Sciencemadness Discussion Board - Help with lecture bottles?

Help with lecture bottles?

numos - 19-4-2020 at 16:39

I've worked with lecture bottles before, and I have this beautiful bottle of NO2 that by tare, is completely full. I can hear it sloshing around inside as well. The problem is the valve is jammed. Really a bummer because it looks so new and shiny. Unscrewing the black handle, you can see the mechanism is basically 3 parts - the valve, the hex nut thing, and the square nut. The handle turns the square nut. That part turns fine - very smoothly opens and closes, but no gas comes out. Opening the hex nut or main valve body will probably cause a total gas release....

Any ideas what to do here or on the workings of these valves? Since NO2 has such a low vapor pressure, I could stick it in the freezer to liquefy and try to quickly replace the valve with a new identical one. Ideally I'd be able to fix this valve, but might be trickey.

wg48temp9 - 19-4-2020 at 18:12

It looks like a packless valve. Perhaps lower stem is corroded or jammed so it can not move. You could try tapping the valve in its open position to attempt loosen the lower stem.

BromicAcid - 19-4-2020 at 18:34

Isn't there an 800-number on the lecture bottle? Might be worth giving it a ring since it is the manufacturer's packaging that failed.

Boffis - 19-4-2020 at 21:48

If the NO2 is pure then it boils at 21 C so that if the bottle is cooler than this the internal pressure will be less than atmospheric pressure so the liquid will remain liquid and inside the bottle! You will need to warm the bottle up to >22 C to get anything out of it.

numos - 19-4-2020 at 22:16

I thought it was a temperature thing as well, but heating it to 40C had no effect. It should have a substantial vapor pressure at that point.

I called them before and it was a Sigma representative. They said they could send me a new one if I have the original purchase order. Also I doubt they would send a replacement to a private address!

The packless valve design look spot on. Any idea why they design it like that? Seems kinda crappy to not have the valve directly connected to the handle, it seems obvious a jam like this could happen... I'll probably cool this to to 0C and try to get the valve unstuck mechanically.

wg48temp9 - 20-4-2020 at 00:38

Quote: Originally posted by numos

The packless valve design look spot on. Any idea why they design it like that? Seems kinda crappy to not have the valve directly connected to the handle, it seems obvious a jam like this could happen... I'll probably cool this to to 0C and try to get the valve unstuck mechanically.

With metal diaphragm sealing the gas from the control handle stem it is less likely to leak than a packed stem so its safer.