cnidocyte
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Informing oneself about highly toxic gases commonly encountered by the home chemist
Can anyone recommend a good website or article to start with? I looked through this wiki page
http://en.wikipedia.org/wiki/List_of_highly_toxic_gases
and was surprised that NO2 wasn't on that list. I heard bad things about NO2 on threads on SM and other forums and assumed it was one of the more
lethal gases one may encounter in a home lab. Thought it was worse than H2S. Heres another list
http://www.ehs.berkeley.edu/healthsafety/toxicgasprogram/com...
but they none of these lists explain how a home chemist might produce dangerous quantities of these lethal gases and ways to avoid this. Anyone know a
site or article that does?
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peach
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There are basically so many possible ways to produce these gases that all of us, combined, couldn't produce a half complete list.
You need to look at the reaction you're running, work out what's coming off, then think about how to scrub or filter it.
It is a common saying from people talking about risk management, you can't deal with a risk until you can identify the risk.
This is what makes, in my opinion, gases like carbon monoxide so much more scary than corrosive gases. As soon as the tiniest amount of corrosive gas
escapes my glassware, I can smell it, I can taste it, I can feel it on my eyes, it stings like a skewer up my nose and I'll involuntarily cough if I
take a deep enough breath. I can even see it, fuming.
Within a second, I've spotted it and can check all the tapers are seated (which is usually the issue, one's come a little loose).
Monoxide, on the other hand, the 'silent killer', you can't smell, feel or otherwise sense. Once it's working on you, you'll only notice it (and I use
the word 'notice' in a very loose sense, as you probably won't) when your ability to think and operate blurs, making it a snowballing problem (it's
getting harder for you to work out what's happening and how to fix it). People being poisoned by CO usually drift off still sat in the chair with
their mug of tea in their hand.
Add to that, active carbon scrubbers in fume hoods can't scrub CO. Neither can a number of respirator filters based on active carbon alone.
H2S is (from memory) the second leading cause of death in industry, behind fire. It's also not 'toxic' in the way sublimating mercury salts would be.
In that, provided you're removed from the contamination in time, you can be flopped out on the floor and come round fine, suffering no long lasting
damage. It's even being put into clinical trials as a form of dropping metastasis into a hibernation like pattern in critically injured patients as
they're moved from a roadside to a theater. Hopefully you can see from that, how it's not so clear cut.
In summary, this is really something you need to have a think about yourself. Dealing with it is quite a personal thing, and others can only give you
pointers when you bring up a specific reaction (you'll usually get "that'll produce ...." and maybe "run it through an upturned funnel in water").
Beyond that, it's often down to you. Attempting to cover it all in a general discussion will never work.
I take the attitude that, if you have a respirator and hazmat on, you've probably fucked up.
[Edited on 14-8-2010 by peach]
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BromicAcid
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I agree completely. As a home chemist it is always our responsibility to ensure the safety of those around us. Wearing a resperator or hazmat
protects you but not the others although it's always good to have these things on hand as a safety precaution and you should not preclude your own
safety. It's just not something you should have on so as to be able to do things with impunity.
Regarding a list of poison gasses, I have a very comprehensive one somewhere on my hard drive... amongst the book project stuff that I never got to
updating. Sure there are plenty of highly toxic compounds, but amongst those compounds that are gasses at STP there are considerably less and
subtract those compounds that the chemist at home would not 'stumble across' then the list gets much shorter.
The problem with any essential list is that it needs to be memorized, not kept as a reference. These are things you should know off the top of your
head, things like, "Hummm... better not mix that sulfide with acid..." or "What's this gas? Am I oxidizing my alcohol all the way to CO2? No... but
my chloroform wouldn't oxidize would it?"
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cnidocyte
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Thanks for the info. I do research every reaction I think about performing of course, its just I have trouble guaging the hazards of particular gases
by reading the MSDS. For example I wanted to try burning some sulfur yesterday, so I looked up the MSDS of SO2 but couldn't really determine how
dangerous SO2 gas is. Its not a healthy gas to inhale so I suppose the best approach is to make sure you don't even inhale a single ppm of the stuff.
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DDTea
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cnidocyte: you may want to research OSHA exposure limits for the toxic gasses you're interested in. MSDS's are great for people who are constantly
working with a substance, but their information doesn't apply as well to people who only come across a substance occasionally. Pay special attention
to the alerting properties of gasses or the concentrations at which they can be smelled (IF they can be smelled). Also, find out if they're heavier
than air or lighter than air or visible or invisible.
But as others have said, if you're even exposing yourself to toxic fumes, you're doing something wrong.
"In the end the proud scientist or philosopher who cannot be bothered to make his thought accessible has no choice but to retire to the heights in
which dwell the Great Misunderstood and the Great Ignored, there to rail in Olympic superiority at the folly of mankind." - Reginald Kapp.
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peach
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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]
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cnidocyte
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DDTea: OSHA exposure limits thats exactly what I was looking for, thanks.
peach: Highly informative post, nice one. Hate grapefruit juice myself too. When I was a kid I used to love making "potions" which would consist of
just about everything I could find under the kitchen sink (thank god nobody bought ammonia cuz there was always bleach in there) and one day my mom
found one of them, opened it up to smell it and 1 whiff of it had her on the phone to the poison hotline. She said she felt her throat burning, got
dizzy and went temporarily blind.
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. Heres an article on this
http://www.nature.com/news/2006/061211/full/news061211-18.ht...
I see what you mean about irritating properties being a plus for the chemist. 2 acids I've got a whiff of that gave me a fright are conc. HCl and my
attempt at making GAA in the freezer. Both times I got a strong smell and mild burning sensation in my nasal cavity which gave me enough of a fright
to ensure I didn't inhale any more. 1 gas I'm well informed about from working on oil rigs is H2S. The stuff stinks but its when you stop smelling it
that you're in trouble since it disables the sense of smell when you've inhaled a certain amount of it. Smell is a sense I've always greatly
undervalued, thinking about all this makes me reevaluate it.
The stuff mentioned in peach's posts is exactly the reason I started this thread. Mercury is a toxin we've all heard about and most of us have an idea
of its insidious nature but I didn't put CO in my list of compounds to be weary of before reading this thread. A highly insidious gas. A quick
question though: what is scrubbing? Heard the term plenty of times but couldn't find anything googling it.
[Edited on 15-8-2010 by cnidocyte]
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peach
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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]
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cnidocyte
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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]
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peach
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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.
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The WiZard is In
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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. |
The nose is definitely one of the chemists best friends.
Or worst enemy. The problem is called accommodation you
become use to an odour and do not notice when it gets stronger.
This from an ad from Voronez.
At first sight it seems that nature has provided for protection from
the harmful gas. A human nose is able to catch hydrogen sulphide
(according to the manual’s definition, the substance that strongly
reeks) in absolutely tiny quantities when the gas concentration in
the air is expressed in the thousandths of milligram per cubic
meter. But the paradox is that this particular sensitivity of the
nose can let us down: when the hydrogen sulphide concentration is
approaching the maximum allowable value impending chronic
disease of respiratory tract, blood, eyes, skin and digestive
apparatus, the smell seems weaker to us. This is a kind of
olfactory illusion.
-------
When 244 persons were tested, 12% (29) could not smell hydrogen cyanide.
And off the 88% (214) that could 25% (53) could make the
determination only with difficulty. [5]
[5] Kirk RL Stenhouse NS: Ability to smell solutions of
potassium cyanide.
Nature 171:698-99, 1953
[109] Carmelo, S: [New contributions to the study of subacute-
chronic hydrocyanic acid intoxication’s in man.] Rass Med nd 24:254-71, 1955 (Ita)
In:—
NISOH Criteria for a recommended standard…….
Occupational exposure to Hydrogen Cyanide and Cyanide Salts
(NaCN, KCN and Ca(CN)2 US Dept of HEW
October 1976
A reference to cigar smoking as an aid in detecting cyanide.
Gattermann, Ann. 357, 318 (1907)
(Cited in: Organic Syntheses Collective Volume I. Pg. 315)
As other have mentioned OSHA &c, exposure limits are 'bout
useless as most of us have no way of measuring the concentration
of the gases we are working.
The best fume cupboard in a strong wind while working out of doors.
djh
-----
Experimental science doesn't
have to be a dying art.
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White Yeti
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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
"Ja, Kalzium, das ist alles!" -Otto Loewi
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