Well, while the mail continues to come in about my post yesterday, I’m going to pull back from the global perspective and zoom back into the glassware drawers of my lab bench today. A while back I wrote about the different sizes of ground glass joints that organic chemists typically use. People from outside the field are sometimes struck by the fact that we don’t have to do as much glassblowing and the like as they might have thought. Decades ago there was a lot more, but for a long time now we’ve been able to build up all sorts of apparatus (apparati?) by connecting standardized glass fittings together.
This has all sorts of advantages, letting us assemble odd custom configurations pretty easily, and change them without too much work. The downside is that the ground glass joints aren’t by themselves vacuum tight – not by the standards of inorganic chemists, for sure – and need to be anointed with thick, nasty vacuum grease before they can be trusted to that level. And if you don’t grease them for normal work, which we tend not to because the grease gets into your compounds, then the joints tend to freeze if left too long or too tight.
There are all sorts of voodoo tricks for unsticking them. I pride myself on being able to do it, but (objectively) I don’t think my success rate is all that greater than the norm. For the record, my technique is to put a few drops of silicon bath oil up around the edge of the stuck connection and let it soak in for a few hours. Then I rapidly heat the outside joint, grab it with a towel, and do the usual pulling and tapping while hoping for the best. There are better ways, but they're typically found only in a glassblowing shop.
When I last wrote about this fascinating subject (hey, chemists like their glassware), I mentioned that I’d gotten in the habit of using 29/42 size joints. (That’s a measure of size: the first number is a diameter, and the second is the length or taper). That’s a larger one than is common in American labs; you see it more in Germany, among other places. I’m so used to it now that the standard 24/40 glass joints you see all over the place look narrow and shrunken to me – will I really be able to get my product out of that?
The standard small size these days is 14/20 – that’s the size of all our 5, 10, and 25 milliter flasks. (You can get 100 mL flasks (or larger) with that size joint, too, but they start to look disproportionate and weird, and there’s no real reason for large flasks to have such a small neck). In between that and good ol’ 24/40, though is the 19/22 size, which I really should look at again. It would be the wide-mouth counterpart to 14/20, in the same way that 29/42 is to 24/40. I’d probably like it.
But I’ve hardly seen a flask of that size since I was an undergraduate, and that whole range of glassware immediately recalls sophomore organic chemistry labs. I wondered why that was, but now I have the story thanks to reader Norm Neill of glassmaker NDS Technologies, who saw its birth at Kontes:
"The 19/22 Glassware kit was developed jointly by Eric Nyberg from Kontes Glass and Dr Howard Martin from Lake Forest College in the late 1950's. . .they wanted to scale down the size of the glassware from the traditional 24/40 glassware to something smaller so it could be issued as a complete kit to a student and locked in his lab drawer. . .The next size down from 24/40 is 19/38 but the joint length was too long to allow us to scale down the kit (and) fit into a standard lab bench drawer. The 19/22 medium length joint was the best trade off at the time. . .The packaging of the kit was so popular that during the early 1960's production had to be allocated. The overwhelming success of the 19/22 glassware started the development of an extensive line of 14/20 glassware under the Bantamware® brand."
It's my impression that the 14/20 glassware has been taking over the student market in recent years as well, what with the move to smaller and smaller amounts of solvents and reagents. That makes me wonder if 19/22 glass has a future, which means that I'll probably find some lunatic reason to switch my small-scale stuff to it really soon, giving me the most oddball glass collection in the place. . .