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Author: Subject: Handling toxic gasses in glassware

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[*] posted on 1-8-2018 at 06:36
Handling toxic gasses in glassware

Hello all,

A few days ago I proceded to make a small ammount of sulfuric acid by bubbling sulfur dioxide through hydrogen peroxide. It was moderatley sucsessful and shorlt I energetically begun to clean up by taking the stopper of the so2 genetator and got a decent wiff of the stuff. Luckily I was doing this outside so I stepped away for a few minuites and returned with a fan to blow away what was left.

TL;DR: I released sulfur dioxide gas and breathed a considerable ammount in.

Thinking back I suspect I should have flushed it out by puming some air into the generator and bubbling it through some NaOH for a few minuites but I wonder if this would truly solve the problem or would the SO2 simply settle to the bottom of the generator letting the air flow over due to the SO2's lower density.

Has anyone got any advice for toxic gasses in backyard lab settings?
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Hazard to Others

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[*] posted on 1-8-2018 at 07:44

A few weeks ago I made some nitric acid and I was left with glassware filled with NO2 that wouldn't disperse on its own through the openings. In order to clean this I took the whole apparatus to the tub, dissembled it and cleaned it with tap water while wearing thick neoprene gloves which went up to the elbow, safety goggles and a respirator suited for acidic gasses. Afterwards the bathroom smelled weakly of NO2 and in order to fix this I left an open bottle of household 10% NH3 in the bathroom and left the window open. After an hour there was no more smell of NO2.

During the actual distillation I used a sodium hydroxide trap to scrub the NO2 and the HNO3 exiting my apparatus. I constructed it as shown here in order to avoid suck-back: .

This kind of trap can be used for scrubbing many different gasses. For acidic gasses and halogens NaOH solution is good and for ammonia one should use an acid.

[Edited on 1-8-2018 by CobaltChloride]
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[*] posted on 1-8-2018 at 10:33

Consider building a portable gas scrubber like BromicAcid's.

There is a PDF around (I dont remember where I found it on the site) that diagrams disposal of waste gases into your sewer system. Maybe it was removed because it's not in keeping with best practices, but with proper scrubbing it's a nice way to avoid dealing with wind. As long as all your plumbing P-fixtures are intact. I'll attach the PDF later.

For very small scale, although I've not gotten much use out of mine, a gas trap or gas bubbler will do.

[Edited on 2-8-2018 by CouchHatter]

Attachment: apparatus for disposal of waste gases.pdf (114kB)
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[*] posted on 1-8-2018 at 15:44

Thankyou for the ideas.
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[*] posted on 1-8-2018 at 15:47

If you want some examples of good practice, I recommend UC235's YT channel. He has done a lot of interesting things in his garage and did not have a fume hood. His management of evolved gases in a safe manner is great.
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Dan Vizine
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[*] posted on 10-8-2018 at 10:43

If you're using glassware with well-greased ground glass joints and you have a reliable connection to a gas-tight tube connecting to the outside world you can make a lot of things safely, for example Br2 or HCN. If you're already in the outside world, the tube should simply terminate 20 or 30 feet away from you.

The power of dilution is potent protection and the amounts of incidental effluents (fumes above liquids, etc.) that you generate are statistically insignificant. Stoichiometric effluents, say a reaction generating a mole of HCl per mole of product produced, warrant an anti-suckback trap followed by a base trap (if they are large, anyway).

A respirator with activated charcoal filters is worth the price. It protects you from trace gasses that escape when the apparatus is eventually opened. Holding your breath for operations lasting less than 30 seconds should not be overlooked as a useful tool. For toxins not reliably adsorbed by charcoal, say HCN, this is quite effective. An amount of HCN sufficient to give you a "the lights are getting dimmer" feeling if breathed, will not even be noticeable after it has diffused into a few thousand cubic feet of air.

In professional labs, chemists often work in hood pans. These are SS pans, leakproof, with edges a few inches high. If a flask breaks it's nice to know that (once fumes abate) you can clean up a pan instead of replacing the floor. I use an enameled vegetable drawer from an old refrigerator. It's surprisingly resistant to most chemicals, even H2SO4 and similarly nasty materials.

Whether these practices constitute best practices is not really arguable. But, by definition, amateur labs aren't professional labs and what works sufficiently well to allow you to follow your passion without adverse effects to you or those around you is the real objective here. You can never totally eliminate risk, but you can manage it.

[Edited on 8/10/2018 by Dan Vizine]

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[*] posted on 10-8-2018 at 11:11

I've done the long tube trick a few times and have never had any problems with it, but it is a bit scary knowing that the room will be filled with toxic gases if you knock over the apparatus. I generally don't bother greasing the joints unless there will be a vacuum, but if you're handling anything super toxic or super flammable that can be a good idea. A fume hood is recommended. You will want to have a good respirator handy for sure. Make sure you have planned for the worst possible scenario (i.e. the apparatus getting knocked over and starting a fire as it dissolves the linoleum and fills the room with poison gas, setting off the fire alarm and bringing the police and your landlord to your house). If you're not prepared to deal with that, don't do the experiment.

I'm no longer involved in this forum.
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