Sciencemadness Discussion Board - Do you know chemicals by their smell?

Do you know chemicals by their smell?

Fyndium - 7-11-2020 at 17:28

This is obviously the most unhealthy way to determine anything that's not suitable for consumption, but generally speaking, can you instantly name what chemical is in question when you smell it? It doesn't help determine mixtures, of course, but for example toluene has such distinct smell and so low odor treshold that it cannot be undetected.

For almost every chemical I've handled, I've eventually had a chance to get a whiff of how they smell, and sometimes I've recognized a memory from a past and realized that I've smelt it before. One of things I haven't yet smelled is cyanide, and I don't know if there is a safe way to get to know it at all - I've taken very scrupulous safety measures when handling them.

paulll - 7-11-2020 at 17:53

Nile Red recently posted a video about smelling cyanide, if you haven't seen it.

karlos³ - 7-11-2020 at 18:49

Yes of course,
I can even sort a half dozen lachrymators

They don't even smell that bad, the first whiff at least, bromoketones in special are quite flowery

In general, I often try to get a little whiff when working the first time with something, made it, or received it, just out of curiosity.
Of course only for harmless substances.

Cou - 7-11-2020 at 21:11

I have a collection of about 20 esters and I could probably name which ester is it, if you blindfolded me and gave me the vial. They all have distinct aromas, except sec-butyl acetate and sec-butyl propionate are almost the same (solventy grapey smell)

in some cases the difference is subtle. Isopentyl acetate smells like artificially banana-flavored candies. Isopently propionate smells like actual banana fruits.

124263682_4071364626225805_1859281599500818606_o.jpg - 124kB

[Edited on 11-8-2020 by Cou]

Fluorite - 8-11-2020 at 00:04

Yas! I added sodium hydroxide to manganese dioxide from carbon zinc battery and immediately smelled the ammonia gas probably ammonium chloride is added as an electrolyte

I also can know the difference between hcl, chlorine, and chlorine dioxide just using my nose

Toluene, acetone, ethanol are pretty easy to detect and know which one is which of course some are pretty hard to differentiate like ethanol and methanol or dcm and chloroform

Ubya - 8-11-2020 at 07:18

well after a while you get used to the chemicals you use, like every girl can recognize the smell of acetone i can recognize the smell of methyl acetate in some paints (for example while working on the streets and a shop is being painted)
It is something that just comes natural with time

karlos³ - 8-11-2020 at 08:19

One smell I definitely don't want to get to know is the borane dimethylsulfide complex.
That must smell like the devils rectum

woelen - 8-11-2020 at 10:20

Quite a few chemicals I certainly recognize by smell:
- ammonia
- chlorine
- bromine
- nitrogen dioxide
- sulfur dioxide
- hydrogen sulfide
- phosphine
- acetone
- diethyl ether
- toluene

Some others are less distinct to me:
- HCl / HBr
- several organics
- HCN
- CrO2Cl2
- PCl5 / POCl3 / PCl3
- CCl4 / CHCl=CCl2 / CCl2=CCl2 / CHCl3 / CH3CCl3

Some chemicals I never smelled, even though I made them in small quantities. I just did my utmost best to not get any exposure to them:
- H2Se
- H2Te
- AsCl3

mackolol - 8-11-2020 at 12:57

I often get used to smells of chemicals I work with. For example heating not completely pure DMSO produces dimethyl sulfide which smells like sewers. First few times I just wanted to throw up, but now I can enjoy a while of peace from others, while sitting in lab full of the stuff

outer_limits - 8-11-2020 at 13:29

It's quite easy to recognize nitrogen oxide in exhaust fumes while walking near the road.
I had the pleasure to feel lovely smell of gaseous HCl, chlorine, bromine and multiple solvents in paint strippers etc.
Few days ago I noticed a strange ethereal smell in a place where it definitely shouldn't be used.

I also used to smell chemicals which I knew they wouldn't harm me. Sometimes it was a very bad decision which leaded to crying (as karl already mentioned).

Recently I am quite interested in very smelly organosulphur compounds which I plan to make (at least some of them). But of course on micro-scale, I don't want be a reason of my neighbourhood evacuation.

Fyndium - 8-11-2020 at 14:37

Once you smell phenylacetaldehyde, there's no unsmelling it when you walk past some flowers.

It's precursor styrene oxide has a more aromatic odor than styrene, a little towards the aldehyde. Phenylacetic acid apparently smells sort of pervasive mix of honey, mouse shit and flowers. The aldehyde oxidizes on it's own and I had the pleasure to have the smell laying around for few weeks after I had some waste to be processed. It's extremely tacky and I had a bag from the space which had the odor to it and it faded away only when I kept it outdoors several days.

Toluene reminds me of model crafting, boat making and just the general thinner smell.

H2O2 has faint but distinct odor. Good memories too. This happened almost 20 years ago, but I had an opportunity to smell the peroxide of acetone and I still remember it clearly.

Sulfuric acid has very faint smell too, but it can be carefully detected. Sulfur dioxide on the other hand, well, it will make sure you notice it.

Benzaldehyde, the bitter almond smell is one of the most pleasant odors I know.

Hydrogen bromide and ethyl bromide have a distinct smell.

Ethanol is not very smelly but it has many shades of smell. The very pure ethanolic smell to hand disinfectant and then the very low grade vodka.

Diethyl ether smell is actually pretty unpleasant to me. I always get to think that it's a nice thing to work with, but when I get it on work, it just starts to annoy you very quickly. Probably has to do with very low boiling point. Acetone is one of my favorite solvents because it's versatility and low toxicity and it smells sort of comfortable on small amounts but it very quickly hits the treshold when it starts to annoy.

Benzyl chloride, chloroacetone and those.. ew. No thanks. I don't like to work with them even in place where strong smells don't matter. They just need a mask.

Acetic acid is one of a PITA to work with. It tends to leak even from closed appratuses, and don't you think processing it in open vessels, especially hot and concentrated solutions.

I suppose I should test out cyanide as nilered did. Dissolving few mg amount in a volume of liquid and acidifying it a little would do the job without risk of poisoning.

I sort of like to get to know the odor profile of every chemical I work with - unless they are too toxic(which I practically haven't worked with yet), I feel like I know their properties better that way. The amounts you get when crossing the odor threshold are extremely minute and are likely to cause no harm in any extent. The really hazardous stuff I just left off, something like dioxins can be just excluded.

The odor of isocyanides and some of the worst smelling things fascinates me. Just how bad they smell to be the smelliest things? I might have a very slight hint, because burnt rubber, urethane and similar stuff gives off very annoying, unpleasant and sticky odor which is not bad in the sense people associate like fecal matter, but it's just very stingy, unnatural sort of.

woelen - 8-11-2020 at 23:59

I also smell most chemicals (carefully, low concentration, minute quantities), which I make or buy. Only very few chemicals I absolutely don't want to be exposed to, such as volatile arsenic compounds, mercury-compounds and a few organics. I indeed think that knowing the smell of chemicals makes you know their properties better and allows you to recognize them, also in unwanted/unexpected situations.

B(a)P - 9-11-2020 at 01:51

Quote: Originally posted by outer_limits

It's quite easy to recognize nitrogen oxide in exhaust fumes while walking near the road.
I had the pleasure to feel lovely smell of gaseous HCl, chlorine, bromine and multiple solvents in paint strippers etc.
Few days ago I noticed a strange ethereal smell in a place where it definitely shouldn't be used.

I also used to smell chemicals which I knew they wouldn't harm me. Sometimes it was a very bad decision which leaded to crying (as karl already mentioned).

Recently I am quite interested in very smelly organosulphur compounds which I plan to make (at least some of them). But of course on micro-scale, I don't want be a reason of my neighbourhood evacuation.

After my first runaway nitration, I then always noticed NOx in car exhaust.

[Edited on 9-11-2020 by B(a)P]

teodor - 9-11-2020 at 08:58

Do you like smell of sulfur compounds? This is funny:
https://blogs.sciencemag.org/pipeline/archives/2009/06/11/th...

"remember that, in a thioacetone situation, fogging the area with brown nitrogen oxide fumes will actually improve the air"

Quote: Originally posted by Fyndium

Ethanol is not very smelly but it has many shades of smell.

I've got your joke

But really I think that pure ethanol has less smell variances than chlorine and other halogens which can smell completely differently depending on concentrations and presence of different oxides.

Hot H2SO4 very often has smell of beet sugar. And I think it is really beet sugar has H2SO4 smell for some reason.

[Edited on 9-11-2020 by teodor]

karlos³ - 9-11-2020 at 10:03

Once I rode my bike and smelled pyrrolidine at a certain place... I had a little parcel with me containing 10ml of it though.
But on my way back without the parcel I could still smell pyrrolidine at the exact same place.
That was strange, and it was pyrrolidine, 100% sure about both points.

The smells you experience AND recognize as a chemist in everydays life

p4rtridg3 - 9-11-2020 at 10:27

Generally yes, once you get accustomed to certain chemical odors you can identify them pretty readily. Smells are hard to describe, but once you learn what a chemical smells like you won't forget it.

cyanureeves - 9-11-2020 at 10:53

some people smell bleach in semen and sour ass is identical in all men.i can identify the smell of battery acid which is just like almost every metal in sulfuric acid.the smell of chloroform is never forgotten either once you've smelt it.

[Edited on 11-9-2020 by cyanureeves]

cyanureeves - 9-11-2020 at 11:02

Quote: Originally posted by karlos³

Once I rode my bike and smelled pyrrolidine at a certain place... I had a little parcel with me containing 10ml of it though.
But on my way back without the parcel I could still smell pyrrolidine at the exact same place.
That was strange, and it was pyrrolidine, 100% sure about both points.

The smells you experience AND recognize as a chemist in everydays life

dude that had to be one of those things imprinted in your brain dont you think?you know like when sometimes you can smell burned rubber when watching cars peel out on tv.

Dr.Bob - 9-11-2020 at 12:33

I remember, many years back, being asked in a job interview "how to tell acetone from ethyl acetate?" and my first answer was "with one sniff", but I backed it up with IR, NMR, BP, density, ketone test with tosylhydrazine, and a few other simpe answers, and they offered me the job shortly later. There are still many chemicals that I can smell a mile away and identify, most bad like pyridine, benzyl chloroformate, and isonitriles, but I do also know some more pleasant ones like ether, amyl acetate (which as Cou noted smell like bananas), chloroform, and many others.

karlos³ - 9-11-2020 at 14:44

Quote: Originally posted by cyanureeves

dude that had to be one of those things imprinted in your brain dont you think?you know like when sometimes you can smell burned rubber when watching cars peel out on tv.

Definitely not, I stopped on the way back and wandered around sniffing(received weird looks of course

), but it appeared to came out of a block of flats nearby.
I was thinking someone close could have a lab too and was about decarboxylating proline or such?
I haven't even expected to notice the smell on my way back, but it hit me all of a sudden again.

Cou - 9-11-2020 at 17:22

Amyl acetate is not as pleasant as isoamyl acetate. Even small isomeric differences have an affect on odor, which is why I like aroma chemistry so much, there are countless possibilities from isomers alone.

Cou - 9-11-2020 at 22:21

the most annoying thing about short-chain carboxylic acids is their smell.
I can handle it while working with them. But I got 1 drop of isovaleric acid on the bathroom floor, and now I'm struck by the smell of dirty diaper every time I walk in.

teodor - 10-11-2020 at 00:41

Iso-butyric acid leaves nice after-smell, I can easily recognise it now in some cookies. The smell is described as "vomit" but practically it is much more like parmesan. So, never believe in descriptions, sniff by yourself

. But after Cou described difference in isomers I am wondering, has n-butyric the same smell as iso-butyric?

[Edited on 10-11-2020 by teodor]

ArbuzToWoda - 10-11-2020 at 00:44

Quote: Originally posted by teodor

Iso-butyric acid leaves nice after-smell, I can easily recognise it now in some cookies. The smell is described as "vomit" but practically it is much more like parmesan. So, never believe in descriptions, sniff by yourself

. But after Cou described difference in isomers I am wondering, has n-butyric the same smell as iso-butyric?

[Edited on 10-11-2020 by teodor]

In my experience no, the smell of n-butyric acid is putrid and unbearable in higher concentrations. It really does smell like spoiled butter.

outer_limits - 10-11-2020 at 01:14

Quote: Originally posted by Cou

the most annoying thing about short-chain carboxylic acids is their smell.
I can handle it while working with them. But I got 1 drop of isovaleric acid on the bathroom floor, and now I'm struck by the smell of dirty diaper every time I walk in.

I love the smell of butyric acid in the morning...

teodor - 10-11-2020 at 01:28

I noticed some very nice unusual smell when prepared K[Sb(OH)6]. Also I noticed that type of smell second time when was working with antimony. I still don't know is it antimony compound itself or same organic impurity in the starting material which gives a byproduct with such smell.

woelen - 10-11-2020 at 01:57

If the two occurrences of the smell are with completely different SB-compounds, then there is a good chance that it really is some Sb-compound. I myself have done quite a few experiments with SB, Sb2O3 and Sb2S3, but I never noticed a special smell. The only thing I smelled was the smell of rotten eggs, when experimenting with Sb2S3 and acids

teodor - 10-11-2020 at 03:23

I just used the same Sb2O3 from a pottery shop as a starting material for all my experiments with antimony so it is quite possible there is some impurity in it.

I have a packet of lichens in may laboratory, on a heater, this small quantity produces the dominant smell in my lab. It's amazing how strong this smell is - and it always smells in very low concentration (I have a jam bottle with 25% ammonia and lichens inside, but I couldn't feel ammonia smell when the bottle is closed, only the smell of lichens). It's similar to mushrooms, very-very pleasant.

[Edited on 10-11-2020 by teodor]

[Edited on 10-11-2020 by teodor]

MidLifeChemist - 10-11-2020 at 08:07

Wow, I continue to be impressed by your knowledge of chemistry. Kudos to you for becoming familiar with so many different chemicals in a safe manner. It will be a while before I'm comfortable working with many of those gases, but I'm sure I'll get there, and I can always start off with micro-quantities.

Btw, Hydrogen selenide looks particularly nasty and dangerous, based on the safety data sheets - much more so than H2S or HCN. But on the other hand, I read on the CDC website that our bodies quickly decompose it into elemental red selenium, so I'm not sure where exactly to place it on the list of deadly gases.

Btw, I noticed that HF was not on your list

Quote: Originally posted by woelen

Quite a few chemicals I certainly recognize by smell:
- ammonia
- chlorine
- bromine
- nitrogen dioxide
- sulfur dioxide
- hydrogen sulfide
- phosphine
- acetone
- diethyl ether
- toluene

Some others are less distinct to me:
- HCl / HBr
- several organics
- HCN
- CrO2Cl2
- PCl5 / POCl3 / PCl3
- CCl4 / CHCl=CCl2 / CCl2=CCl2 / CHCl3 / CH3CCl3

Some chemicals I never smelled, even though I made them in small quantities. I just did my utmost best to not get any exposure to them:
- H2Se
- H2Te
- AsCl3

itsallgoodjames - 10-11-2020 at 10:08

By smell, I can identify the following:
-NO2 (I've probably smelled far too much of this one)
-NH3
-Cl2
-I2
-SO2
-H2S
-HCl
-HCN

And for organics:
-Chloroform
-Acetone
-Toluene
-A handful of acetate esters
-A handful of primary and secondary alcohols
-Glacial acetic acid

That's more than half the organics I have. I have way more inorganic compounds than that, so if I recall something else I'll add it

[Edited on 10-11-2020 by itsallgoodjames]

[Edited on 10-11-2020 by itsallgoodjames]

Cou - 10-11-2020 at 22:22

Quote: Originally posted by teodor

. But after Cou described difference in isomers I am wondering, has n-butyric the same smell as iso-butyric?

[Edited on 10-11-2020 by teodor]

butyric acid is much more vile and biley.
isobutyric acid is more sour, vinegar-y

TriiodideFrog - 11-11-2020 at 01:11

There are many chemicals but some have very distinct smells. Sotolon (Sotolone) is a lactone and an extremely powerful aroma compound, with the smell of fenugreek or curry at high concentrations and maple syrup, caramel, or burnt sugar at lower concentrations. However, some chemicals smell almost the same and the fumes are poisonous. I would strongly not recommend you to expose yourself to too many chemical fumes.

karlos³ - 11-11-2020 at 08:36

Sotolone sounds tasty!
There was an accidental release of four kilo in a chemical factory which evaporated after coming in contact with a hot surface, and in the whole location of the cities cologne and düsseldorf it could be smelled

Soupy, maggi, lovage smell, that must have been heavenly tasty and appetizing!

nezza - 15-11-2020 at 11:59

I too have a selection of esters which all smell pleasant and are pretty non toxic.
I have worked with both some mercaptans and pyridine.
2 mercaptoethanol is revolting and penetrating and minute amounts stink the place out.
Pyridine is just vile. Ammoniacal and nasty.
One reagent which I used at work to make buffers was Barbitone (Sodium diethylbarbiturate). A solid but it did have a faint pleasant smell and nice sweetish taste (In very small amounts).
Woelen says he has never smelled H2Se. I did synthesise some and took a cautious sniff. Bad move.
I really can't describe the smell because it paralysed my sense of smell almost instantly. A faint hint of H2S possibly before my nose switched off.
It took the best part of a day to recover my sense of smell. Very unpleasant and not to be recommended.

Syn the Sizer - 15-11-2020 at 13:44

Quote: Originally posted by karlos³

In general, I often try to get a little whiff when working the first time with something, made it, or received it, just out of curiosity.
Of course only for harmless substances.

I too do this, I believe it is good to be familiar with the smell of something you are working with, you can tell either whether the reaction is working by either detecting new smell, or if the reaction is familiar, a familiar smell of the product.

As well you can detect if a spill has happened in your lab and if you should run and call Hazmat or venture in and clean it yourself.

[Edited on 15-11-2020 by Syn the Sizer]