12 ms·

Why can we smell copper?

125 points by Alupis 6y ago

FlyMoreRockets 6y ago
You can't smell copper. The smell associated with copper is from a chemical known as 1-octen-3-one, which is generated when your skin oils react with metal that you've touched. NileRed does a good job explaining this. https://www.youtube.com/watch?v=BqLH-nTZEOc https://www.youtube.com/watch?v=BqLH-nTZEOc
- smt88 6y ago
  That is exactly what the linked post says, and it also does a good job explaining this.
  - jeromenerf 6y ago
    Reddit, Wikipedia and a multitude of other forums have this stereotype superuser person capable of super answers. I guess this was the motivation to share this url on HN, the smell of metals, of the snow or the rain mystery should have been solved for all in school no ?
- systemvoltage 6y ago
  I love the smell of tooling steel! As nasty as it sounds, it is quite special and reminds me of the good times in the shop.
  - h4tch 6y ago
    Have you ever smelt (sic) maple syrup when it heats up while chipping away at it? Maybe it was a combination of steel and the coolant.
- raducu 6y ago
  You can also smell iron in this way?
- IncRnd 6y ago
  There is more to the article than the headline.
- fuzzfactor 6y ago
  It is an interesting phenomenon when you can smell solid iron or copper just by touching it. I guess direct contact is as close as you can get to the metal. But most of the time I'd rather not touch it. Interestingly, with the molten stuff I get the same smell the closer I come to it, within a number of feet rather than inches or direct contact. And I know there's plenty of the element in its gaseous state vaporizing from the melt so it makes perfect sense. No organic compounds necessary. Or could be they are already in or near your nose to begin with. Once a molecule of metal like this does evaporate into the atmosphere it is extremely unlikely to ever become solid unoxidized metal again. Most naked metal atoms are easily oxidized by air to their positively-charged ionic form, which in its gaseous state highly diluted by the same air can still exist as a gas for quite some time and distance before settling out due to its relatively heavier molecular weight compared to air. Unless the concentration of gaseous metal is above a certain amount, there will be no conventional precipitation of the solid metal oxide from the air, instead each molecule of oxide will remain in its gaseous form as long as possible until it settles individually without ever combining or crystallizing with any of its own kind. No need for the gaseous metal to remain above its actual boiling point according to its characteristic phase behavior. Once the metal's not in its pure form the phase behavior diagram for that element does not apply any more. >Immediately after skin-metal contact, the SPME fiber collected volatile compounds for 5 minutes. The SPME samples were analyzed by GC/MS (Agilent GC column DB-5, 30 m x 250 μm x 0.3 μm, GC 6890, MS 5973, 115in EI mode, Environmental Chemstation G1701CA) We've got one of these instruments, they are great for detecting and identifying volatile organic compounds, and it looks like theirs was expertly operated in a research way. On the GC/MS the Gas Chromatograph separates the sample mixture into its individual components (according to controlled volatility), which are then detected by the Mass Spectrometer as each component gradually emerges from the chromatograph, traditionally forming a series of peaks on a chart. The spectrometer works to reveal the chemical identity of each peak, relying on a vast library of known references. In addition their parallel olfactory work puts an outstanding dimension on GC data not usually seen in many labs. This is where you run a tube directly from the exit of the chromatograph up to your nose to smell each peak as it emerges. The spectrometer can only tell you so much. Lots of instruments basically amplify the senses, but the senses can still be pretty good on their own. This was developed not just for fragrance research, interestingly there are some volatile chemicals that can be more reliably detected in super-small concentrations by nose than by established electronics. The SPME is Solid-Phase Micro-Extraction, a technique where sample components found in very low trace quantities are concentrated for better detection above the same instrument baseline, compared to direct chromatography of the plain sample. It really does combine to show excellent progress on skin-borne compounds' volatile organic reaction products. I would want to further experiment by taking a similar approach using the ICP/MS to detect the exact metal concentration in the same air samples as were being exposed to SPME. The ICP/MS units are built to measure trace metals, the GC/MS for trace volatile organics. They even have GC/ICP/MS which they used for the phosphorus- and arsenic-based volatile compounds, I would like to see if there was any detection of iron itself, which if it made it through the chromatograph to the ICP/MS it would be an organic form. In the machine shop I figure gaseous metal is being generated through friction even under coolant without any actual melting. No matter how small the proportion of individual metal molecules that make it into the atmosphere without being a member of an actual particle, once they are there they are not coming down right away and it will be relative to their distance from the source. There is also the possibility that free metal molecules or ions rapidly form interesting organometallic complexes with some organic materials on the hands, and complexes like that can have orders-of-magnitude more vapor pressure compared to the raw metal. Even though the complex has the metal carrying around a small carbon attachment adding to its molecular weight, there are forces that could cause a molecule of the complex to travel through the air further than the plain metal or oxide would once emitted from the source.
filleokus 6y ago
Probably not as unknown, but the smell in pools that I've always associated with chlorine is in fact the smell of some product when chlorine react with urine. I wonder what other falsehoods I believe along the same lines. I'm sure there are plenty in the realm of software/hardware. On the other hand, is there any difference between this kind of misconception and others? I feel there is. The observed correlation is very strong, and the wrong causal relationship is made based on assumptions that are extremely common. We sniff a thing, and what we sense is what we call that thing's smell. But again, this is probably a wrong conclusion very often (depending on how you want to define a "thing's smell"). If I smell a book, is it actually the book that smells or some kind of organic thing that grows on the paper? Is it meaningful to separate the two? </saturday morning philosophizing> 0: https://waterandhealth.org/healthy-pools/busting-chlorine-swimming-pool-urban-myth/ https://waterandhealth.org/healthy-pools/busting-chlorine-sw...
- coldtea 6y ago
  >Probably not as unknown, but the smell in pools that I've always associated with chlorine is in fact the smell of some product when chlorine react with urine. Chlorine does have a smell, and fresh pools do smell (where nobody has entered, much less, urinated in them yet). From the linked article itself: "A healthy chlorinated pool can emit a light chemical odor, especially if it is an indoor pool and one with less than ideal ventilation". The most common smell once people enter a pool is from chloramines from other kind of pollutants (body oils, etc) not urine. If it gets to urination you get much stronger smells. But the smell you've associated with chlorine is 99% chlorine derivatives, present in any chlorinated pool, i.e. the "chemical odor" mentioned in the article.
  - flignats 6y ago
    nope, Mark Rober did a video on this. It's urine and sweat.
    - deleted 6y ago
      [deleted]
    - 6y ago
ojosilva 6y ago
So does that mean these steel inox "soap bars" for getting the (cooking) smells off your hands actually work? I told my girlfriend that they did not work... But maybe I was wrong, the OP talks about the catalytic effect of some metals reacting with the oils in your hand or food traces.
- qlm 6y ago
  They've always worked for me. I was pretty surprised that rubbing a bit of metal was more effective than soap at getting smells off my hands.
- ZeljkoS 6y ago
  From https://en.wikipedia.org/wiki/Stainless_steel_soap https://en.wikipedia.org/wiki/Stainless_steel_soap: "The aim of the stainless steel soap is to then bind to the sulfur molecules, thus removing them and the associated smell from the hands. However, scientific evidence of the efficacy of these soaps appears lacking."
- askvictor 6y ago
  Yep, they work. You can also use a spoon.
- yosamino 6y ago
  I cut garlic with my chef's knive, for the added benefit of being able to use the large blade area of the knive to wash my hands with afterwards. Works really well to get the smell off and "I wash myself with a knive" has a pretty good ring to it.
  - raverbashing 6y ago
    I wonder what kind of degradation this might have over the sink metal (probably very minor, still...)
- refurb 6y ago
  Yes they work. As a chemist, sulfur compounds tend to bind quite tightly with metals. We actually have to look out for this with metal catalysts, as trace sulfur impurities can kill a reaction. It’s called “poisoning” which gives you an idea how tightly they bind.
2Gkashmiri 6y ago
sniff sniff I love the smell of petrol. Hmmm
andrelaszlo 6y ago
The Youtuber NileRed made a video about this. He explains why there are certain smells associated with metals and then makes some pure 1-octen-3-one in his lab. Very interesting! https://youtu.be/BqLH-nTZEOc https://youtu.be/BqLH-nTZEOc
- Triv888 6y ago
  It's a good video but I wonder if anyone ever made a large quantity of 1-octen-3-one using oil and metal instead (or whatever is from the skin...). It seems like it could be simpler.

125 points by Alupis 6y ago

You can't smell copper. The smell associated with copper is from a chemical known as 1-octen-3-one, which is generated when your skin oils react with metal that you've touched. NileRed does a good job explaining this. https://www.youtube.com/watch?v=BqLH-nTZEOc https://www.youtube.com/watch?v=BqLH-nTZEOc

smt88 6y ago
That is exactly what the linked post says, and it also does a good job explaining this.
- jeromenerf 6y ago
  Reddit, Wikipedia and a multitude of other forums have this stereotype superuser person capable of super answers. I guess this was the motivation to share this url on HN, the smell of metals, of the snow or the rain mystery should have been solved for all in school no ?
systemvoltage 6y ago
I love the smell of tooling steel! As nasty as it sounds, it is quite special and reminds me of the good times in the shop.
- h4tch 6y ago
  Have you ever smelt (sic) maple syrup when it heats up while chipping away at it? Maybe it was a combination of steel and the coolant.
raducu 6y ago
You can also smell iron in this way?
IncRnd 6y ago
There is more to the article than the headline.
fuzzfactor 6y ago
It is an interesting phenomenon when you can smell solid iron or copper just by touching it. I guess direct contact is as close as you can get to the metal. But most of the time I'd rather not touch it. Interestingly, with the molten stuff I get the same smell the closer I come to it, within a number of feet rather than inches or direct contact. And I know there's plenty of the element in its gaseous state vaporizing from the melt so it makes perfect sense. No organic compounds necessary. Or could be they are already in or near your nose to begin with. Once a molecule of metal like this does evaporate into the atmosphere it is extremely unlikely to ever become solid unoxidized metal again. Most naked metal atoms are easily oxidized by air to their positively-charged ionic form, which in its gaseous state highly diluted by the same air can still exist as a gas for quite some time and distance before settling out due to its relatively heavier molecular weight compared to air. Unless the concentration of gaseous metal is above a certain amount, there will be no conventional precipitation of the solid metal oxide from the air, instead each molecule of oxide will remain in its gaseous form as long as possible until it settles individually without ever combining or crystallizing with any of its own kind. No need for the gaseous metal to remain above its actual boiling point according to its characteristic phase behavior. Once the metal's not in its pure form the phase behavior diagram for that element does not apply any more. >Immediately after skin-metal contact, the SPME fiber collected volatile compounds for 5 minutes. The SPME samples were analyzed by GC/MS (Agilent GC column DB-5, 30 m x 250 μm x 0.3 μm, GC 6890, MS 5973, 115in EI mode, Environmental Chemstation G1701CA) We've got one of these instruments, they are great for detecting and identifying volatile organic compounds, and it looks like theirs was expertly operated in a research way. On the GC/MS the Gas Chromatograph separates the sample mixture into its individual components (according to controlled volatility), which are then detected by the Mass Spectrometer as each component gradually emerges from the chromatograph, traditionally forming a series of peaks on a chart. The spectrometer works to reveal the chemical identity of each peak, relying on a vast library of known references. In addition their parallel olfactory work puts an outstanding dimension on GC data not usually seen in many labs. This is where you run a tube directly from the exit of the chromatograph up to your nose to smell each peak as it emerges. The spectrometer can only tell you so much. Lots of instruments basically amplify the senses, but the senses can still be pretty good on their own. This was developed not just for fragrance research, interestingly there are some volatile chemicals that can be more reliably detected in super-small concentrations by nose than by established electronics. The SPME is Solid-Phase Micro-Extraction, a technique where sample components found in very low trace quantities are concentrated for better detection above the same instrument baseline, compared to direct chromatography of the plain sample. It really does combine to show excellent progress on skin-borne compounds' volatile organic reaction products. I would want to further experiment by taking a similar approach using the ICP/MS to detect the exact metal concentration in the same air samples as were being exposed to SPME. The ICP/MS units are built to measure trace metals, the GC/MS for trace volatile organics. They even have GC/ICP/MS which they used for the phosphorus- and arsenic-based volatile compounds, I would like to see if there was any detection of iron itself, which if it made it through the chromatograph to the ICP/MS it would be an organic form. In the machine shop I figure gaseous metal is being generated through friction even under coolant without any actual melting. No matter how small the proportion of individual metal molecules that make it into the atmosphere without being a member of an actual particle, once they are there they are not coming down right away and it will be relative to their distance from the source. There is also the possibility that free metal molecules or ions rapidly form interesting organometallic complexes with some organic materials on the hands, and complexes like that can have orders-of-magnitude more vapor pressure compared to the raw metal. Even though the complex has the metal carrying around a small carbon attachment adding to its molecular weight, there are forces that could cause a molecule of the complex to travel through the air further than the plain metal or oxide would once emitted from the source.

filleokus 6y ago

Probably not as unknown, but the smell in pools that I've always associated with chlorine is in fact the smell of some product when chlorine react with urine. I wonder what other falsehoods I believe along the same lines. I'm sure there are plenty in the realm of software/hardware. On the other hand, is there any difference between this kind of misconception and others? I feel there is. The observed correlation is very strong, and the wrong causal relationship is made based on assumptions that are extremely common. We sniff a thing, and what we sense is what we call that thing's smell. But again, this is probably a wrong conclusion very often (depending on how you want to define a "thing's smell"). If I smell a book, is it actually the book that smells or some kind of organic thing that grows on the paper? Is it meaningful to separate the two? </saturday morning philosophizing> 0: https://waterandhealth.org/healthy-pools/busting-chlorine-swimming-pool-urban-myth/ https://waterandhealth.org/healthy-pools/busting-chlorine-sw...

coldtea 6y ago
>Probably not as unknown, but the smell in pools that I've always associated with chlorine is in fact the smell of some product when chlorine react with urine. Chlorine does have a smell, and fresh pools do smell (where nobody has entered, much less, urinated in them yet). From the linked article itself: "A healthy chlorinated pool can emit a light chemical odor, especially if it is an indoor pool and one with less than ideal ventilation". The most common smell once people enter a pool is from chloramines from other kind of pollutants (body oils, etc) not urine. If it gets to urination you get much stronger smells. But the smell you've associated with chlorine is 99% chlorine derivatives, present in any chlorinated pool, i.e. the "chemical odor" mentioned in the article.
- flignats 6y ago
  nope, Mark Rober did a video on this. It's urine and sweat.
  - deleted 6y ago
    [deleted]
  - 6y ago

ojosilva 6y ago

So does that mean these steel inox "soap bars" for getting the (cooking) smells off your hands actually work? I told my girlfriend that they did not work... But maybe I was wrong, the OP talks about the catalytic effect of some metals reacting with the oils in your hand or food traces.

qlm 6y ago
They've always worked for me. I was pretty surprised that rubbing a bit of metal was more effective than soap at getting smells off my hands.
ZeljkoS 6y ago
From https://en.wikipedia.org/wiki/Stainless_steel_soap https://en.wikipedia.org/wiki/Stainless_steel_soap: "The aim of the stainless steel soap is to then bind to the sulfur molecules, thus removing them and the associated smell from the hands. However, scientific evidence of the efficacy of these soaps appears lacking."
askvictor 6y ago
Yep, they work. You can also use a spoon.
yosamino 6y ago
I cut garlic with my chef's knive, for the added benefit of being able to use the large blade area of the knive to wash my hands with afterwards. Works really well to get the smell off and "I wash myself with a knive" has a pretty good ring to it.
- raverbashing 6y ago
  I wonder what kind of degradation this might have over the sink metal (probably very minor, still...)
refurb 6y ago
Yes they work. As a chemist, sulfur compounds tend to bind quite tightly with metals. We actually have to look out for this with metal catalysts, as trace sulfur impurities can kill a reaction. It’s called “poisoning” which gives you an idea how tightly they bind.

2Gkashmiri 6y ago

sniff sniff I love the smell of petrol. Hmmm

andrelaszlo 6y ago

The Youtuber NileRed made a video about this. He explains why there are certain smells associated with metals and then makes some pure 1-octen-3-one in his lab. Very interesting! https://youtu.be/BqLH-nTZEOc https://youtu.be/BqLH-nTZEOc

Triv888 6y ago
It's a good video but I wonder if anyone ever made a large quantity of 1-octen-3-one using oil and metal instead (or whatever is from the skin...). It seems like it could be simpler.