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I plan to do some amateur chemistry with some basic equipment. I've watched hours of youtube videos for how to bend and polish glass tubing and push it through rubber stoppers, and I've seen diagrams of such tubing attached to rubber or silicone tubing, but nothing showing how to do that. I've even searched through catalogs of equipment and seen lots of specialized gadgets with hose barbs and such, but nothing basic. I just want to do a simple thing: have a rubber stopper with a glass tube in it, and attach that directly to a flexible tube. Nothing fancy, just one tube connected to another. I see it in diagrams like http://www.mctcteach.org/chemistry/C2224/labman/vacfilt/filter7.htm , but it gives no explanation. What am I missing?

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  • $\begingroup$ Why the downvote? Is this not a sincere question about lab procedure that's not answered by a Google search? $\endgroup$
    – Lee Daniel Crocker
    Commented May 4, 2018 at 20:46

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Heat up the soft tubing to make it easier to fit over the connection. Most labs have a heat gun that is used for this (amongst other uses). A hairdryer will serve, or put the end of the tubing in hot water. Many glass connection have what is called an olive which you have to push the tubing over while hot, when it cools it contracts giving a good seal (particularly important for the water lines of condensers which may be left overnight)

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    $\begingroup$ What "connection"? That's the whole of my question--plain glass tubing has no hose barb or anything like that. Am I supposed to just assume that the ID of the hose is a bit smaller than the OD of the glass? Do I attach a tube with an olive to the plain tube by melting them together? $\endgroup$
    – Lee Daniel Crocker
    Commented May 3, 2018 at 17:05
  • $\begingroup$ For plain glass with no olive I would try to choose soft tubing with a smaller internal diameter and soften it so that in can be pushed over (carefully) the glass tube. This is not that satisfactory but should hold if there's not too much pressure in the system. $\endgroup$
    – Waylander
    Commented May 3, 2018 at 17:55
  • $\begingroup$ That should work. It just seems odd that there are hundreds of different fittings for special applications, but not a simple one just for this. $\endgroup$
    – Lee Daniel Crocker
    Commented May 3, 2018 at 18:23
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You do this with great care, putting rubber or plastic tubing onto glass tubing or taking it off is a major cause of injuries in a chemistry lab.

I always saw that the most dangerous object in my lab is a traditional liebig condensor with short bits of glass tube which you push the plastic water hoses onto.

The best way to do it with rubber hoses (such as semipressure / vacuum hose) is to dip the end into dichloromethane or chloroform to make the rubber more soft, then to push the hose gently onto the glass tubing. To remove it, it if often best to cut the tubing off rather than pull it off if the tube will not come off with ease.

For plastic hoses such as PVC it is best to heat the plastic tube up with a hot air gun to make it more soft before trying to put it onto the glass tubing.

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