TLutman
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Posts: 26
Registered: 13-10-2019
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Acid problems
Just looking for some opinions on what happened with a couple distillations of acid.
First was liquid fire drain cleaner. I took it outside with a 500ml flask, 300mm condenser w/o water, a vacuum adapter and a 500ml beaker. Things went
like normal with moderate bumping. After 100ml or so, I would get violent ejections of dense vapor and acid. Definitely cleared out the condenser. The
largest was 10cu ft or better .
This was probably at the beginning of the concentrated H₂SO₄ coming over, as the condensate appeared noticeably more viscous.
Problem, or does it happen?
Next was a run of HNO₃ last night. I had 400g KNO₃, 200ml H₂O, and 230ml H₂SO₄.
This was done in a 3neck 1000ml flask, 300mm condenser w/ water, gas adapter with a 3/8 hose which went up to the inlet of my exhaust fan, and a
500ml receiving flask.
Things went as expected for the majority. I had a thermocouple well in the still head and changed flasks around 115C. I had about 250ml distilled,
and the boiling flask was still a see through amber color with no foam on top. I looked up at a monitor I have on the top of my fumehood (maybe
10sec) when I heard a loud pop and see a big steam cloud in front of me, still contained within the hood. I jumped up, turned the exhaust to hi,
turned off the heat and lowered the mantle, then surveyed the damage.
I had the boiling flask turned so the ports were front to back. I charged from the front, still head in the vertical, and a stopper in the rear. I
put clips on all joints except the rear port, just in case. Yep, it paid off. The best I figure is the sulfate crashed out in just those few seconds
and a large burst of steam. No sulfate reached the top of the flask or beyond, but was ejected out the rear port all over the back and top of the
fumehood. Looked like someone flung wet instant potatoes everywhere. The last temp I saw was 121C, just a few secs before. The vent tube was not
plugged, but couldn’t handle that instantaneous pressure anyhow. The boiling flask was wrapped with foil to the still head.
Any thoughts ?
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CharlieA
National Hazard
Posts: 646
Registered: 11-8-2015
Location: Missouri, USA
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Some random thoughts: heating too rapidly? no anti-bumping provisions, g. boiling stones? an ebulliator tube (these can work for distillations at
atmospheric P, not just distillations at reduced-P)?
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TLutman
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Posts: 26
Registered: 13-10-2019
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Heating too fast? I thought I was being conservative on it, but I will try slowing it down a bit. I have more dilute nitric acid than I would have
liked after distilling. I basically followed a dougs lab video, and perhaps will give it another go with half the water if I need to make more. It’s
easier to add water than take it out.
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