[Donnah]

Hi Jdelgado!

Welcome.  I see you came in through the "back door"[)].

[Qing]

Hi, I'm only new here(as you can see),but I do have a question:-if it's really super-saturation why sometimes you can still smell it?

Qing

[Ians Daddy]

I'd have to say that the poot that just left you was just seconds before a part of you. Your olfactory nerves are a part of you as well. For a lack of a better term, it's simply your flavor.

[nilmot]

What's super-saturation means?

Tom

[Quantumcat]

Well, saturation is when there are too many of the molecules that are being dissolved for the water to keep them apart. Saturation is the point that the dissolved substance has exactly as many molecules as the water can possibly keep apart. I suppose super-saturation is when there are too many moleclues? I don't know really :-p

Am I dead? Am I alive? I'm both!

[jdelgado]

quote:Originally posted by nilmot

What's super-saturation means?

Tom

 
http://dictionary.reference.com/search?q=supersaturated [nofollow]

I once heard my chemistry professor use a rose as an example.  At first the fragrance can be sensed.  After repeated/constant smelling of the rose, your senses become supersaturated and you can no longer detect the smell.

[chris]

Don't confuse 'saturation' and 'adaptation'.

The human body is wired up to respond to things that change. You can demonstrate this for yourself by fixing your eyes on the screen in front of you and staring hard at only one spot. No matter how tempting it is to look away keep on looking. Before long your visual scene will beging to lose integrity and the image will begin to degrade in front of your eyes. If you move them it is immediately restored. Yours eyes continuously move to refresh the visual stimulus hitting the retina to prevent this kind of degradation.

The same mechanisms that allow your retina to adapt to an unchanging visual scene are also in play in your nose, in your mouth and on your skin. Get into a hot bath and intially it feels too hot to tolerate. But after a matter of seconds you are 'used' to it, and shortly after you are reaching for the hot tap to make it hotter still. These are examples of adaptation; you can think of it as the kiddie who gets bored with something after a short time and then needs a new stimulus to occupy him.

The point of these mechanisms is that our brain couldn't possibly cope with the barrage of information hitting it if everything were signalled on an absolute, proportional scale. That is, if a nerve cell were to fire every second when you were at 5 degrees, then 2x per second at 10 degrees and so on, we'd suffer neurological meltdown, information overload...call it what you will.

Instead the nervous system is most 'interested' in when things change, the obvious evolutionary advantage being that if something is changing it could signal danger.

The abililty to detect that something is changing relies on you being able to detect how much of something is present. So the difference between a strong smell and a weak smell is down to the number of odourant molecules which make up that smell. The more molecules, the stronger the smell. THat is until all of the receptors in your nose which are sensitive to that smell are filled up with smell molecules. After that you can add as many smell molecules as you like but the smell won't appear to change because your receptors for that particular odourant are 'saturated'.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[chris]

I'm sorry Quantum, but what I posted above is absolutely correct. Nerve cells habituate to change in a dynamic fashion, some rapidly, some more slowly. The same is true of the nose, taste, skin touch and temperature sensation.

In the context of the nose, of course the molecules diffuse away again, but under conditions of high concentration, like your seage farm, the olfactory receptors adapt to the continuous presence of the odourants, at whatever degree of receptor occupancy (saturating or not) and down-regulate their response.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Donnah]

I used to work at a bovine embryo transfer centre.  Everyone said I smelled like antiseptic and cow manure until showering and changing clothes, but I never noticed the smell.  It was really handy though, because if I wanted to do banking or grocery shopping I just did it on my way home from work and, like magic, many people left the lineup that I was in, so I sailed right through[]!

[Ians Daddy]

Ha ha ha...I'll have to remember that the next time I go to the bank. Now, where will I get some cow manure and antiseptic?

[Exodus (OP)]

One of my best friends is a farmer, he did a work placement on a local cow farm for two weeks and popped by for some lunch one day... BOY did he stink!

Resident Tour Operator - The Naked Scientists