starman
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American/British glassware compatible?
Just seeking a clarificaion on the sizing nomenclature.
24/40 seems most common grnd glass sizing in the states.
Surely thats not the taper of the joint?(Compare our 24/29.)
Is it inside/outside wall?
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Ramiel
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\/\/\/ got corrected later in the thread. Good to know when you're wrong! 
I've never seen a 24/29 in any lab in WA, so I must guess that 24/40 is the accepted standard here in .au
19/24 is very common though, it seems to be popular for smaller scale work (it is incompatible with the 24/** stuff for obvious reasons!)
[Edited on 3-8-2008 by Ramiel]
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-jeffB
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I believe 24 is the top diameter in mm, and 40 is the length of the joint; I think the angles are identical, so they're compatible in some
circumstances. I hope someone who has both can step in to verify this.
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matei
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jeffB is right. We have a rotavap that has a 24/40 joint and we are using it with 24/29 glassware.
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not_important
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Seconding that. The ST symbol on some ground joints stands for "standard taper", the taper slope of the joint is the same on all ST joints; the first
number is the width at the base/tip of the joint while the second number is the length of the tapered section.
http://en.wikipedia.org/wiki/Ground_glass_joint
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starman
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Thanks for clearing that up for me guys.
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DJF90
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The taper is actually 10 degrees IIRC. Is the length of the taper the actual length, or the height (eg is it the hypotenuse or the adjacent (for those
who do trigonometry  ))
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unionised
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The taper isn't 10 degrees, it's 1 in 10. I'm not sure how they measure the "length" but it doesn't matter much.
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DJF90
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Ah ok, my mistake 
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Magpie
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I have been searching for a replacement plug for a stopcock on an antiquated Kontes pressure equalization funnel. I bought the funnel on eBay, as
advertized, without the plug. The price was right and I figured I could easily buy a replacement plug.
Since all my other stopcocks have Teflon plugs (sep funnels, burets, etc) I naturally assumed this is what I should get. But I could see that the
funnel stopcock body taper wasn't right for a Teflon plug. It seems that, in the US at least, the Teflon plugs are 1:5 taper (PS), whereas the glass
plug stopcocks are standard taper (ST), 1:10. So I have concluded, after much measuring and computing, that I just need to buy the glass plug, and
that that is what the funnel must have had orginally.
Also I have concluded that taper is determined by subtracting the small diameter of the bore from the large diameter of the bore, then dividing this
by the length of the bore. For example, for a 24/40 (ST), the bore length would be 40mm, the large diameter 24mm, and the small diameter 20mm. This
can be checked as:
(24-20)/40 = 0.1, or 1:10
I really have not read any official method for determining taper for glassware from measurements. This is just my conclusion. If anyone else has
some more authoritative information or different opinions I would be interested to hear them.
It is interesting to note that when I talked to a technical person at Kontes she wasn't aware of my method for determining taper. She said that the
plug is just specified by the plug crossbore (2mm) and a number like 11/25, where the 11 is the diameter of the plug in mm at the center of the plug,
and the 25 is the plug length in mm. But it seems to me that the first thing you have to know is if the plug is 1:5 (PS) or 1:10 (ST).
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S.C. Wack
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Note that Coyne, the best single reference for etc. labware info that I know of, says that some Teflon stopcocks were 1:7. He does not elaborate any
further on those, except that they are gone.
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watson.fawkes
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The Pegasus Glass lampworking blanks catalog lists PTFE stopcocks in both 1:7.5 and 1:5 tapers and glass in 1:10.
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bfesser
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The tech at Kontes was right. Is there any number printed on the glass stopcock joint? What's the joint size on the bottom of the funnel?
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Magpie
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| Quote: |
The tech at Kontes was right. Is there any number printed on the glass stopcock joint? What's the joint size on the bottom of the funnel?
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Oh I agree that the tech was right - as far as that goes. But her specifications don't give you the taper. Or are you sayng that it is not needed?
There is a designation of "2-A" at the joint.
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bfesser
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I have two Kontes standard taper 14/20 50 mL pressure-equalized addition funnels (one graduated, one not). Both of the stopcock joints are marked 2-A
[Crown]. They take 10/25 glass stopcocks with a 1:10 taper and a 2 mm bore.
If you have a pair of callipers, very carefully take the following three measurements (be careful not to scratch or crack the inside of the joint).
Inside diameter on the narrow end.
Inside diameter on the wide end.
Length across the joint.
(I can take pictures of the way to measure length across the joint later, if needed.)
[Edited on 12/3/08 by bfesser]
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Magpie
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| Quote: |
I have two Kontes standard taper 14/20 50 mL pressure-equalized addition funnels (one graduated, one not). Both of the stopcock joints are marked 2-A
[Crown]. They take 11/25 glass stopcocks with a 1:10 taper and a 2 mm bore.
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My Kontes pressure-equalization graduated funnel is of 125 ml capacity and has a 19/22 fill opening.
I don't have inside calipers that will reach the center, just the cone ends. I measured the conical bore length to be 25mm, the large opening of the
cone to be ~11mm, and that of the small opening of the cone to be ~9mm. I therefore conclude that the center diameter is ~10mm.
Looking at the Kontes on-line catalogue, I can't find this particular funnel and assume it is no longer available. But they do offer item
305751-0221, which is a glass plug of standard taper (ST), 2 mm crossbore, and designated 10/25. This is what I was planning on buying.
[Edited on 3-12-2008 by Magpie]
[Edited on 3-12-2008 by Magpie]
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bfesser
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Yes, that plug should do the trick. If you're ordering from Kontes directly, they have a $50 minimum order. I haven't ordered from them, but would
like to in the future if possible. Please let us know what you think of them.
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Magpie
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Because of the $50 minimum I was planning to buy the plug from VWR. By entering the Kontes number in the VWR search I pulled up the Kontes plug.
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