Informing oneself about highly toxic gases commonly encountered by the home chemist

Quote: Originally posted by peach

I take the attitude that, if you have a respirator and hazmat on, you've probably fucked up.

DDTea is correct, and I would have posted the same suggestions if he'd left it at OSHA limits. A key factor (as he says) is knowing at what concentrations you can smell it at. If it's below the dangerous levels, that's good. Far below, even better. You also need to know what kind of danger it presents at those levels (simple irritant, asphixiant, carcinogenic, mutagen, tetragen, neurotoxic, liver damage, temporary effect, long term accumulator, et cetera).

The same is true of flammable materials, knowing how they would boil at a certain temperature (their vapour pressure), the temperature at which they'll form an ignitable mixture of the atmosphere (flash point) and the temperature at which they'll ignite without an ignition source present (autoignition). Propane, for instance, won't ignite if there's not a few percent of it in the mixture. The cylinder companies purposefully add mercaptan to odourless gas to make it stink below those concentrations, so you'll smell it before it becomes a fire / explosion risk; mercaptan stinks in very low concentrations. Something a lot of people don't realise is that even very flammable gases become 'inert' with regards to fires when the concentration gets very high, because there's no longer enough oxygen in the mixture for it to burn.

The 'stenchant' or 'stenching agent' is detectable down to 0.002ppm.

People who make dish soaps do something similar. In the UK, we have 'Stardrops', an ammonia based washing up liquid. They add bitrex to it which, if you've ever tasted some of it, tastes absolutely foul. I believe it's actually the most potent flavour humans can taste, and it tastes horribly bitter. By adding a small amount to the soap, they're making it taste disgusting to kid who might drink it by mistake. My mum managed to drink some at one point (don't know if they'd added the bitrex by then) thinking it was grapefruit juice. Can't stand grapefruits myself! They taste like bitrex to me, maybe that's how she managed to drink it.

There are some chemicals some people can't taste because they don't have the receptors for that molecule. In secondary school (high school) we all had a taste of phenylthiocarbamide laced strips of paper to look at how the genetics of that behaves. Some people look like they've got a wasp in their mouth, other's can't taste anything at all. It's a very clear cut, dramatic difference between "YUCK!" and "tastes like paper...".

Bitrex is also used to test things like respirators industrially. The person puts the mask on, someone puts a hood over their head and they spray puffs of bitrex into the hood. If the seals are leaking, with such a high concentration of bitrex in the hood, they'll taste it no problems. Tastes unbearably nasty even at 10ppm.

Carbon Monoxide, something most people think of as a kind of wussy toxin, can't be spotted by chemical detectors (I think) until it reach around 5ppm. 50ppm is the safe exposure threshold (I think) and 300ppm will kill you in an hour or two (with a number of us spending 6 hours or more working on our reactions).

SO2 belongs to my 'not too difficult and very obvious' categorization method. At 0.5ppm, you'll smell it. At 20ppm, it'll be stinging and burning. 100ppm will start burning your respiratory tract; so you'll be involuntarily coughing with every breath.

What is key is that the gas is not 'toxic' in the way CO is, it's severely irritating and can burn your mucous membranes at very high concentrations and exposure durations, but it's not entering your body and messing with your DNA, liver, kidneys, brain or heart in any significant manner. If you leave the room and go out into the fresh air, you'll be fine.

Conversely, CO will mess with your brain and it will mess with the oxygen balance in your bloodstream. The lack of oxygen carrying capacity will knock you out. The gas is also 'neurotoxic' in that it can cause delusional behavior or even forms of temporary psychosis in large amounts. Coupled with it having zero odor and it's potential to kill you, that's far worse than SO2 in my opinion.

Equally, you have things like mercury salts, that are solids you can easily see. But they still have vapour pressures, so they are emitting vapours at room temperature. Warm them slightly (in a reaction for example), and it's worse. Breath the undetectable fumes in and they'll begin 'rotting' your brain by stalling axon / dendrite growth cones, permanently. It's also very difficult to remove from the body, and will accumulate over each exposure.

In your example of SO2, dealing with that wouldn't be hard at all. SO2 happily dissolves in water to produce sulphurous acid. So, right away you have a method of absorbing it by piping the exhaust of the reaction through a bit of tube or pipette poking to the base of a beaker full of cold water.

And I expect you know that acids tend to react with bases. So, adding a little base to the wash water will encourage it to stay in the water and scrub out of the stream even more effectively.

The same is true of things like HCl(g). It readily dissolves in water to produce hydrochloric acid. Add base to the water and it'll convert to soluble salt, dragging it out of the gas stream trying to get through. If you water is near saturated KOH, that gas isn't going anywhere fast.

[Edited on 15-8-2010 by peach]

I used to do that as a kid as well, along with taking apart anything electrical that didn't feature security bolts (triangles etc), and I'd still have a go at those with the mole grips, resulting in numerous 240V shocks before the age of 10. For anyone else who enjoys that sensation, and is all grown up, here's a porn site made specially for kinky social deviants and 'preverts' like you and I (18+, and wrong in the head)

I also used to make my own super detergents by mixing together whatever I could find under the sink. One of these released what I now believe was chlorine gas. It stank the room out to the extent that I had to leave and had a headache. But I reasoned, if it stinks that much, it must be really good. The innocent ignorance of youth. And before anyone comments on how that is akin to my just posted response on sulphuric acid burns, I was about 7 at the time and still learning to read, not 47; hence the rest of the label usually suggesting "keep out of sight and reach of children".

I do think the sense of smell dogs and cats have is somewhat biased by a few factors. First of all, my cats continually lick their noses, to keep them damp. Which improves the gas absorption on the surface (which is where they also have receptors, I think). Secondly, they don't 'smell' things in that sense, they touch their nose against it. I suspect, in that sense, it's more like they're tasting the scent.

With regards to them licking their nose and face all the time, try offering your cat some soup with chilli in it. Almost as funny as sticky tape on the paws ("flying cat") or printer label on the bonce ("crouch mode cat"). And before anyone reports me to the RSPCA, they're from the RSPCA and routinely get fed bits of my dinner at the table, then turn their noses up at my premium chicken or salmon, or get fed before I make my own dinner.

John

[Edited on 15-8-2010 by peach]

lol never seen a cats reaction to chilli but one day I was camping in the forest in Canada and my dog ran after something and when she came back she was dragging her face off the grass and rolling around like an epileptic on crack. It was a skunk she ran after. Lucky there was a river nearby but even after swimming the dog stank for weeks. I remember the smell well since my dog was spoilt and had to sleep in the tent with us lol. What a bizarre smell. A combination of these

after a few days you get used to it.

[Edited on 15-8-2010 by cnidocyte]

Nothing funnier than a dog or cat dragging it's ass along the floor. I almost wet myself when one of ours did that for the first time.

Along the lines of the 'what chemicals smell nice' thread, I'd also like to make things like mercaptan and the rotting body aromas, if only to see if I throw up upon smelling them and just how strong and repulsive they are in pure forms. I'm intrepidly guessing, they're bad. Possibly, very bad.

Quote: Originally posted by cnidocyte

I saw a documentary about an Israeli scientist who trained students to follow scent trailts like sniffer dogs and it worked. His argument for humans having extremely potent sense of smell was the fact you can dissolve a nanogram (or something I dont remember the details) of a certain extremely smelly compound in a swimming pool and we will still be able to smell it despite the fact it is dissolved in a whole swimming pool. The nose is definitely one of the chemists best friends. That documentary was an episode of Weird Connections.

Interesting thread.

As for toxic gases and such, I personally do reactions that involve these gases outside, NEVER under a fume hood. I've dealt with H2S before, and I gotta tell you, a paralysed sense of smell is not pleasant. I tried to eat something while my sense of smell was knocked out (making lemonade out of lemons) and food tastes awful when your sense of smell doesn't work. Sulphur dioxide is another nasty one many people overlook, if you have lung problems, this stuff will mess up your lungs big time.

Other than those, the standard NO2, NO, O3, Cl2, I2, CO, Br2, PH3, HCN etc... should be handled outside if you're an amateur. If you have a fumehood strong enough to create a small tornado, then you should be fine. I think the biggest danger comes from overlooking the hazards associated with these gases.

If you want to know how to make these gases:
NOx are produced when nitric acid reacts with copper, or when a nitrate salt is thermally decomposed.
Ozone is created when two electrodes with a high potential difference are brought together and no spark is allowed to jump between them.
Halogens are made when you displace any other halogen (except fluorine) by passing chlorine gas through a solution of a metal halide.
CO is made when organic matter is heated in the absence of oxygen.
Phosphine is made when hypophosphites are decomposed.
Hydrogen cyanide is made by treating a cyanide salt with acid.

Now you can render your neighbourhood uninhabitable