RU_KLO
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The odour of death...
In qualitative chemistry some preliminary test are smell test. This is by heating or by adding acid (mostly HCl) and identifying the odor (if any)
Probably most here know/can differentiate SO2, NOx, CN-, H2S odors, and other toxic fumes from (bad) experience.
I know that there are lethal (poision) gases, and some are more than others. (can read ppm LC/LD from wiki, althoug cannot meassure them or imagine
how much is it)
Also know that one should not smell direclty, but by moving the vapors with the hand.
The question is, in order to learn/identify the smells, how much substance is dangerous to use in a test tube for making the poisonous gases?
For example 5mg of Iron Sulfide in 10ml HCl (20%) is enough to learn the smell (H2S)? Will it kill me or give me some bad effect?
Same as potassium ferricyanide 5mg + 10 ml HCl (20%) -> HCN
I dont want to kill myself, but you cannot learn the smell from youtube or books....
Go SAFE, because stupidity and bad Luck exist.
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Admagistr
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The problem with some of these compounds is that only their safe,or relatively safe concentrations are smelled,an example would be H2S,at lethal
concentrations the olfactory nerve is immediately paralyzed,so one doesn't smell the typical rotten egg smell at all and soon dies...It could also be
HCN,or other compounds on your list,but I don't know,it would be interesting if a toxicology expert could answer that...
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RU_KLO
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After searching found something similar (of course I dont want to make/sniff war gases), but HCN, Phosgene, Chlorine, Sulfide, Bromine and others are
more or less common in Chemitry.
https://commons.wikimedia.org/wiki/File:Smelling_Case_of_War...
Go SAFE, because stupidity and bad Luck exist.
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B(a)P
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A crude way of doing this would be to use immediately dangerous to life and health (IDLH) values. I am not saying this is an approach that will ensure
your safety, just an approach to give you an idea about what industry thinks is safe.
A good and reliable source for this data is the CDC, though each jurisdiction will typically develop their own. The CDC includes a lot of information
about the basis for the exposure limits that can help you decide what is safe for you.
The IDLH will typically be for an exposure of duration greater than one sniff, often up to an hour, so there is some conservatism there.
If you want to be still more conservative you could look for a value that below which no health effect is likely over an 8 hour working day like the
recommended exposure limit (REL) design for the protection of health in the occupational environment. You could also opt for the short term exposure
limit (STEL) this is the same as the TWA, but for 15 minutes. You need to decide what you feel comfortable with in therms of IDLH, TWA or STEL. Think
about how often you do olfactory assessments of chemicals, if you do it often for a longish duration consider the TWA or STEL, if it is a few times a
year maybe the IDLH is more appropriate.
So let us take Cl2, it has an IDLH of 30 ppm, roughly 90 mg/m3. If the reaction in your test tube produces something close to 90
mg of chlorine you may be getting close to your IDLH. If your reaction produces significantly less that 90 mg of chlorine, you are unlikely to exceed
the IDLH.
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woelen
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One way to stay safe is to lookup total dangerous doses for certain compounds and making these compounds in much smaller quantities.
E.g. a compound like HCN has a lethal dose of 50 mg totally absorbed amount into the body for a grown up person of average weight. With less than 5 mg
there are no lasting adverse effects. So, you could take 5 mg of ferrocyanide and heat that with a little dilute H2SO4 (not HCl, because that has a
smell of its own) and waft the gas from the test tube to your nose. This is absolutely safe. In practice, you do not inhale 5 mg, because
1) 5 mg of ferrocyanide salt gives less than 5 mg of HCN;
2) most of the gas is dispersed into the air, you only inhale a fraction of it;
3) part of the gas remains in the aquous solution.
The risk of this way of working is that you don't smell anything at all, because concentrations remain too low. But that is better than risking severe
health effects ;-).
For many gases, things can be done safely in an easier way.
1) Work outside, so that no gas can build up in a closed room.
2) Only use a small pinch of solid material (a few mm pile of solid on the tip of a screw driver)
3) Waft gases to your nose, do not stick you nose in the test tube.
Some tests:
1) Mix 1 ml bleach and 2 ml dilute HCl for smelling Cl2
2) Mix a spatula full of KBr (or NaBr), 2 ml of dilute HCl and 1 ml bleach for smelling Br2
3) Add 2 ml of dilute H2SO4 or HCl to a little FeS or Na2S for smelling H2S
4) Add a little NaNO2 to dilute H2SO4 for smelling NO/NO2
5) Add a few thin wires of copper to 1 ml of conc. HNO3 for smelling NO/NO2
6) Add a little NaNO2 to conc. HCl for smelling ONCl
7) Add a little NaClO2 to 25% HCl for smelling ClO2 (differs quite a lot from Cl2)
8) Add a little Na2SO3 or NaHSO3 to dilute H2SO4 for smelling SO2
9) Smell household ammonia (3% to 5%) carefully from its bottle for smelling NH3.
With HCN, be more careful, appr. 1/3 of all people cannot smell that.
This kind of tests can be done easily and are safe, provided you do not do these tests too often. An occasional whiff of these gases is no problem,
but of course you must use common sense. Do not do many of this kind of tests in a row. Doing two or three of these tests after each other on a single
day, however, is not a problem.
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j_sum1
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I have never smelled HCN. It would be good to know if I have this ability. Might be a little experiment for the weekend.
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woelen
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Be careful, you are too valuable for sciencemadness 
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j_sum1
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Of course I will be careful.
Or maybe not.
Being careful is when I have had my most dramatic accidents.
Seriously though. I will follow your guideline -- making a quantity so small such that even if I ingested all of it, it would be insufficient to
cause harm.
And it would be a good thing to know if I was one of those people incapable of smelling HCN.
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j_sum1
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I am moving this from Beginnings to Responsible Practices since it deals with safety concerns and how to acquire experience and practical knowledge of
dangerous gases.
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j_sum1
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Thread Moved
8-6-2023 at 00:50 |
unionised
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Quote: Originally posted by j_sum1  | | I have never smelled HCN. It would be good to know if I have this ability. Might be a little experiment for the weekend. |
Why?
Nobody should ever be in a position of relying on "it's OK, I will smell it before it kills me".
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Admagistr
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| Quote: Originally posted by unionised | | Quote: Originally posted by j_sum1 | | I have never smelled HCN. It would be good to know if I have this ability. Might be a little experiment for the weekend. |
Why?
Nobody should ever be in a position of relying on "it's OK, I will smell it before it kills me". |
You are absolutely right, as I wrote above, high and instantly fatal concentrations of some poisons paralyze the olfactory nerve and the person feels
nothing at all and dies instantly!
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teodor
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In old books I like to read places like "CrO3 has a bit acrid taste which will disappead on chewing" or "Ba(BF3)2 has a taste which is quite similar
with taste of other barium salts".
But, I think, usage of a nose is much safer for analytical work 
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Admagistr
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And who would be willing to taste the beautifully sweet taste of beryllium salts)? I don't think I would personally go for it...
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B(a)P
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| Quote: Originally posted by unionised | | Quote: Originally posted by j_sum1 | | I have never smelled HCN. It would be good to know if I have this ability. Might be a little experiment for the weekend. |
Why?
Nobody should ever be in a position of relying on "it's OK, I will smell it before it kills me". |
This is not quite true. I work in the assessment and clean up of contaminated land. If we are working with a contaminant that has an odour threshold
well below the health based exposure limit then an effective control to determine if your respirator cartridges need replacing is when you can first
smell the contaminant. Obviously this does not work/or is not appropriate for all contaminants, you need to know what you are working with and its
toxicological profile.
In my home lab when I am working with a new compound I will check to see if its odour threshold is below its exposure limit. If it is not, I will
employ different controls when experimenting with it, than I otherwise would have.
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Rainwater
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| Quote: Originally posted by B(a)P |
If we are working with a contaminant that has an odour threshold well below the health based exposure limit then an effective control to determine if
your respirator cartridges need replacing is when you can first smell the contaminant. |
We do the same at work, they also provide strip that resemble ph paper that stick to the outlet of the filter on your mask because some people cant
smell some gasses.
Test strips
mask
Filters are cheap to. The organic vapor ones are great. Face full of ether and dcm for 15-20 minutes before needing a swap. Low level exposure, once a
day or until you catch a wiff
Just to add to the conversation, please dont be that dumbass, remimber what curiosity did to that cat.
If you want to safely smell some things
NO, NO2 work on a NG waterheater
SO2 - walk past a peace of idling construction equipment burning off road diesel
Dont go full metal jacket and try suckstarting anything more dangerous than that, the number of brain cells in this world has not increased in many
years despite the boom in population.
"You can't do that" - challenge accepted
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j_sum1
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Well, thanks for the concern. I have no intention of doing anything stupid.
But, if I can gain some knowledge safely, what's the problem?
Specifically, what is the issue with the scheme presented by RU_KLO?
| Quote: | | potassium ferricyanide 5mg + 10 ml HCl (20%) -> HCN |
(Granted I have not double-checked the quantities, but I will. And scale down if necessary.)
As to why... There are I think a bunch of good reasons.
Curiosity is sufficient reason by itself. Obviously not combined with reckless stupidity. But with the risks reduced to negligible levels, I am not
seeing a problem.
Gaining experience is another good reason. I can draw from my knowledge of H2S to explain.
I have spent a lot of time in a city where there is a lot of naturally-occurring H2S from geothermal sources. Levels are often well above the odour
threshold but never reach the levels where they can cause harm.
So, I know what it smells like and am not freaked out by it. I also know that I have never experienced levels sufficient to deaden the olfactory
nerves. And I know that I can't personally do any serious experimentation with H2S until I get my fume hood (which is a project that always seems to
be pushed back, but that is another story.)
I know enough to recognise it and to assess the risks of a procedure. I know that smell recognition is insufficient as a safety protocol. And I know
enough to not panic if I catch a whiff of something when I open a container of Na2S.
Likewise, I have experienced SO2, NO2, Cl2, Br2, NH3. And I2 come to think of it. Being able to recognise HCN would not be stupid. Alternatively,
discovering that I was one of those individuals who cannot detect it would seem to me to be useful information.
Then there is the ability to respond on those occasions when things do not go to plan. I have been in a couple of situations when the appropriate
response was to drop and run. The most recent was when an ampoule of bromine smashed. I held my breath and evacuated. If I smell HCN when it is
unexpected then I want to be able to deploy the running shoes and then figure out what the hell has happened. That is a whole lot better than staying
in place and thinking, "that's a weird smell".
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Tsjerk
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As woelen said, use sulfuric acid instead of HCl, as that has an odour itself.
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B(a)P
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| Quote: Originally posted by j_sum1 | Well, thanks for the concern. I have no intention of doing anything stupid.
But, if I can gain some knowledge safely, what's the problem?
Specifically, what is the issue with the scheme presented by RU_KLO?
| Quote: | | potassium ferricyanide 5mg + 10 ml HCl (20%) -> HCN |
(Granted I have not double-checked the quantities, but I will. And scale down if necessary.)
|
It has been reported that 45 to 54 ppm can be tolerated for 0.5 to 1 hour without immediate or delayed effects while 110 to 135 ppm may be fatal after
0.5 to 1 hour or later, or dangerous to life (Flury F, Zernik F [1931]. Schädliche gase dämpfe, nebel, rauch- und staubarten. Berlin, Germany:
Verlag von Julius Springer, p. 404)
The odour threshold for HCN varies between individuals, approximately 2 to 10 ppm. Using 5 mg may not be enough starting material to generate
sufficient HCN to detect it. That will only get you about 2 to 2.5 ppm if the HCN is generated all at once and concentrated within your breathing
space. Do check these numbers before you embark on this yourself, I have just estimated what I have written down here. I look forward to hearing how
you go!
Edit
I just remembered that Nile Red did this, which you may find interesting and or useful.
[Edited on 9-6-2023 by B(a)P]
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j_sum1
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Yeah. I remember that. Cody did something similar.
I am not going to get to the lab this weekend anyway. The flood of marking has arrived.
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Herr Haber
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After "discovering" PH3 and HN3 in two disctinct events by accident the initiative seems reasonable.
In both cases I was able to understand what had happened and therefore the nature of the gases in moments. The amounts were tiny so I never was in any
danger.
I never whiffed HCN but assumed from litterature it would be more "interesting" than HN3 unless I cant smell it. Hence the lasting curiosity.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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SplendidAcylation
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This reminds me of an accident I had a few years back; It really is an example of all the dumb things you shouldn't do as a chemist!
Luckily I survived with seemingly no harm done...
I had just acquired some TCCA, and I wanted to test that it was the right thing, so I placed a spatula-tip of powdered TCCA in a tiny glass jar and
added ~1mL of hydrochloric acid, whereupon I closed the lid loosely.
I observed considerable effervescence, and the inside of the jar quickly became green-tinged with chlorine.
Satisfied, I closed the lid of the jar, and left the jar, filled with visibly-green chlorine gas, lying around on a shelf...
A few days later I made a pleasant smelling compound (I don't remember which, maybe chlorobutanol, or some ester), I placed this new compound in an
identical glass jar, on the same shelf...
A few hours later, I was doing a write-up on the preparation of the compound, and I decided to see what it smelled like, so I could describe the
pleasant smell more accurately.
I went to the shelf, picked up the jar, removed the lid, and took a long, deep sniff of this wonderful ester I had created... Only to find I had
picked up the wrong jar.
Fairly instantly I knew something was amiss, as I experienced a short-lived pain in my nose and sinuses.
I had no idea what had happened, as I couldn't smell anything; I couldn't stop coughing and gagging, it was very difficult to breathe simply due to
the constant coughing, by this point there was little or no pain, but instantly my eyes were watering and my nose was totally congested, like having a
cold.
After a minute of constant coughing and choking, I was able to regain some sort of composure, however there was no smell of chlorine at any point,
obviously the concentration was way too high and overwhelmed by olfactory senses or something.
The next hour or two was characterized by frequent coughing, a very congested nose, and a fairly mild sore-throat, with difficulty swallowing.
I had no sense of taste or smell at this point really...
A few hours later, I had mostly recovered and I went to bed.
The next day I was almost fully recovered, with no lasting after-effects.
Overall, sniffing maybe 10mL of fairly pure chlorine gas was a very unpleasant experience, and not one I would recommend!
That said, it really allowed me to understand the horrors of war...
Dulce Et Decorum Est indeed...
[Edited on 3-7-2023 by SplendidAcylation]
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leau
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HCN
As Gattermann states in his very fine textbook, smoking tobacco will sensitize most people to the odour of HCN eventually  Tobacco smoking is known to cause many different health issues such as lung cancer
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j_sum1
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| Quote: Originally posted by leau | | As Gattermann states in his very fine textbook, smoking tobacco will sensitize most people to the odour of HCN eventually Tobacco smoking is known to cause many different health issues such as lung cancer
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Not a good enough reason to take up smoking.
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SplendidAcylation
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| Quote: Originally posted by j_sum1 | | Quote: Originally posted by leau | | As Gattermann states in his very fine textbook, smoking tobacco will sensitize most people to the odour of HCN eventually Tobacco smoking is known to cause many different health issues such as lung cancer
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Not a good enough reason to take up smoking. |
It can help you detect phosgene apparently, resulting in an unpleasant taste when smoking, if there is phosgene in the air.
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