down the neck.
[Edited on 11-12-2010 by InFormation]
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psychokinetic
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Depending on how they are made, yeah there are often differences. However, if number 3 was advertised as 37mm and is really 28, you might want to get
your complaining hat on.
2: Not in my experience... I find they get stiffer. I think that's a humidity and environment variable.
3: Until it blocks everything.
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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InFormation
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Thanks for that mate. It's just bugging me that I buy stoppers to suit, and none of them actually fit, except for to one of my 250mL conicals. They
also gave me 10 #5's instead of 10 #4's, and none of them actually fit my test tubes. Also, instead of the 500mL beaker I ordered, I was given a 400mL
with a round bottom - won't sit straight. Oh, and did I mention that I was only given the nipples for the three pipettes I ordered? 
Should I argue the 250mL conicals since the necks are so different that the advertised stoppers won't fit one of them, or is this commonplace? Just
want to make sure I'm not overreacting with naivety before I make a formal complaint.
EDIT: I re-measured the flasks, and it turns out the diameter is in fact including the outside of the neck, not just the inner
diameter. They are within a couple of millimeters as advertised, so my bad. Still doesn't change that the advertised stoppers don't fit, I'll just buy
some of a smaller size. Thanks for the help all the same.
[Edited on 12-12-2010 by InFormation]
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aonomus
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All of my glassware is Kimble or Pyrex, and specify the stopper number on the flasks (wrt Erlenmeyers only). I don't see variation in sizes at all
really. Sometimes I see wide(r) necked flasks at work, but they are all pretty standard.
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